Overview

The COVID-19 pandemic was the most significant global health crisis since the 1918 Spanish Flu. Fortunately, the severity and lethality of COVID-19 have greatly diminished. The overall risk of severe illness or death from COVID-19 is now low, including for pregnant women. However, there is evidence that contracting COVID-19 during pregnancy may increase the risk of adverse outcomes such as preterm birth, cesarean delivery, preeclampsia or eclampsia, and blood clots. To reduce these risks and provide passive immunity to the baby, healthcare professionals recommend the COVID-19 vaccine for pregnant women. Deciding whether to get vaccinated during pregnancy can be challenging, as it requires weighing the potential risks and benefits.

This can be even more challenging with new vaccines that use innovative technology, where there is limited data and no long-term research yet available. Additionally, if you opt in to the COVID-19 vaccine you have choices regarding the type of vaccine and when to receive it. Learn about the available evidence on the safety, risks, and efficacy of COVID-19 vaccines during pregnancy so you can make an informed and confident decision.

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Vaccines

To better understand how vaccines work and the risks and benefits associated with them, let’s first cover some basics. Vaccines have come a long way since their inception in the 1790s. Traditionally, vaccines are made using a weakened or killed version of a disease-causing microorganism or parts of it, like its toxins or surface proteins. When given, typically through an injection, vaccines trigger your immune system to produce antibodies against the disease without causing illness. Essentially, the vaccine teaches your body to recognize and fight the disease if you encounter it in the future. In some cases, immunity lasts a lifetime; in others, booster shots may be necessary to maintain protection.

Immunity

Different forms of immunity can result from vaccination:

• Individual immunity occurs when a single person develops immunity after receiving a vaccine.
• Passive immunity happens when a pregnant mother passes antibodies to her baby through the placenta or later through breast milk. This is a big driver for vaccines recommended during pregnancy.
• Herd immunity occurs when a large portion of the population is vaccinated, reducing the spread of disease. Herd immunity is crucial for protecting individuals who cannot get vaccinated, such as those with compromised immune systems, allergies to vaccine ingredients, or babies too young to be vaccinated.

Evaluating Vaccines

I follow a systematic approach and conduct thorough research when evaluating any vaccine or medical intervention. I ask several key questions:

• What are the risks of the illness the vaccine is targeting?
• What is the history of the vaccine?
• What ingredients are in the vaccine?
• How effective is it?
• What are the risks and benefits?

In addition to these general questions, I consider personal factors like my current health status, the likelihood of exposure, where I live, places I may travel to, and the time of year. Answering these questions requires a significant amount of research and critical thinking.

The Controversy Surrounding Vaccines

Vaccines are a complex and often controversial topic. Researching vaccines is challenging, as it’s easy to come across information that appears unbiased but may ultimately push a pro- or anti-vaccine agenda.

This episode aims to provide an objective overview of the data so you can make an informed decision that’s right for you. I firmly believe that you should be able to choose whether or not you receive any vaccine or medical intervention. If you listen to this podcast, you can make an informed decision and not one based on fear.

The Role of the Centers for Disease Control and the World Health Organization 

The COVID-19 pandemic and response led to growing questions about the reliability of organizations like the CDC. In hindsight, it is clear there was mishandling of policies relating to things like testing and mask-wearing. The introduction of the COVID-19 vaccine and the push for Americans to get vaccinated raised concerns about the potential influence of pharmaceutical companies on these organizations.

It’s important to note that the CDC maintains the most extensive centralized databases for disease statistics in the United States, including for COVID-19. This organization focuses on protecting public health on a national scale. Its guidelines inform recommendations by bodies like the American College of Obstetricians and Gynecologists (ACOG), which, in turn, influence your healthcare provider’s advice. Understanding the information that informs your doctor’s or midwife’s recommendations will equip you to have an educated conversation with them and help you make the best decision for your pregnancy.

The General Consensus, Censorship, and Misinformation

There is no doubt that we have not seen such an aggressive campaign for a vaccine before COVID-19. The vaccine debate morphed into a political issue and a topic tied to personal freedom. National health organizations and governments aim to protect the most significant portion of the population possible. It is clear they believe vaccines are the best way to do that.

There was a massive campaign to eliminate misinformation about COVID-19 and the vaccines. Many individuals who spoke out against the vaccine were censored. Content creators, scientists, and doctors had YouTube videos removed, social media posts taken down, and web pages buried. In fighting misinformation, some portions of accurate information will also be lost. This makes researching COVID-19 vaccines incredibly challenging.

I know that was a lengthy introduction, and hopefully, this helps give some context to the complexity of this topic.

