RSV vaccine while pregnant: How effective is it and how does it work?

multiple units of rsv vaccine

  • RSV is a respiratory virus affecting about 64 million people around the world each year.

  • While RSV symptoms may only feel like a common cold to adults and older children, it can be much more serious in older adults, babies, and young children.

  • About 1.4 million children ages 0 to 6 months are hospitalized from RSV each year.

  • The CDC and American College of Obstetricians and Gynecologists both recommend pregnant people receive an RSV vaccine to help immunize their babies from the disease before they are born.

Respiratory syncytial virus (RSV) is a respiratory virus causing infection in the lungs, nose, and throat.

RSV affects all ages — including young infants — and infectsglobally each year.

While RSV symptoms normally feel just like those of the common cold in adults and older children, it can be a much more serious disease in older adults, young children, and babies.

Researchers report that RSV is theof hospitalization of infants in high-income countries.

The respiratory infection is responsible for about 3.6 million lower respiratory tract hospitalizations in young children each year, with 1.4 million of those in.

For this reason, the(CDC) and the American College of Obstetricians and Gynecologists (ACOG) both recommend pregnant people receive an RSV vaccine to help immunize their babies from the disease before birth.

RSV vaccine for pregnant people: How does it work? 

Of the two RSV vaccines currently available, only one vaccine — Pfizer’s Abrysvo — is approved by the(FDA) and European Commission for use in pregnant people.

The American College of Obstetricians and Gynecologists recommends the Abrysvo vaccine for people who are 32 to 36 weeks pregnant during the peak RSV season, which is from September to January in the U.S.

“A pregnant woman who receives (the) RSV vaccine in the last trimester — weeks 32 to 36 — will develop antibodies against RSV that will be passed to the fetus and protect the infant against RSV,” Dr. Edward Liu, chief of infectious diseases at Hackensack Meridian Jersey Shore University Medical Center in New Jersey explained to Medical News Today.

“Some infants are more susceptible to develop severe RSV symptoms that can lead to hospitalization, requiring oxygen and/or mechanical ventilation to help them breathe,” added Chanique Ecby, clinical assistant professor at the University of Houston Andy and Barbara Gessner College of Nursing. “Due to infants being so vulnerable, Abrysvo, the RSV vaccine for pregnant women, should be given to help provide antibodies that will protect the newborn against severe RSV disease after birth.”

How effective is the maternal RSV vaccine? 

The Abrysvo vaccine prevents lower respiratory tract disease and severe lower respiratory tract disease caused by RSV in infants from birth through 6 months of age.

Babies are protected by RSV at birth if the pregnant individual received the vaccine.

Dr. Sherry Ross, a board-certified OB/GYN and women’s health expert at Providence Saint John’s Health Center in Santa Monica, CA, spoke with MNT about RSV vaccine’s effectiveness:

“The effectiveness of the RSV vaccine in protecting a baby may vary depending on when the vaccine was given to the pregnant woman and the underlying health and lung conditions of the baby.”

In a study published in April 2023 of 3,500 pregnant individuals who received Abrysvo, the vaccine helped reduce the risk of severe lower respiratory tract disease by 81.8% within 90 days after birth and 69.4% within 180 days after birth, compared to those who received a placebo.

Additionally, in a subgroup of pregnant individuals receiving the vaccine during 32 to 36 weeks of pregnancy, lower respiratory tract disease risk was lowered by 34.7%, and severe lower respiratory tract disease risk was reduced by 91.1% within 90 days after birth when compared to those who received the placebo.

Dr. Patricia Faraz, a board-certified OB/GYN at The Women’s Hospital at MemorialCare Saddleback Medical Center in Laguna Hills, CA, told MNT the advantage of taking the vaccine during pregnancy allows a baby to be born with immunity and immediate protection, as long as the mom received a vaccine for greater than 14 days before the baby is born.

“Basically by giving it to the mom, you’re reducing one less vaccine that the baby needs to receive, and they have immediate immunity at birth,” Dr. Faraz added.

Potential side effects of RSV vaccine during pregnancy 

The FDA’s approval of Abrysvo for pregnant people was based on the results of a phase 3 clinical trial evaluating the vaccine’s safety and effectiveness.

“Potential side effects from the RSV vaccine are common and similar to other vaccines including injection site discomfort, headache, muscle pain, and nausea,” Dr. Ross explained. “There are no side effects to the unborn baby.”

Dr. Faraz noted that so far, pregnant people under her care receiving the vaccine have only experienced minimal side effects:

“The most common side effects would be pain or soreness at the injection site, and then other common side effects that have been reported are headaches, nausea, and muscle pain. Honestly, within my group of patients, I haven’t heard anybody complain about anything yet — so far it’s been well tolerated.”

What happens if a pregnant person does not get vaccinated?

There may be some instances in which a pregnant individual would not be able to receive the RSV vaccine.

For example, according to the CDC, the RSV vaccine should not be given to pregnant people who arepregnant. The FDA has this stipulation marked as a warning on thefor Abrysvo.

Early in the pregnancy before week 32, (the) RSV vaccine is not recommended as there are reports of preterm delivery,” Dr. Liu explained.

“A pregnant woman may be unable to receive the RSV vaccine … if she has a history of severe allergic reaction to any component of the vaccine,” Ecby added.

If a pregnant person is unable to get the RSV vaccine during pregnancy, Dr. Ross said the individual would be a perfect candidate to receive, which gives RSV antibodies directly to the baby after birth to protect against RSV infections:

“Nirsevimab gives RSV antibodies directly to the baby after birth, adding longer protection than the 6 months that the RSV vaccine affords a newborn. One disadvantage of nirsevimab is it may be harder to get, especially during the high-risk seasons of fall and winter.”

Dr. Faraz saidcan also be given to babies if they are born earlier than the two weeks needed for the vaccine to provide immunity:

“In a case where the baby was born, like let’s say a week after the mom was given the vaccine, that baby may still be a candidate to receive monoclonal antibodies after birth. This is (also) an option if you have a baby who was born with a cardiac defect. Even if the mom has been vaccinated, you could still administer the antibodies to the baby for added protection or a baby that severely immunocompromised.”

Should I get the RSV vaccine while pregnant?

Overall, all medical experts MNT spoke with agree that if a pregnant individual is able to take the RSV vaccine, they should.

“RSV is an infection that for years we know is a risk to small babies and infants,” Dr. Faraz said. “Their immunity is weak and RSV is … super common, especially when there are multiple children in the household — it’s just going to be so easy for that baby to get exposed.”

“Getting the RSV vaccine, between 32 and 36 weeks of pregnancy, is another way to ensure healthcare providers and pregnant women have done everything to give a baby the healthiest start in life, right out of the gate,” Dr. Ross added.

“There are no protective vaccines against RSV for babies as their immune systems are not mature,” Dr. Liu commented. “RSV seasons are unpredictable and can be severe regionally. RSV can be a serious infection for babies and taking the RSV vaccine can protect the baby.”

“If you meet the criteria for the vaccine, give your unborn child a fighting chance to be healthy during RSV season,” Dr. Ecby concluded.