Few medical decisions feel as high-stakes as choosing what goes into your body while you are growing another one. Pregnancy is a time of heightened vigilance — every food label gets scrutinized, every medication questioned, every Google search filtered through the lens of "but is it safe for the baby?" Vaccines are no exception. Surveys consistently show that vaccine hesitancy rises during pregnancy, even among people who are fully vaccinated outside of it.

The concern is understandable. But the science tells a clear and reassuring story: certain vaccines given during pregnancy are not only safe — they are among the most effective interventions available to protect both the pregnant person and their newborn during the most vulnerable period of life. Newborns cannot be vaccinated against most diseases for their first several weeks or months, yet they face the highest risk of severe complications from infections like influenza, pertussis, and respiratory syncytial virus (RSV). Maternal immunization bridges that gap by transferring protective antibodies across the placenta before birth.

This article walks through every vaccine that matters during pregnancy — what is recommended, what is safe if needed, what is contraindicated, and what the evidence actually shows. No scare tactics, no oversimplifications — just the data.

How Maternal Immunization Works: The Biology of Passive Immunity

To understand why vaccination during pregnancy is so powerful, you need to understand how a mother's immune system protects her newborn.

During pregnancy, the placenta does far more than deliver oxygen and nutrients. It also actively transports maternal immunoglobulin G (IgG) antibodies from the mother's blood into the fetal circulation. This process, called transplacental antibody transfer, begins around the second trimester and accelerates dramatically during the third trimester, with the majority of antibody transfer occurring after 28 weeks of gestation.

A 2019 study published in Nature Reviews Immunology described this as one of the most efficient selective transport systems in human biology. The neonatal Fc receptor (FcRn) on placental cells actively binds IgG antibodies and shuttles them across the placental barrier, achieving fetal antibody concentrations that can actually exceed maternal levels by the time of delivery.

These passively acquired antibodies provide the newborn with immediate protection — a borrowed immune defense that lasts for the first two to six months of life, gradually declining as the infant's own immune system matures and begins responding to its own vaccinations. This window is critical because:

  • Newborns have immature immune systems that respond poorly to most vaccines
  • The first doses of many childhood vaccines are not given until 6-8 weeks of age
  • Even after the first dose, it takes multiple doses to build full protection
  • Diseases like pertussis, influenza, and RSV are most dangerous in the first months of life

Maternal vaccination exploits this biology deliberately. By vaccinating the pregnant person at the right time — typically during the third trimester — you ensure peak antibody levels at the time of maximum placental transfer, producing a newborn who enters the world with a ready-made immune arsenal against specific threats.

A 2022 meta-analysis in The Lancet Infectious Diseases examining 48 studies confirmed that maternal vaccination produces measurable protective antibodies in cord blood for pertussis, influenza, COVID-19, and RSV, with effectiveness against infant disease ranging from 35% to 91% depending on the pathogen and timing of vaccination.

Tdap: The Most Important Vaccine in Pregnancy

If there is one vaccine that every obstetric guideline in the world agrees on, it is Tdap — the combined tetanus, diphtheria, and acellular pertussis vaccine. The pertussis (whooping cough) component is the primary reason it is recommended during every pregnancy, regardless of prior vaccination history.

Pertussis is extraordinarily dangerous for newborns. According to the CDC, infants under 2 months of age account for the majority of pertussis-related hospitalizations and nearly all pertussis deaths. The disease causes violent, uncontrollable coughing spasms that can lead to apnea (cessation of breathing), pneumonia, seizures, brain damage, and death. Infants are too young to have received their own pertussis vaccination (the DTaP series begins at 2 months), leaving a dangerous gap.

Maternal Tdap vaccination fills that gap. The American College of Obstetricians and Gynecologists (ACOG), the CDC, and the WHO all recommend Tdap during each pregnancy, ideally between 27 and 36 weeks of gestation. This timing is not arbitrary — it is precisely calibrated to produce peak maternal antibody levels during the period of maximum transplacental transfer.