COVID-19

COVID-19 is a disease caused by the SARS-CoV-2 respiratory virus. When an infected person coughs, breathes, or sneezes, the virus can travel in aerosols in the air, which could be breathed in or land on a surface.

This novel virus emerged towards the end of 2019 and spread globally. Johns Hopkins Coronavirus Research Center tracked data until March of 2023 and reported 676 million cases of COVID-19 worldwide and over 6.8 million deaths. The COVID-19 pandemic was the worst global pandemic ever since the 1918 Spanish Flu. Fortunately, COVID-19 has significantly eased and is no longer as severe or deadly as it once was.

COVID-19 Symptoms

The possible symptoms of COVID-19 cover nearly any aspect of not feeling well and can appear anywhere between 2-14 days after exposure to the virus. Symptoms include fever, chills, cough, shortness of breath or difficulty breathing, sore throat, congestion or runny nose, new loss of taste or smell, fatigue, muscle or body aches, headache, nausea or vomiting, and diarrhea. Emergency warning signs include difficulty breathing, persistent pain or pressure in the chest, new confusion, or inability to wake or stay awake. Depending on skin tone, lips, nail beds, and skin may appear pale, gray, or blue, which indicates a lack of oxygen. Symptoms of COVID-19 and the flu are very similar, and the only way to know whether you have the flu or COVID-19 is to take a COVID-19 test.

Many cases of COVID-19 are asymptomatic, which means you have no noticeable symptoms. A systematic review and meta-analysis found 44.1% of cases were asymptomatic. If you are positive for SARS-CoV-2 but asymptomatic, you can still spread the virus to others.

COVID-19 During Pregnancy 

The overall risk of severe illness or death for COVID-19 is low, including for pregnant mothers. There is evidence that COVID-19 during pregnancy does increase your risk for other outcomes. COVID-19 during pregnancy raises your risk of preterm birth, cesarean birth, preeclampsia or eclampsia, and blood clots. Underlying health conditions, like obesity, diabetes, high blood pressure, and lung disease, increase the risks associated with COVID-19.

Emergency Use Authorization and FDA Approval of Vaccines

Historically, vaccines have taken a decade or longer to develop and get to market. Due to the severity and spread of COVID-19, there was a massive demand to get vaccines developed as quickly as possible. Pharmaceutical companies utilized government funding, previous research on SARS and MERS, and new vaccine technology to get vaccines to the public in under a year.

When specific criteria are met, the FDA can issue an emergency use authorization for a drug, vaccine, or treatment during a public health emergency. Those criteria include the FDA deeming the benefits outweigh the risks and that there are no adequate, approved, and available alternatives. Emergency use makes the approval process shorter and less involved than required for full FDA approval. There are three vaccines available for the 2024-25 COVID-19 season; two have full FDA approval, and one is available under an emergency use authorization.

How COVID-19 Vaccines Work 

In the past, all vaccines worked by introducing some part of a bacteria, virus, or pathogen into your body to trigger an immune response. Some of the vaccines developed for COVID-19 use a different approach.

mRNA Technology

Two available COVID-19 vaccines are mRNA vaccines, which use messenger ribonucleic acid (mRNA). mRNA carries genetic instructions from DNA to produce proteins. Unlike traditional vaccines that use bacteria or viruses, mRNA vaccines teach cells to make a protein that triggers an immune response, producing antibodies. COVID-19 has spike proteins that help it invade cells, and mRNA vaccines instruct cells to create a piece of this spike protein. The immune system then recognizes the protein and generates an antibody response, providing some immunity by preparing the body to recognize and fight off COVID-19 in the future. mRNA vaccines never enter the cell nucleus and cannot alter your DNA.

A benefit of using mRNA technology is these vaccines can be created more rapidly than other methods.

mRNA vaccines have been studied for decades, but none have been approved for use until recently. One potential risk is that this is a relatively new technology, and we lack long-term data on safety.

Protein Subunit Vaccines

One of the vaccine options available for COVID-19 does not use mRNA technology and is a subunit vaccine. Protein subunit vaccines introduce lab-made spike proteins of the virus and an adjuvant to stimulate a more robust immune response. This teaches the immune system to recognize and respond to the spike protein, preparing the body to fight the virus if exposed. This technology has been used for decades in many other vaccines, including hepatitis B, pertussis (whooping cough) in the Tdap vaccine, HPV (human papillomavirus), and some flu vaccines.

COVID-19 Vaccines During Pregnancy

The American College of Obstetricians and Gynecologists endorses the CDC recommendation that all eligible persons aged 6 months and older, including pregnant and lactating individuals, receive an updated 2024–2025 COVID-19 vaccine. Vaccination may occur in any trimester, and emphasis should be on vaccine receipt as soon as possible to maximize maternal and fetal health.

