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

Evan Walker
Evan Walker TheMediTary.Com |
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How safe and effective is the RSV vaccine during pregnancy? luza studios/Getty Images
  • 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 infects about 64 million people globally 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 the most common cause of 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 children ages 0 to 6 months.

For this reason, the Centers for Disease Control and Prevention (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.

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 at least two weeks prior.

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.

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 are less than 32 weeks pregnant. The FDA has this stipulation marked as a warning on the prescribing information for 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 nirservimab, 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 said monoclonal antibodies can 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.”

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