The evidence supporting this strategy is robust:

  • A 2017 study in Clinical Infectious Diseases analyzed data from over 148,000 infants and found that maternal Tdap vaccination was 91% effective at preventing pertussis in infants under 2 months of age.
  • A 2020 systematic review in Vaccine pooling data from multiple countries found effectiveness of 78% against infant pertussis infection and 90% against pertussis-related hospitalization in the first three months of life.
  • A 2014 study in JAMA found that among infants who did develop pertussis despite maternal vaccination, the disease was significantly less severe — shorter hospitalizations, fewer complications, and no deaths.

The recommendation to vaccinate during every pregnancy — even pregnancies spaced only a year apart — reflects the fact that pertussis antibodies wane relatively quickly. Each pregnancy requires a fresh boost to ensure adequate antibody levels for transfer.

Common side effects are mild: injection site pain and swelling, low-grade fever, and fatigue. Large safety studies, including a 2018 cohort study in JAMA examining over 626,000 pregnancies, have found no increased risk of adverse pregnancy outcomes including preterm birth, low birth weight, or stillbirth.

Influenza Vaccine: Protection for Two

Influenza vaccination is recommended for all pregnant people during flu season, at any point during pregnancy. Both ACOG and the CDC classify pregnant individuals as a high-risk group for severe influenza complications, and the data explains why.

Pregnancy causes significant changes to the immune system, cardiovascular system, and respiratory system. The immune system shifts toward a more tolerant state (to avoid rejecting the fetus), the heart pumps up to 50% more blood, and the expanding uterus pushes the diaphragm upward, reducing lung capacity. These changes make pregnant people more susceptible to severe illness from respiratory viruses.

A 2019 meta-analysis in BMC Infectious Diseases analyzing data from multiple influenza seasons found that pregnant people were significantly more likely to be hospitalized with influenza and had a higher rate of ICU admission compared to non-pregnant adults of the same age. The 2009 H1N1 pandemic provided a stark illustration: pregnant people accounted for approximately 5% of all H1N1-related deaths in the United States despite representing roughly 1% of the population.

Beyond protecting the pregnant person, the flu vaccine provides substantial newborn protection. A 2014 randomized controlled trial published in The New England Journal of Medicine, conducted across multiple sites in South Africa, Nepal, and Mali, found that maternal influenza vaccination reduced laboratory-confirmed influenza in infants during the first six months of life by 63%. Infants under 6 months cannot receive the flu vaccine themselves, making maternal vaccination the only route to early protection.

Key points about influenza vaccination in pregnancy:

  • Only the inactivated influenza vaccine (the shot) is recommended during pregnancy. The live attenuated influenza vaccine (nasal spray, FluMist) is contraindicated in pregnancy because it contains live, weakened virus.
  • Vaccination is recommended at any trimester — there is no need to wait for the third trimester. In fact, early vaccination may be preferable if flu season has already begun.
  • A 2023 Cochrane review confirmed that influenza vaccination during pregnancy does not increase the risk of miscarriage, stillbirth, preterm birth, congenital anomalies, or low birth weight.
  • Thimerosal-free formulations are widely available for those who prefer them, though the CDC and WHO note that thimerosal-containing vaccines have been extensively studied and shown to be safe during pregnancy.

COVID-19 Vaccines: What Three Years of Data Have Shown

COVID-19 vaccination during pregnancy was initially met with caution — the first-generation mRNA vaccines were authorized through emergency use in late 2020, and pregnant people were excluded from the initial clinical trials. This left an evidence gap that fueled hesitancy. Three years and millions of vaccinated pregnancies later, the picture is clear.

The risk of unvaccinated COVID-19 in pregnancy is substantial. A 2022 systematic review published in The BMJ analyzing 120 studies and over 1.3 million pregnant individuals found that SARS-CoV-2 infection during pregnancy was associated with significantly increased risks of preeclampsia, preterm birth, stillbirth, ICU admission, and maternal death. The risk was highest for those infected in the third trimester.