Developing Vaccine Antibodies During Pregnancy and Breastfeeding

Once you get the COVID-19 vaccine, it takes your body about two weeks to develop antibodies. A significant driver of any vaccine during pregnancy is to create passive immunity for your baby by passing antibodies to them in utero. The earliest your child could receive a COVID-19 vaccine is six months old, and maternal antibodies can give them some immunity in the first months of life.

There is evidence that after vaccination during pregnancy, COVID-19 vaccine-generated antibodies are present in umbilical cord blood samples and breast milk. This demonstrates that you pass antibodies to your baby through the placenta during pregnancy or through breast milk once they are born.

Breastfeeding significantly strengthens your newborn’s immune system and keeps them healthier overall. Even if your baby is getting formula and every meal isn’t breast milk, the antibodies you pass when you breastfeed are invaluable. Those could be vaccine-induced or naturally created antibodies.

Antibody Unknowns

We know you create antibodies and can pass them to your baby after a vaccine. What about antibodies from a natural COVID-19 infection? A study examined three groups of people to compare their antibody responses to COVID-19. 1. People who had a COVID-19 infection. 2. People who received an mRNA vaccine. 3. People who had both a COVID-19 infection and a vaccine (hybrid immunity).

All three groups developed antibodies. The group with a previous COVID-19 infection and the vaccine had the strongest and longest-lasting protection, especially against different virus variants. People with just a COVID-19 infection also had good protection, but their antibody levels weren’t as high. The group that received only the vaccine initially had strong protection, but their antibody levels dropped faster over time, especially for newer variants. Today, most people have likely been exposed to COVID-19 at some point over the last several years. Research shows similar results in pregnant mothers; the vaccine and boosters increase antibodies.

Staying Up to Date

SARS-CoV-2, like any virus, evolves and mutates over time. These mutations create different variants of the original virus. Similar to the flu vaccine, the COVID-19 vaccine is now updated annually to target new variants of the virus.

The messaging is consistent across health organizations to stay up to date with COVID-19 vaccines. You are up to date when you have received one dose of the 2024–2025 Moderna or Pfizer-BioNTech COVID-19 vaccine or one dose of the 2024–2025 Novavax vaccine unless you are receiving a COVID-19 vaccine for the very first time. If you have never received any COVID-19 vaccine and choose to get Novavax, you need two doses of the 2024–2025 Novavax COVID-19 vaccine to be up to date.

According to the CDC, getting the 2024–2025 COVID-19 vaccine is important because protection from the COVID-19 vaccine decreases with time, and COVID-19 vaccines are updated to give you the best protection from the currently circulating strains.

Different Vaccines Available

Three COVID-19 vaccines are currently either licensed or authorized under an Emergency Use Authorization by the U.S. Food and Drug Administration FDA. ACOG states there is no preferential recommendation for the use of any one COVID-19 vaccine over another. We will examine all three of your options.

Pharmaceutical companies are required to disclose a lot of information about vaccines. Once the FDA fully approves a vaccine, the Package Insert becomes available. Under emergency use authorization, information is disclosed in the Fact Sheet. There is a link to these documents for each vaccine, which contains a lot of data about the vaccine, clinical trials, efficacy, and safety.

Spikevax (2024–2025 Moderna COVID-19 Vaccine)

Full FDA Approval: for individuals aged 18 and older for both primary series and booster doses as of January 31, 2022.

Emergency Use Authorization: for children aged 6 months to 17 years as of June 17, 2022.

Type of vaccine: mRNA

Dose: Single dose or one dose at least 2 months after the last COVID-19 vaccine.

Vaccine efficacy: 93.2% efficacy in preventing COVID-19 and 98.2% efficacy against severe COVID-19.

Solicited Adverse reactions: Adverse reactions were reported in three age groups, 12-17, 18-24, and 65 and older. For the 18-24 age group the most commonly reported adverse reactions were pain at injection site (up to 86.3%), fatigue (up to 62.0%), headache (up to 58.9%), myalgia (up to 49.6%), arthralgia (up to 41.9%), chills (up to 40.3%), axillary swelling/tenderness (up to 24.8%), and nausea/vomiting (up to 16.7%).

Unsolicited Adverse Events Likely Associated with the Vaccine: Lymphadenopathy-related events were reported in 1.7% of vaccine recipients compared to 0.8% of placebo recipients. These events included conditions like swelling of inflammation of the lymph nodes and lumps under the armpit.

