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Parents of newborns make great efforts to protect their babies from illness. They wash hands frequently, sterilize bottles, and screen family and friends for sickness before visits. It may seem like a lot, but they’re just following their doctors’ advice.

These steps are necessary because newborns don’t have a fully matured immune system. Infants begin receiving some of their standard vaccines at 2 months of age. However, babies are not eligible for other vaccines — including flu and COVID-19 — until 6 months of age.

Until babies can get all of their shots, they rely on their parents to protect them.

Protecting Infants From Disease

People who are pregnant or breastfeeding transfer antibodies they produce from vaccines to their babies. These antibodies help protect the infants until they’re old enough to receive their own shots.

Anne-Marie Rick, MD, MPH, PhD, is a newborn care physician at UPMC Children’s Hospital of Pittsburgh Primary Care Center and UPMC Magee-Womens Hospital. Her clinical research focuses on infectious diseases related to maternal-infant health. This includes:

• Sepsis (blood infections) in newborns.
• Transmission of COVID-19 right before or after birth.
• Vaccination during pregnancy or lactation and its impact (in utero and also through breastmilk) on infant antibodies.

Dr. Rick says there are three ways mothers can protect their babies from disease and infection.

1. Cocooning. If parents protect themselves against infectious disease, they are less likely to get infected. These steps protect the baby as well.
2. Transferred antibodies during pregnancy. When a pregnant person receives vaccines, they pass antibodies through the placenta to the baby. (The same happens with infection-acquired immunity, but it’s more dangerous because infections put parent and baby at risk.) Antibodies typically last three to six months after delivery, but sometimes longer than a year, Dr. Rick says.
3. Transferred antibodies through breast milk. “We have a long history of research related to how breast milk can protect against gastrointestinal illnesses in infants, such as rotavirus or norovirus,” Dr. Rick says.

How Do Maternal Vaccines Impact Babies?

When a pregnant person receives a vaccine during pregnancy, the antibodies they produce pass to the baby through the placenta. When a lactating person receives a vaccine, the antibodies they produce pass through to the baby through the breastmilk.

While a mother’s antibodies are present in newborns, doctors don’t yet know if they’re enough.

“We know the antibodies are there, we know they likely serve a really important role. But how much you actually need to protect a baby is unknown. That’s one of the goals of my research,” Dr. Rick says.

This is why it’s still so important to take extra precautions around newborns. When it comes to flu and COVID-19, the best protection for infants during the first six months of life is for their mother to be vaccinated and ideally providing breastmilk to their baby. But once infants are eligible for their own flu and COVID-19 vaccines, the best protection is for the child to be vaccinated.

“Although maternal vaccination and breastfeeding are key ways that parents can help protect their infants during the first few months of life, babies still remain vulnerable ” Dr. Rick says. “Even if mom is immunized, it is important that all children receive their own vaccines as soon as they become eligible to gain primary protection that is more robust and will last longer.”

COVID-19 and Infants

Everyone six months and older is now eligible for the COVID-19 vaccine. In fact, the CDC now recommends it for everyone older than six months. But how do you protect a newborn who can’t yet receive the COVID-19 shot?

Dr. Rick says vaccines are important for lactating mothers — and for pregnant people, no matter the stage of their pregnancy.

“We have no concerns for safety, even with first trimester, second trimester, and third trimester vaccinations for the COVID-19 vaccines that have been approved in the United States. There’s no reason to think that it can cause preterm birth or any significant harm to the fetus as it is developing,” she said.

She added that there are no concerns for future fertility or conception issues. “There’s universal recommendation for moms to get vaccinated, even if they’re pregnant or lactating.”

In fact, their real risk comes from not getting vaccinated. Pregnant women who contract COVID-19 have higher rates of preterm birth and other pregnancy complications.

Dr. Rick said breastfeeding mothers also shouldn’t hesitate to get vaccinated. The vaccine itself does not pass through the breastmilk, but the antibodies do.

Editor's Note: This article was originally published on October 3, 2022, and was last reviewed on July 12, 2023.