The safety data is now extensive. The CDC's V-safe surveillance system and the Vaccine Safety Datalink have tracked hundreds of thousands of pregnant individuals who received mRNA COVID-19 vaccines. Key findings include:

Maternal antibody transfer occurs effectively. Multiple studies have demonstrated that mRNA vaccination produces robust anti-SARS-CoV-2 antibodies in cord blood. A 2022 study in JAMA Pediatrics found that vaccination during the third trimester produced the highest cord blood antibody levels, and that maternal vaccination was 61% effective at preventing COVID-19 hospitalization in infants under 6 months.

Current guidelines from ACOG and the CDC recommend that pregnant individuals receive an updated COVID-19 vaccine when one is available, at any stage of pregnancy. Those who are unvaccinated should receive a primary series as well.

The fertility misinformation that circulated on social media — claiming COVID-19 vaccines cause infertility — has been thoroughly debunked. A 2022 study in Human Reproduction involving over 2,000 couples trying to conceive found no difference in fertility rates between vaccinated and unvaccinated individuals.

RSV Vaccine (Abrysvo): The Newest Addition

In September 2023, the FDA approved Abrysvo (manufactured by Pfizer) — the first vaccine ever approved specifically for use during pregnancy to protect newborns from respiratory syncytial virus (RSV). This marked a milestone in maternal immunization.

RSV is the leading cause of hospitalization in infants under 12 months of age worldwide. According to a 2022 study in The Lancet, RSV causes an estimated 3.6 million hospitalizations and 101,400 deaths annually in children under 5, with the greatest burden falling on infants in their first six months of life — before any pediatric RSV prevention (such as the monoclonal antibody nirsevimab) can take full effect.

Abrysvo is a bivalent RSV prefusion F protein vaccine. The pivotal trial (MATISSE), published in The New England Journal of Medicine in 2023, enrolled approximately 7,400 pregnant participants across 18 countries. Key results:

  • 82% efficacy against severe RSV-associated lower respiratory tract illness in infants through 90 days of life
  • 69% efficacy through 180 days of life
  • No significant safety signals for the pregnant participants or their infants
  • The most common side effects were injection site pain and headache

ACOG and the CDC recommend Abrysvo for pregnant individuals at 32 through 36 weeks of gestation, administered between September and January in the Northern Hemisphere (during RSV season). The vaccine is given as a single dose — no booster required.

It is worth noting that Abrysvo is offered as an either/or option alongside nirsevimab (Beyfortus), the monoclonal antibody given directly to infants after birth. Both provide RSV protection, but through different mechanisms. Most infants should receive one or the other — if the pregnant person received Abrysvo less than 14 days before delivery, the infant should receive nirsevimab instead, as there may not have been sufficient time for antibody transfer.

The addition of RSV prevention to the maternal vaccine toolkit is a significant advance, and clinical guidelines are still evolving as real-world data accumulates.

Vaccines That Are Contraindicated During Pregnancy

Not all vaccines are safe during pregnancy. The critical distinction is between inactivated vaccines (which contain killed virus, viral fragments, or purified proteins) and live vaccines (which contain weakened but replicating virus). As a general rule, live vaccines are contraindicated during pregnancy because of a theoretical risk that the weakened virus could cross the placenta and infect the fetus.

The following vaccines should not be given during pregnancy:

MMR (Measles, Mumps, Rubella)

The MMR vaccine is a live attenuated vaccine and is contraindicated during pregnancy. Women should wait at least four weeks after MMR vaccination before becoming pregnant. However, if a non-immune pregnant person is exposed to rubella, the risk of congenital rubella syndrome (which can cause deafness, heart defects, cataracts, and intellectual disability in the baby) is the reason rubella immunity is routinely checked at the first prenatal visit. If a pregnant person is found to be non-immune to rubella, they should receive MMR immediately postpartum, before hospital discharge.

Importantly, accidental MMR vaccination during pregnancy — which occasionally happens before pregnancy is recognized — has not been shown to cause harm. The CDC's registry of inadvertent MMR vaccinations during pregnancy found no cases of congenital rubella syndrome, though the vaccine remains contraindicated as a precaution.