Hypersensitivity events like rash or hives at the injection site were reported by 6 participants in the SPIKEVAX group, with none in the placebo group. Delayed injection site reactions after 7 days, such as pain, redness, and swelling, were reported by 1.4% of vaccine recipients compared to 0.7% of placebo recipients.

Serious Adverse Events Likely Associated with the Vaccine: In the vaccine group, there were three serious adverse events of angioedema/facial swelling reported in individuals who had a history of receiving dermatological fillers.

There were two cases of myocarditis reported considered related to SPIKEVAX. There was one serious adverse event of erythema nodosum considered related to SPIKEVAX. Erythema nodosum is an inflammatory condition that causes painful, red nodules or bumps, usually located on the shins but sometimes found on other areas of the body, such as the arms or thighs.

Serious Adverse Events with Insufficient Information to Determine a Causal Relationship:

10 reports of facial paralysis (including Bell’s palsy) in the SPIKEVAX group and 4 in the placebo group. 72 reports of herpes zoster (shingles) in the SPIKEVAX group compared to 38 in the placebo group.

Postmarketing Experience: Reported adverse reactions include cardiac disorders (myocarditis and pericarditis), immune system disorders (allergic reactions and hives), and fainting. Because these reactions are reported voluntarily, it is not always possible to reliably estimate their frequency or establish a causal relationship to vaccine exposure.

Pregnancy Disclaimer: Available data on SPIKEVAX administered to pregnant women are insufficient to inform vaccine-associated risks in pregnancy.

Developmental Toxicity Study: In a developmental toxicity study the vaccine was administered to female rats on four occasions: 28 and 14 days prior to mating, and on gestation days 1 and 13. No vaccine-related fetal malformations or variations and no adverse effect on postnatal development were observed in the study.

Ingredients: Each 0.5 mL dose contains: Active Ingredient: 50 mcg nucleoside-modified mRNA. Lipids for mRNA delivery and protection: SM-102, Polyethylene glycol (PEG) 2000 dimyristoyl glycerol (DMG), Cholesterol, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). Buffers and Stabilizers to maintain the pH and stability of the vaccine: 0.25 mg tromethamine, 1.2 mg tromethamine hydrochloride, 0.021 mg acetic acid, 0.10 mg sodium acetate trihydrate: Cryoprotectant to protect the vaccine during freezing: 43.5 mg sucrose.

Comirnaty (2024–2025 Pfizer-BioNTech COVID-19 Vaccine)

Full FDA Approval: for individuals aged 12 and older for both primary series and booster doses as of August 23, 2021.

Emergency Use Authorization: for children aged 6 months to 11 years as of June 17, 2022.

Type of vaccine: mRNA

Dose: Single dose or one dose at least 2 months after the last COVID-19 vaccine.

Vaccine efficacy: The vaccine was 95% effective in preventing COVID-19 in participants without prior infection. Regardless of prior infection status, the vaccine’s efficacy was 90.9%.

Solicited Adverse reactions: Adverse reactions were reported in three age groups, 12-15, 16-55, and 56 and older. For the 16-55 age group the most commonly reported adverse reactions following any dose were pain at the injection site (88.6%), fatigue (70.1%), headache (64.9%), muscle pain (45.5%), chills (41.5%), joint pain (27.5%), fever (17.8%), and injection site swelling (10.6%)

Unsolicited Adverse Events:

Nausea (274 in vaccine group vs. 87 in placebo group), malaise (130 vs. 22), lymphadenopathy (83 vs. 7), asthenia (76 vs. 25), decreased appetite (39 vs. 9), hyperhidrosis (31 vs. 9), lethargy (25 vs. 6), and night sweats (17 vs. 3).

Unsolicited Adverse Events with Insufficient Information to Determine a Causal Relationship:

Bell’s palsy (facial paralysis) was reported by 4 participants in the COMIRNATY group and 2 participants in the placebo group. Currently available information is insufficient to determine a causal relationship with the vaccine.

Serious Adverse Events: no notable patterns of specific categories of serious adverse events that would suggest a causal relationship to COMIRNATY.

Postmarketing Experience: Cardiac Disorders: myocarditis, pericarditis Gastrointestinal Disorders: diarrhea, vomiting Immune System Disorders: severe allergic reactions, including anaphylaxis, and other hypersensitivity reactions (e.g., rash, pruritus, urticaria, angioedema) Musculoskeletal and Connective Tissue Disorders: pain in extremity (arm) Nervous System Disorders: syncope, dizziness. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to vaccine exposure.

Pregnancy Disclaimer: Available data on COMIRNATY administered to pregnant women are insufficient to inform vaccine-associated risks in pregnancy.

