Vaccines and Pregnancy: Safe Immunizations and Timing

When you’re pregnant, every decision feels bigger. What you eat, what you take, even the temperature of your coffee - it all matters. And when it comes to vaccines, confusion is common. Are they safe? When should you get them? Will they protect your baby, or put them at risk? The answers aren’t complicated, but they’re often buried under outdated myths and fear-based rumors. The truth is, vaccines during pregnancy aren’t just safe - they’re one of the most powerful tools you have to protect both yourself and your newborn.

Why Vaccines Matter During Pregnancy

Your immune system changes during pregnancy. It doesn’t shut down, but it does shift. That’s normal. But it also means you’re more vulnerable to certain infections. A bad case of the flu, whooping cough, or even COVID-19 can lead to serious complications - preterm labor, hospitalization, or worse. And your baby? They’re not born with protection against these diseases. Their own immune system won’t be ready to fight them off until they’re months old.

That’s where vaccines come in. When you get vaccinated while pregnant, your body makes antibodies. Those antibodies cross the placenta and give your baby a shield before they’re even born. It’s called passive immunity. And for newborns, it’s life-saving. Studies show that babies whose moms got the Tdap vaccine during pregnancy are 78% less likely to get whooping cough in their first two months. That’s critical because whooping cough can be deadly for infants under six months.

Which Vaccines Are Safe During Pregnancy?

Not all vaccines are created equal. Some are safe. Some aren’t. And the difference comes down to one thing: whether they contain live viruses.

Safe vaccines during pregnancy:

• Influenza (flu) vaccine - This is an inactivated shot, not the nasal spray. It’s safe in any trimester. Get it as soon as it’s available each year, ideally by October. The CDC found that during the 2020-21 flu season, pregnant people who got the flu shot were 40-60% less likely to be hospitalized with flu. And their babies? They had 41-63% less chance of getting the flu in their first six months.
• Tdap vaccine - This protects against tetanus, diphtheria, and pertussis (whooping cough). You need it during every pregnancy, between 27 and 36 weeks. Why then? That’s when your body produces the most antibodies, and they have the best chance to cross to your baby. Studies show babies born to moms who got Tdap at 27-30 weeks had 1.4 times more protective antibodies in their blood than those whose moms got it earlier.
• COVID-19 mRNA vaccines - Pfizer-BioNTech and Moderna are both recommended during pregnancy. Data from over 139,000 pregnant people in the CDC’s v-safe registry showed no increased risk of miscarriage, preterm birth, or birth defects. In fact, unvaccinated pregnant people were 96% more likely to be hospitalized with severe COVID-19 during the 2021 surge.
• RSV vaccine (Abrysvo) - Approved in 2023, this one-dose shot is given between 32 and 36 weeks during RSV season (September to January). It cuts the risk of your baby being hospitalized for RSV-related lung infections by 81.8% in the first 90 days of life. A 2023 study in the New England Journal of Medicine confirmed this protection lasts through six months.

Vaccines to avoid during pregnancy:

• MMR (measles, mumps, rubella)
• Varicella (chickenpox)
• Nasal flu spray (LAIV)
• Live attenuated vaccines in general

These contain weakened live viruses. Even though the risk is theoretical, they’re not recommended during pregnancy. If you need any of these, get them at least 28 days before you try to conceive.

Timing Matters - When to Get Each Vaccine

Getting the right vaccine at the wrong time can mean less protection for your baby. Here’s the ideal window for each:

• Flu shot - Anytime during pregnancy, but aim for September or October. Flu season runs October to May, and you want peak protection during the winter months.
• Tdap - Between 27 and 36 weeks. The sweet spot? 27 to 30 weeks. If you get it too early (before 20 weeks), your baby gets 37% fewer antibodies.
• COVID-19 vaccine - You can get it any time. If you’re in your first trimester and it’s been over 6 months since your last dose, talk to your provider about an updated booster.
• RSV vaccine - Only during September through January, and only between 32 and 36 weeks. Outside that window, it’s not effective.