Varicella (Chickenpox)

The varicella vaccine is also a live vaccine and is contraindicated during pregnancy. Varicella infection during pregnancy, particularly during the first or second trimester, can cause congenital varicella syndrome — a rare but serious condition involving skin scarring, limb abnormalities, and neurological deficits. Women should wait at least four weeks after varicella vaccination before becoming pregnant.

Non-immune pregnant people exposed to varicella should receive varicella-zoster immune globulin (VZIG) — a passive antibody product that is safe during pregnancy — rather than the vaccine.

Live Attenuated Influenza Vaccine (LAIV / FluMist)

As noted above, only the inactivated influenza shot is appropriate during pregnancy. The nasal spray version contains live virus.

HPV Vaccine

The HPV vaccine (Gardasil 9) is not recommended during pregnancy, though it is not a live vaccine. This is a precautionary recommendation due to insufficient data, not because of any demonstrated harm. If a woman discovers she is pregnant after starting the HPV series, the remaining doses should be delayed until after delivery. No intervention is needed if a dose was inadvertently given during pregnancy.

Other Live Vaccines

Additional live vaccines that should generally be avoided include BCG (tuberculosis), yellow fever, and oral typhoid vaccine. However, in situations where the risk of infection is high (such as travel to a yellow fever endemic area), the risk-benefit calculation may favor vaccination — these decisions should be made individually with a healthcare provider.

Vaccines That Are Safe When Indicated

Beyond the routinely recommended vaccines (Tdap, influenza, COVID-19, and RSV), several other vaccines may be given during pregnancy when there is a specific clinical indication:

Hepatitis B — The hepatitis B vaccine is an inactivated (recombinant) vaccine and is safe during pregnancy. It is recommended for pregnant people at risk of hepatitis B infection, such as healthcare workers, people with household or sexual contact with an HBV-infected individual, or those with multiple sexual partners. ACOG supports its use when indicated.

Hepatitis A — Also an inactivated vaccine and considered safe during pregnancy. Recommended for pregnant people traveling to endemic areas or with other risk factors.

Pneumococcal vaccines — Both the polysaccharide (PPSV23) and conjugate (PCV20) vaccines are inactivated and can be given during pregnancy if clinically indicated, such as for pregnant people with asplenia, immunocompromising conditions, or chronic lung disease.

Meningococcal vaccines — Inactivated meningococcal conjugate (MenACWY) and serogroup B (MenB) vaccines may be given during pregnancy if there is an increased risk of meningococcal disease, such as during an outbreak or for those with complement deficiencies.

Rabies — The rabies vaccine is inactivated and can be given during pregnancy following animal exposure. Given the nearly 100% fatality rate of rabies, pregnancy is never a reason to withhold post-exposure prophylaxis.

The general principle: inactivated vaccines pose no known risk to the fetus and should be given during pregnancy whenever the benefit outweighs the theoretical risk of withholding them. The real danger is often the disease itself, not the vaccine.

Optimal Timing: When to Get Each Vaccine

Timing matters for maximizing both maternal protection and antibody transfer to the newborn. Here is a summary of the recommended schedule:

Vaccine When During Pregnancy Notes
Tdap 27-36 weeks (early third trimester) Every pregnancy, regardless of prior Tdap
Influenza (inactivated) Any trimester during flu season Ideally before flu season peaks
COVID-19 Any trimester Updated formulation when available
RSV (Abrysvo) 32-36 weeks, September-January Single dose; OR infant gets nirsevimab
Hepatitis B Any trimester (if indicated) Complete series if time allows

For Tdap and RSV, the third-trimester timing window is specifically designed to maximize antibody transfer. Antibodies need approximately two weeks to reach peak levels after vaccination and then require several additional weeks to cross the placenta in sufficient quantities. Vaccinating too late — within days of delivery — may not allow enough time for full antibody transfer.

For influenza and COVID-19, the priority is maternal protection, which begins within two weeks of vaccination regardless of gestational age. Waiting until the third trimester to get a flu shot during an active flu season puts the pregnant person at unnecessary risk.