Developmental Toxicity Study: In a developmental toxicity study, the vaccine was administered to female rats on 4 occasions: 21 and 14 days prior to mating, and on gestation days 9 and 20. No vaccine-related adverse effects on female fertility, fetal development, or postnatal development were reported in the study.

Ingredients: Each 0.3 mL dose contains: Active Ingredient: 30 mcg of mRNA. Lipids for mRNA delivery and protection: 0.43 mg ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 0.05 mg 2-(polyethylene glycol 2000)-N,N-ditetradecylacetamide, 0.09 mg 1,2-distearoyl-sn-glycero-3-phosphocholine, 0.19 mg cholesterol. Buffers and Stabilizers to maintain the pH and stability of the vaccine: 0.06 mg tromethamine, 0.4 mg tromethamine hydrochloride. Cryoprotectant to protect the vaccine during freezing: 31 mg sucrose.

2024–2025 Novavax COVID-19 Vaccine

Full FDA Approval: n/a

Emergency Use Authorization: for individuals aged 12 and older as a primary series and booster option as of August 30, 2024.

Type of vaccine: Protein subunit

Dose: Two doses 3 weeks apart or one dose at least 2 months after the last COVID-19 vaccine.

Vaccine efficacy: The vaccine demonstrated an efficacy of 90.4% in preventing symptomatic mild, moderate, or severe COVID-19 among participants 18 years and older. There were no cases of moderate or severe covid in the participants that received the vaccine.

Solicited Adverse reactions: Adverse reactions were reported in two age groups, 18-64 and 65 and older. For the 18-64 age group the most commonly reported adverse reactions following any dose were injection site pain/tenderness (60.5-80.8%), fatigue/malaise (30.8-58.3%), muscle pain (24.1-50.7%), headache (26.2-47.1%), joint pain (7.9-23.4%), nausea/vomiting (6.7-12%), injection site redness (1-6.9%), injection site swelling (0.9-6.2%), and fever (0.4-6.2%).

Unsolicited Adverse Events:

The most frequently reported unsolicited adverse reactions were chills (0.4% vaccine recipients vs. 0.1% placebo recipients), lymphadenopathy-related reactions (0.3% vs. 0.1%), and injection site pruritus (0.1% vs. 0.0%). Lymphadenopathy-related reactions included lymphadenopathy, lymphadenitis, lymph node pain, and axillary pain.

Hypersensitivity reactions including urticaria, hypersensitivity, angioedema, and swelling of the face, lips, ear, and/or eyelids (0.1% vs. 0.03%)

Myocarditis and/or pericarditis were reported by two participants after the Novavax vaccine and no participants after placebo.

Serious Adverse Events with Insufficient Information to Determine a Causal Relationship:

Events of cardiomyopathy or cardiac failure were reported by eight participants after the Novavax vaccine and one participant after placebo.

An event of congestive cardiac failure was reported after the Novavax vaccine.

Events of acute cholecystitis (inflammation of the gallbladder) were reported by six participants after the Novavax vaccine and two participants after placebo.

11 participants who received the Novavax vaccine reported thrombotic and embolic events (non-cardiac, non-neurovascular) compared to 6 participants after placebo.

Events of uveitis (eye inflammation) were reported by 3 participants after Novavax vaccine and 2 participants after placebo.

For participants who received a third booster dose, there was one case of myocarditis.

Two serious adverse events in the injected arm were reported, including muscle edema and cellulitis of the injection site.

A serious adverse event of extensive deep vein thrombosis and pulmonary embolism was reported post booster in a 35-year-old female participant receiving oral contraceptive therapy.

In individuals who received a booster dose after three or more COVID-19 vaccinations two participants reported serious adverse events of cranial nerve palsy.

All of these events are reported with the disclaimer that currently available information is insufficient to determine a causal relationship with the vaccine. All events are under evaluation for potential causality and we will have more data once the Novavax vaccine received full FDA approval.

Postmarketing Experience: Cardiac Disorders: myocarditis, pericarditis Immune System Disorders: anaphylaxis Nervous System Disorders: paresthesia, hypoesthesia.

Pregnancy Disclaimer: Available data on the Novavax COVID-19 Vaccine, Adjuvanted administered to pregnant women are insufficient to inform vaccine-associated risks in pregnancy.

Developmental Toxicity Study: In a developmental toxicity study, the vaccine was administered to female rats on four occasions: 27 and 13 days prior to mating, and on gestational days 7 and 15. No vaccine-related adverse effects on female fertility, fetal development, or postnatal development were reported in the study. It should be noted that the vaccine in this toxicity study only contained one-fifth the quantity of adjuvant and other inactive ingredients.

