Vaccines and Pregnancy: Safe Immunizations and Timing
When you're pregnant, every decision feels bigger. That’s why so many people ask: vaccines during pregnancy - are they safe? When should you get them? Which ones actually matter for your baby? The answer isn’t complicated, but it’s often buried under fear, outdated myths, or vague advice. The truth is simple: getting the right vaccines while pregnant doesn’t just protect you - it protects your newborn in their most fragile first months.
Why Vaccines During Pregnancy Are Different
Pregnancy changes your body in ways that make you more vulnerable to infections. Your immune system shifts to protect the growing baby, but that also means you’re less able to fight off things like the flu, whooping cough, or COVID-19. And here’s the critical part: when you get sick, your baby gets sick too - even before they’re born. The good news? Your body can pass protection to your baby through the placenta. Antibodies from vaccines you get during pregnancy cross over and give your newborn a shield they can’t get any other way. Babies under six months can’t get most vaccines themselves. So if you wait until after birth to get vaccinated, your baby is left exposed during the time they’re most at risk.The Four Vaccines You Need While Pregnant
There are four vaccines recommended during every pregnancy - not just once, but each time. These aren’t optional extras. They’re essential tools.- Influenza (flu) vaccine: This is an inactivated shot, not the nasal spray. It’s safe at any point during pregnancy, but the best time is early in flu season - around September or October. The CDC found that flu shots during pregnancy reduce the risk of flu-related hospitalization in mothers by 40% and cut infant flu infections by up to 63% in the first six months of life.
- Tdap (tetanus, diphtheria, pertussis): This is the whooping cough vaccine. It’s given between 27 and 36 weeks of pregnancy, ideally at 27-30 weeks. Why then? That’s when your body makes the most antibodies, and they have time to transfer to your baby. Studies show babies born to moms who got Tdap had 1.4 times higher levels of pertussis antibodies than their mothers. Without this vaccine, newborns face a 90% higher risk of severe whooping cough - and many end up in the ICU.
- COVID-19 mRNA vaccines (Pfizer-BioNTech or Moderna): These are safe and effective during pregnancy. Data from over 139,000 pregnant people in the CDC’s v-safe registry showed no increase in miscarriage, preterm birth, or birth defects. In fact, pregnant people who got vaccinated were 96% less likely to be hospitalized with severe COVID-19. Updated monovalent boosters are recommended as they become available.
- RSV vaccine (Abrysvo): Approved in May 2023 and recommended for use between 32 and 36 weeks during September through January, this vaccine cuts the risk of your baby needing medical care for RSV by 82% in the first 90 days after birth. RSV is the leading cause of infant hospitalization in the U.S. every winter - and this vaccine is changing that.
What Vaccines Should You Avoid?
Not all vaccines are safe during pregnancy. Live vaccines - those made with weakened versions of the virus - are avoided because of theoretical risks, even though no harm has ever been proven in humans.- MMR (measles, mumps, rubella)
- Varicella (chickenpox)
- Nasal flu vaccine (LAIV)
- Yellow fever (only if travel is unavoidable - talk to your provider)
How Effective Are These Vaccines for Your Baby?
It’s not just about whether you get the shot - it’s about whether your baby gets protected. Here’s what the numbers show:- Tdap: Antibodies in your baby’s cord blood are higher than yours. Protection lasts about 2-3 months, which is why your baby needs their own DTaP shots starting at 2 months.
- Flu: Babies under 6 months whose moms got the flu shot during pregnancy are 63% less likely to get confirmed flu. That’s the same level of protection as a flu shot in an adult.
- COVID-19: Babies born to vaccinated mothers had 61% lower risk of hospitalization for COVID-19 in their first six months, according to a 2023 study in The New England Journal of Medicine.
- RSV: The MATISSE trial showed 81.8% fewer cases of severe RSV in the first 90 days and 69.4% fewer through 6 months. That’s not just a small drop - it’s life-saving.
Side Effects? What to Expect
Most people feel nothing. Or maybe a sore arm. That’s it. The CDC’s v-safe registry tracked 139,897 pregnant people who got the COVID-19 vaccine. Of those, 84.6% had no pregnancy complications. The most common side effect? Injection site pain - reported by nearly 70%. Only 1.8% reported fever, and it didn’t last long. For Tdap, a Reddit thread with over 1,200 pregnant people showed 87% got the vaccine. Of those, 68% said the only side effect was mild arm soreness. Only 12% had concerns about ingredients - and most of those changed their minds after talking to their provider. RSV vaccine? A BabyCenter survey of 3,200 people found 92% reported no significant side effects. Of the 8% who did, it was a headache or tiredness that faded in a day or two. Serious reactions? Extremely rare. The FDA reports fewer than 1.2 adverse events per 10,000 doses for flu and Tdap vaccines during pregnancy. That’s lower than the rate for most common medications.When and How to Get Them
Timing matters. These aren’t vaccines you can take anytime.- Flu shot: Get it as soon as it’s available - usually July or August. Don’t wait until December. Flu season peaks in February, and you want protection in place.
- Tdap: Between 27 and 36 weeks. If you get it at 27 weeks, your baby gets the most antibodies. If you get it at 20 weeks, you get 37% fewer antibodies in your baby’s blood.
- RSV vaccine: Between 32 and 36 weeks, during September through January. If you’re due in March, you might need it in January. If you’re due in October, you might not need it at all - unless your provider says otherwise.
- COVID-19 booster: Get the latest version as soon as it’s available. No need to wait for a specific week. Just get it when you can.
What About Breastfeeding?
You can get all recommended vaccines while breastfeeding - even live ones like MMR or varicella. Your milk won’t carry the virus. But it will carry antibodies. That means your baby still gets some protection, even if they didn’t get it through the placenta. If you didn’t get Tdap or the flu shot during pregnancy, get them right after birth. You’ll still protect your baby - just not as completely as if you’d gotten them earlier.