Keeping track of multiple vaccine dates alongside prenatal appointments, lab work, and other pregnancy milestones can be overwhelming. WatchMyHealth's medication and appointment tracking features make it easy to log each vaccine dose, set reminders for upcoming shots, and keep a complete record that you can share with your healthcare provider at each visit.

Addressing Vaccine Hesitancy: Common Concerns and What the Data Says

Vaccine hesitancy during pregnancy is common and not irrational — it stems from a deep protective instinct. But it is important to separate evidence-based caution from fear-driven avoidance. Here are the most common concerns and what the research shows.

"The vaccines haven't been tested enough in pregnant people."

This was a legitimate concern for COVID-19 vaccines in early 2021. It is no longer accurate. As of 2025, hundreds of thousands of pregnant people have been studied across multiple vaccine types. The CDC's V-safe program alone enrolled over 35,000 pregnant participants for COVID-19 vaccine monitoring. Tdap and influenza vaccines have decades of safety data in pregnancy. The RSV vaccine (Abrysvo) included approximately 3,700 pregnant participants in its pivotal trial. Every major vaccine recommended during pregnancy has been evaluated through large-scale observational studies, randomized controlled trials, or both.

"I don't want to overload my immune system while pregnant."

The concept of immune "overload" does not reflect how the immune system works. A 2002 landmark paper in Pediatrics by Dr. Paul Offit calculated that the human immune system is capable of responding to approximately 10,000 antigens simultaneously. A typical vaccine contains a tiny fraction of the antigens that a person encounters simply by breathing, eating, and touching surfaces every day. Pregnancy does alter immune function — shifting toward a Th2-dominant response — but this does not impair the ability to respond to inactivated vaccines.

"I'd rather wait until after the baby is born."

This approach misses the entire point of maternal immunization. Postpartum vaccination protects the mother but does not transfer antibodies to the baby. The passive immunity mechanism requires vaccination before delivery so that antibodies can cross the placenta during pregnancy. Once the baby is born, the placental connection is gone. Breastfeeding does transfer some antibodies (primarily IgA), but this provides mucosal protection, not the systemic IgG protection that prevents severe disease.

"Natural immunity is better."

For some diseases, surviving natural infection does produce durable immunity. But this argument ignores the cost of acquiring that immunity. Pertussis can kill a newborn. Influenza during pregnancy increases the risk of preterm birth and maternal death. COVID-19 in pregnancy is associated with preeclampsia and stillbirth. The question is not whether natural immunity is "better" in the abstract — it is whether the risk of the disease is acceptable when a safe vaccine alternative exists. For the diseases targeted by maternal immunization, the answer is clearly no.

"I've read about side effects."

Vaccines, like all medical interventions, have side effects. The common ones — injection site soreness, mild fever, fatigue — are temporary and reflect the immune system mounting a response. Serious adverse events are exceedingly rare and are tracked through multiple surveillance systems (VAERS, V-safe, the Vaccine Safety Datalink, and international equivalents). The risk of a serious vaccine reaction is orders of magnitude lower than the risk of serious complications from the diseases these vaccines prevent.

Postpartum and Breastfeeding: What Changes After Delivery

The postpartum period is an important time to catch up on any vaccines that were contraindicated during pregnancy.

MMR and varicella should be given immediately postpartum to any person found to be non-immune during prenatal testing. There is no need to wait — both vaccines are safe during breastfeeding. Live vaccines are safe for breastfeeding mothers because the weakened vaccine viruses are not transmitted through breast milk in clinically significant amounts (with the sole exception of the smallpox vaccine, which is not routinely used).

HPV vaccine series can be started or resumed postpartum.

All inactivated vaccines are safe during breastfeeding.

Breastfeeding itself provides additional immune benefits through the transfer of secretory IgA antibodies, lactoferrin, and other immune factors. A 2021 study in JAMA Pediatrics demonstrated that breast milk from people vaccinated against COVID-19 during pregnancy or postpartum contained SARS-CoV-2-specific antibodies for up to six months, providing an additional layer of mucosal protection for the breastfed infant.