Ingredients: Each 0.5 mL dose contains: Active Ingredient: 5 mcg recombinant spike protein. Adjuvant to enhance immune response: 50 mcg Matrix-M adjuvant (saponin extract from the soapbark tree). Additional Ingredients for stability, pH balance, and functionality: Cholesterol, Phosphatidylcholine, 3.85 mcg potassium dihydrogen phosphate, 2.25 mcg potassium chloride, 14.7 mcg disodium hydrogen phosphate dihydrate, 2.465 mg disodium hydrogen phosphate heptahydrate, 0.445 mg sodium dihydrogen phosphate monohydrate, 8.766 mg sodium chloride, 0.050 mg polysorbate 80, pH adjusted with sodium hydroxide or hydrochloric acid. Trace Residuals from the manufacturing process: Baculovirus and Sf9 cell proteins (≤ 0.96 mcg), Baculovirus and cellular DNA (≤ 0.00016 mcg), Lentil lectin (< 0.025 mcg), Methyl-α-D-mannopyranoside (2 mcg), Simethicone (< 0.92 mcg), Pluronic F-68 (< 2.19 mcg), Triton X-100 (< 0.025 mcg), Tergitol (NP9) (< 0.05 mcg).

Comparing Vaccine Options

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a vaccine cannot be directly compared with rates in the clinical trials of another vaccine and may not reflect the rates observed in practice. While we can’t exactly compare apples-to-apples when looking at efficacy rates of adverse effects, we can look at these from a 10,000-foot view to summarize how these vaccines stack up against each other. You will find manufacturer data and many links to research throughout this article. Please feel free to dig deeper into the evidence and draw your own conclusions.

Comparing Efficacy of COVID-19 Vaccines  

In clinical trials, vaccine efficacy is measured by giving some participants the vaccine and some participants a placebo and then measuring how many people get the virus. Since there are differences in the clinical trials, it isn’t exactly an apples-to-apples comparison. All three vaccines provide high levels of protection, particularly against severe disease, with some variation in overall efficacy and effectiveness across different age groups and variants. Comirnaty was 95% effective in preventing COVID-19 in participants without prior infection. Regardless of prior infection status, the vaccine’s efficacy was 90.9%. Spikevax had 93.2% efficacy in preventing COVID-19 and 98.2% efficacy against severe COVID-19. Novavax reported an efficacy rate of 90.4%.

Since the original clinical trials, there has been additional research on the effectiveness of the mRNA vaccines during pregnancy. Evidence shows efficacy rates during pregnancy align with efficacy seen in the non-pregnant population.

Comparing Adverse Effects

All three vaccines had high rates of side effects like injection site pain, swelling, redness, fatigue, muscle pain, headache, joint pain, nausea or vomiting, fever, and chills. All clinical trials specifically looked for these reactions following vaccine administration. These are common and expected side effects.

There are serious adverse events that are considered likely related to the vaccine. Events likely related to the vaccine and known risks include conditions like swelling or inflammation of the lymph nodes and lumps under the armpit, found in trials for all three vaccines. All three vaccines report cardiac disorders (myocarditis, pericarditis), immune system disorders (allergic reactions and hives, including anaphylaxis), and nervous system disorders like fainting or dizziness. Cases of facial swelling were reported in individuals who had a history of receiving dermatological fillers.

There are also many serious adverse events with insufficient information to determine a causal relationship. All three vaccines had cases of facial paralysis, including Bell’s palsy. Overall, Spikevax reported more serious adverse events than Comirnaty. This includes one serious event, an inflammatory condition likely associated with the vaccine, and higher rates of shingles in the vaccine group than in the placebo group.

Novavax reported more serious adverse events than Spikevax and Comirnaty, but none have sufficient information to determine a causal relationship. Some examples of conditions reported by Novavax include cardiomyopathy or cardiac failure in eight vaccine recipients and one placebo participant. Events of acute cholecystitis (inflammation of the gallbladder) were reported by six participants after the Novavax vaccine and two participants after the placebo. 11 participants who received the Novavax vaccine reported thrombotic and embolic events (non-cardiac, non-neurovascular) compared to 6 participants after placebo. Hopefully, we will have more information once this vaccine completes the trials and moves from emergency use authorization to full FDA approval.

Comparing Ingredients

COVID-19 vaccines contain more ingredients than many traditional vaccines, and some of these have long, complex names that can seem intimidating. However, it’s important to remember that each ingredient has undergone extensive safety testing and is approved for use in the small amounts included in vaccines.

The ingredients in the two mRNA vaccines are very similar and they both have mRNA as the active ingredient. There is some overlap in the ingredients but they do differ. Both the Pfizer and Moderna vaccines have lipids for mRNA delivery and protection, buffers and stabilizers to maintain the pH and stability of the vaccine and a cryoprotectant to protect the vaccine during freezing.