Don’t wait until your last prenatal visit to ask. Bring it up at your 20-week checkup. Your provider should be ready to schedule it. If they aren’t, ask why. This isn’t optional care - it’s standard.

How Do We Know These Vaccines Are Safe?

The fear isn’t new. People worry about ingredients, long-term effects, or whether the vaccine will "overload" the baby. But here’s what the data says:

• Over 1.5 million pregnant people received the flu vaccine between 2010 and 2022 in the U.S. No safety concerns were found.
• Over 1.2 million pregnant people got Tdap. No link to birth defects, preterm birth, or low birth weight.
• The CDC’s v-safe pregnancy registry tracked 139,897 pregnant people who got COVID-19 vaccines. 84.6% had no pregnancy complications. The most common side effect? Sore arm.
• For the RSV vaccine, a study of 3,215 people on BabyCenter found 92% reported no side effects. Of the 8% who did, symptoms were mild - headache or tiredness - and gone in 1-2 days.

The World Health Organization reviewed 147 studies involving over 2.3 million pregnancies. Their conclusion? The benefits of these vaccines far outweigh any theoretical risks.

What About Breastfeeding?

If you’re breastfeeding, you’re not off the hook - but you don’t need to wait. All the vaccines listed above are safe while nursing. In fact, getting vaccinated while breastfeeding helps protect your baby through antibodies in your milk. It’s not as strong as placental transfer, but it still adds another layer of defense.

And if you missed a vaccine during pregnancy? Get it right after birth. The flu shot, Tdap, and COVID-19 vaccines are all safe while breastfeeding. You’ll protect yourself, and you’ll keep your baby safer too.

Common Concerns - And the Real Answers

• "Will the vaccine make me sick?" - The flu shot can’t give you the flu. The Tdap vaccine might cause soreness or a low-grade fever. That’s your immune system working, not the vaccine harming you.
• "What about aluminum or formaldehyde?" - These are in trace amounts, far below what your body handles naturally every day. Your body processes them without issue.
• "What if I’m allergic?" - If you’ve had a severe allergic reaction to a vaccine ingredient before, talk to your provider. But allergies to eggs, gelatin, or latex are rarely a problem with these vaccines.
• "Can I get all of them at once?" - Yes. You can get the flu shot, Tdap, and RSV vaccine during the same visit. No evidence shows that combining them reduces effectiveness or increases side effects.

What’s Next? The Future of Pregnancy Vaccines

The science is moving fast. A new vaccine for Group B Strep (GBS) is in Phase III trials and could be available by 2027. GBS is a leading cause of sepsis in newborns. A vaccine given during pregnancy could prevent thousands of cases.

There’s also a universal flu vaccine in development. Current flu shots change every year because the virus mutates. The new mRNA-based candidate could protect against multiple strains at once - meaning one shot per pregnancy might be enough.

Globally, only 15-25% of pregnant people in low-income countries get these vaccines. The WHO wants to raise that to 70% by 2030. Progress is happening - in the U.S., Tdap coverage jumped from 14% in 2012 to 60% in 2022. That’s thanks to better provider recommendations and clearer guidelines.

What to Do Now

If you’re pregnant right now:

1. Check your vaccination record. Did you get Tdap in your last pregnancy? You still need it again.
2. Ask your provider: "Which vaccines do I need now?" Don’t wait for them to bring it up.
3. Get the flu shot if it’s fall or winter. Get Tdap if you’re between 27-36 weeks. Get RSV if you’re in that window and it’s September-January.
4. Write down the vaccine name, date, and lot number. Keep it with your prenatal records.
5. If you’re unsure, ask for the CDC’s pregnancy vaccine fact sheets. They’re free, clear, and updated yearly.

Vaccines during pregnancy aren’t about taking risks. They’re about reducing them. They’re not optional extras - they’re essential care. Your body is doing something incredible: growing a human. Let science help you protect that miracle from the things that can hurt it.