Vaccination of household contacts — partners, grandparents, siblings, and caregivers — is another critical strategy. This "cocooning" approach reduces the infant's exposure to vaccine-preventable diseases during the vulnerable first months of life. All household contacts should be up to date on Tdap, influenza, and COVID-19 vaccines before the baby arrives.

Special Situations: High-Risk Pregnancies, Travel, and Outbreaks

Certain circumstances require additional vaccine considerations during pregnancy.

Immunocompromised pregnant individuals — People with HIV, organ transplants, autoimmune conditions requiring immunosuppressive therapy, or other immunocompromising conditions may have a reduced response to vaccines but are at even higher risk from vaccine-preventable diseases. Inactivated vaccines are generally safe in this population, but live vaccines remain contraindicated. An infectious disease specialist should be involved in vaccine planning.

Travel during pregnancy — International travel may necessitate additional vaccines. Hepatitis A, hepatitis B, meningococcal, and inactivated polio vaccines can all be given during pregnancy when indicated by travel destination. Yellow fever vaccine (a live vaccine) is generally contraindicated but may be considered if travel to a high-risk area is unavoidable — the WHO states that the risk of yellow fever disease in an endemic area may outweigh the theoretical risk of the live vaccine.

Disease outbreaks — During outbreaks of hepatitis A, meningococcal disease, or other vaccine-preventable infections, the threshold for vaccinating pregnant individuals is lower. Public health authorities may issue specific guidance for pregnant people during outbreaks.

Rh immunoglobulin (RhoGAM) — While not a vaccine, RhoGAM is an important immunological product given during pregnancy to Rh-negative individuals carrying an Rh-positive fetus. It prevents Rh sensitization and is safe to give alongside any vaccine.

The overarching principle: pregnancy is a reason to carefully consider the timing and type of vaccine, not a reason to avoid vaccination entirely. The diseases these vaccines prevent are more dangerous to a pregnancy than the vaccines themselves.

What to Discuss With Your Healthcare Provider

Every pregnancy is different, and vaccine recommendations should be individualized based on your medical history, gestational age, the time of year, local disease prevalence, and any planned travel.

At your first prenatal visit, your provider should:

  • Review your immunization history
  • Check your immunity to rubella and varicella (typically through blood tests)
  • Screen for hepatitis B surface antigen
  • Discuss the timing of Tdap, influenza, and COVID-19 vaccines
  • Ask about any planned travel that might require additional immunizations

Questions worth asking your provider:

  • Am I immune to rubella and varicella?
  • When should I get my Tdap this pregnancy?
  • Should I receive the RSV vaccine (Abrysvo), or will my baby receive nirsevimab after birth?
  • Is it flu season, and have I received this year's influenza vaccine?
  • Am I up to date on my COVID-19 vaccination?
  • Are there any vaccines my partner or household contacts should get before the baby arrives?

WatchMyHealth can help you prepare for these conversations by keeping all your health data in one place. Log your vaccination history, track any symptoms after vaccination, and bring a clear record to every prenatal appointment so nothing falls through the cracks.

The Bottom Line

Maternal immunization is one of the most elegant strategies in modern medicine: a single intervention that protects two patients simultaneously. The recommended vaccines during pregnancy — Tdap, influenza, COVID-19, and now RSV — have been studied extensively and have strong safety profiles. The live vaccines that are contraindicated (MMR, varicella) can and should be given immediately after delivery if needed.

The evidence is not ambiguous. Pertussis kills newborns who could have been protected by a third-trimester Tdap shot. Influenza sends pregnant people to the ICU at disproportionate rates. RSV fills pediatric hospitals every winter with infants who cannot yet protect themselves. Vaccination during pregnancy is not about taking a risk — it is about reducing one.

If you are pregnant or planning a pregnancy, talk to your healthcare provider about your vaccine status. If you are hesitant, ask questions — good providers welcome them. And if someone shares misinformation about vaccines and pregnancy, point them toward the data. The science is clear, the surveillance is ongoing, and the goal is simple: a healthy pregnancy and a protected newborn.