Since the Novavax vaccine is a subunit vaccine, its ingredients are quite different and there are more ingredients listed. The active Ingredient is a recombinant spike protein. Novavax includes an adjuvant to enhance immune response. There are additional ingredients for stability, pH balance, functionality, and trace residuals from the manufacturing process.

While it’s possible to spend a lot of time analyzing each ingredient in detail, let’s focus on the bigger picture. If you’re interested in a deeper dive, a summary of the ingredients for each vaccine is available for further review.

Choosing a Vaccine

Currently, both mRNA vaccines Comirnaty (Pfizer) and Spikevax (Moderna) have full FDA approval. More research is available on these than on the newer Novavax vaccine, which is authorized under emergency use authorization. Novavax is a protein subunit vaccine, which works more like other traditional vaccines rather than using newer mRNA technology. If you prefer not to get an mRNA vaccine, Novavax is an alternative, although there is less data available on its use during pregnancy. Please ask your doctor or midwife if you have questions about your vaccine options.

COVID-19 Vaccine Safety During Pregnancy 

All three vaccines have the disclaimer that available data on the vaccine administered to pregnant women are insufficient to inform vaccine-associated risks in pregnancy. All three also carried out developmental toxicity studies on rats. All studies administered the vaccine to rats four times, two before mating and two during gestation. All studies found no vaccine-related adverse effects on female fertility, fetal development, or postnatal development. All developmental toxicity studies used the human dose of the vaccine except for Novavax, which used a full dose of the active ingredient but one-fifth the quantity of adjuvant and other inactive ingredients.

The Research on the Safety of COVID-19 Vaccines During Pregnancy 

The initial clinical trials from the vaccine manufacturers did not include pregnant participants. Unfortunately, this is common in most research. We do have a lot of studies since the initial clinical trials, and overall, the data shows the vaccines are safe during pregnancy in the respect that vaccines do not cause higher rates of adverse outcomes for pregnant mothers and babies.

In a study of 84 pregnant women who got the Moderna or Pfizer vaccine. 11 were in the first trimester, 39 in the second trimester, and 34 in the third trimester. There was one preterm birth from a woman who went into labor at 35 weeks. The baby born preterm, and one additional baby was admitted to NICU. Otherwise, there were no adverse outcomes reported. The rate of babies born before 37 weeks in the U.S. is around 10%, and one study found the NICU admission rate for low-risk women to be between 6-9%.

One systematic review and meta-analysis compared the maternal, neonatal, and immunological outcomes between vaccinated and unvaccinated pregnant women. This included 37 studies with 141,107 pregnant women (36.8% vaccinated). Vaccination did lower the risk of COVID-19 infection and the risk of preterm birth. The study did find that COVID-19 vaccination may also be associated with higher odds of cesarean section. Unfortunately, there was no clear explanation for the higher cesarean rate.

Miscarriage

Miscarriage is extremely common in an average population. We would expect to see a miscarriage rate somewhere in the range of 10-15% in any study of the COVID-19 vaccines during pregnancy, in all stages, and especially including participants in the first trimester when miscarriages are more common.

The data shows there is not an overall increase in the risk of miscarriage with the COVID-19 vaccine during pregnancy. A systematic review and meta-analysis found compared to unvaccinated women, those who received the vaccine had a slightly higher risk of miscarriage, though this was not statistically significant. One study specifically examined miscarriage rates and found that being vaccinated within 28 days before a miscarriage did not increase your risk for miscarriage.

V-Safe Data

The CDC’s v-safe pregnancy registry tracked data between December 2020 to June 2021 of approximately 23,000 participants who reported getting a COVID-19 vaccine during pregnancy or within 30 days before their last menstrual period before the pregnancy. The CDC is still collecting data and requesting medical records for some participants.

In April 2021, CDC released the first U.S. data on the safety of mRNA COVID-19 vaccines administered during pregnancy. The CDC concluded that preliminary findings did not show obvious safety signals among pregnant persons who received mRNA COVID-19 vaccines. Although not directly comparable, the proportions of adverse pregnancy and neonatal outcomes (i.e., preterm birth, small size for gestational age, congenital anomalies, and neonatal death) among participants appear to be similar to the published incidences in pregnant populations studied before the COVID-19 pandemic.

The study notes that the registry data are preliminary, from a small sample, and describe mostly neonatal outcomes from third-trimester vaccination. The study was unable to evaluate adverse outcomes that might occur in association with exposures earlier in pregnancy, such as congenital anomalies, because no pregnant persons who were vaccinated early in pregnancy have had live births captured in the v-safe pregnancy registry to date.

While the CDC uses this study to state no obvious safety signals for the COVID-19 vaccine during pregnancy, this data really only supports no obvious safety signals with COVID-19 vaccination in the third trimester of pregnancy. Currently, ACOG and the CDC both state you can get the COVID-19 vaccine in any trimester, and ACOG emphasizes getting it as soon as possible during pregnancy.

More Data is Coming

Pfizer is in the final stages of a trial to study the vaccine in pregnant women. They initially hoped to enroll 4,000 healthy pregnant women to receive the vaccine between 24-34 weeks. The actual enrollment is just over 300 pregnant participants, half of which got the vaccine and half of which got placebo. There were two injections given, 21 days apart, from 24 to 34 weeks. This trial is reported as completed, but the final results have not yet been released.

Harvard began a study in 2021. This was planned as a five-year study, and as of October 2024, the status of this trial is still recruiting participants. Like the Pfizer trial, this study is expected to include 10,000 pregnant women who receive the vaccine, and the actual number of participants is expected to be much lower. They have concluded recruiting pregnant mothers who received the Spikevax or Comirnaty vaccine. If you plan to get the Novavax vaccine you can join this study and contribute to research that will help future mothers.

COVID-19 Vaccine and Fever

If you opt in to the COVID-19 vaccine, talk to your doctor or midwife about what to do if you get a fever. Fever is a common side effect of all of the available COVID-19 vaccines. In the clinical trials, it ranged from 0.4-17.8%. According to the American College of Obstetricians and Gynecologists, pregnant individuals who experience fever after vaccination should be counseled to take acetaminophen. Acetaminophen has been proven to be safe for use in pregnancy and does not appear to impact antibody response to COVID-19 vaccines.

Acetaminophen is an antipyretic, which is a medication that can reduce a fever. There is a past episode of the podcast about fevers in pregnancy and the use of acetaminophen. Some research challenges the use of acetaminophen during pregnancy, and you can learn more in this episode. If you plan to get a COVID-19 vaccine, talk to your doctor or midwife about how to treat fever and whether to take any antipyretic.

Combining the COVID-19 Vaccine with Other Vaccines During Pregnancy

When COVID-19 vaccines were first available, it was recommended not to get them within 14 days of another vaccine. That stance has changed, and ACOG states that COVID-19 vaccines may be administered simultaneously with other vaccines. This includes vaccines routinely recommended during pregnancy, such as influenza, respiratory syncytial virus (RSV), and tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap).

There is not much evidence on combining the COVID-19 vaccine with other vaccines in the same visit. Moderna did collect data on concomitant administration with the flu vaccine. 564 participants got Comirnaty with a flu vaccine, followed by a placebo shot one month later. The other group of 564 participants received the flu vaccine with a placebo shot, followed by Comirnaty one month later. Local and systemic adverse reactions were reported more frequently by participants who received COMIRNATY concomitantly with the influenza vaccine, compared to participants who received COMIRNATY alone. The most common adverse reactions reported were injection site pain, fatigue, and headache. Every vaccine comes with a risk of common side effects, and it does make sense that those risks would be increased if you combine multiple vaccines in one visit. You always have the option to space out vaccines if you prefer not to get multiple shots at once.

Making a Decision

We want assurance that any intervention is 100% safe, especially during pregnancy. This is where making informed decisions can be challenging. It is much easier to go with the flow of whatever your doctor or midwife recommends. It takes work to educate yourself on these topics, look at all the risks and benefits, and make a confident decision. Like any intervention, getting a vaccine should come with informed consent, which means you can opt out.

Vaccines are a challenging debate because you have to weigh the vaccine’s potential risks with the potential risks of the illness they are designed to protect you and your baby against. Ultimately, there is a risk no matter what you choose to do. Your job as a mother is to decide what risk you are comfortable with. Vaccines are not an all-or-nothing decision, and you may choose to get some vaccines and decline others.

Talk to Your Doctor or Midwife 

Please talk to your doctor or midwife if you have questions or concerns about the COVID-19 vaccine. If you decline the vaccine your care provider will likely bring it up again at a later prenatal visit. ACOG recommends that all clinicians provide strong recommendation for COVID-19 vaccination to their pregnant and lactating patients. ACOG states that for patients who do not receive any COVID-19 vaccine, the discussion should be documented in the patient’s medical record. During subsequent office visits, obstetrician-gynecologists should address ongoing questions and concerns and offer vaccination again.

This article provides a lot of evidence to help you decide whether the COVID-19 vaccine is the right choice for you. Even if you do not have a strong opinion after reading this, you should have a basic understanding and the confidence to have an educated conversation with your care provider.

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