Key Takeaways

The Food and Drug Administration (FDA)has approvedthe first shot to prevent respiratory syncytial virus (RSV) in infants.

Infants will receive one dose of the immunization, called Beyfortus, either at birth or before their first RSV season.TheCDChas recommended the shot for infants under 8 months old, as well as older infants still at risk of severe RSV.

“With the demonstrated strong safety and efficacy results, I would recommend this vaccine for all infants and children since RSV disease is widespread, and especially harmful to infants and children under 5,”Yvonne Maldonado, MD, division chief of pediatric infectious diseases at Stanford Medicine Children’s Health, told Verywell Health via email.

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Why an Infant RSV Shot Matters

Currently, RSV is a leading cause of infant hospitalizations in the U.S. About 100–300 babies and children under the age of five die each year from severe complications of RSV that can lead to pneumonia and bronchiolitis.

The Sanofi and AstraZeneca vaccine is the first treatment to protect infants from severe complications from RSV, and can change the landscape in the battle against rising hospitalizations due to severe respiratory illness.

What Is RSV?

RSV is a contagious virus that causes respiratory illness and fluid-build up in the lungs.

While most infants are able to battle RSV on their own without much intervention, certain health conditions can put babies at a higher risk for developing severe and sometimes deadly respiratory symptoms.

Infants and children at high risk of hospitalization from RSV include:

“When babies breathe, they breathe through lung tubes that are many times smaller than those of adults,”Iona Munjal, MD, vaccine research and development maternal RSV global clinical lead at Pfizer, told Verywell via email. “Fluid build-up can almost completely occlude their breathing airways and fill up their lungs with concerning levels of inflammation and fluid.”

How Effective Is the Infant Immunization?

Results from the phase 3 MELODY study found that the Beyfortus vaccine is 76.8% effective at preventing hospitalizations from RSV in the first five months of life, and 78.6% effective at reducing severe RSV associated lower respiratory infections within the same timeframe.

Monoclonal antibody immunizations are different from other vaccines. They rely on RSV antibodies grown in a lab, which are injected directly into the body. This allows for a faster rate of protection. By comparison, most other vaccines introduce an inactivated form of the virus into the body, prompting recipients to develop their own antibodies.

“This effective respiratory syncytial virus shot will be an important tool to prevent serious illness, hospitalizations, and deaths among infants, children as well as adults,” Maldonado said.

Risks and Side Effects

As with every treatment or vaccine, there are risks and possible side effects that can affect an infant after the administration of the Beyfortus vaccine.

Side effects localized to the injection site may include redness, pain, and swelling.

Systemic side effects up to seven days after injection may include:

While it is very rare, the most significant risks associated with Beyfortus include the possibility of developing gastroenteritis, bronchitis, or pneumonia.

When Will It Be Available to the Public?

Newborns and infants entering their first RSV season will be eligible, as well as children up to 24 months of age who are still vulnerable to severe RSV.

A Maternal Vaccine Is Now Available, Too

TheFDA has also approvedPfizer’s maternal RSV vaccine. The vaccine, called Abrysvo, will be administered to people who are pregnant during their third trimester in order to protect newborns. Abrysvo is already approved for adults age 60 and older.

FDA Greenlights a Second RSV Vaccine for Older Adults

The RSV prefusion F protein–based (RSVpreF) vaccine, which has shown 81% efficiency at reducing severe cases of lower respiratory tract illness within 90 days of birth, could prevent hundreds of infant deaths, as well as thousands of hospital stays.

“We thought long and hard about how to best protect newborns in a study with our vaccine candidate,” Pfizer’s Munjal said. “Newborns, of course, often cannot mount adequate immune defenses against infections, and direct immunization, or a vaccine given to the infant, is not always an option. But because protective antibodies are naturally passed from the mother to the newborn as early as the second trimester of pregnancy, we felt strongly that maternal immunization would be the best approach to offer the best level of protection.”

The vaccine is intended to be given to a mother between weeks 32–36 of pregnancy.

According to Keanna Ghazvini, a spokesperson for Pfizer, the RSVpreF vaccine for people who are pregnant will have major implications for the future of pediatric care and the overall burden associated with RSV.

“Up until this point, doctors still only have one option: using a ventilator for these severe cases,” Ghazvini told Verywell via email. “But what is important here is that we’ve found our vaccine works incredibly well in preventing severe cases through the first months of a child’s life.”

How Effective Is the Maternal Vaccine?

Results from the phase 3 Maternal Immunization Study for Safety and Efficacy (MATISSE) found that the RSVpreF vaccine is almost 82% effective at preventing severe complications from RSV in the first three months of life, while it is 69% effective through the child’s first six months.

Maternal vaccines are most effective when given between the second and third trimesters of pregnancy, allowing for the transfer of the RSV antibodies from the mother to the fetus via the placenta and later through breast milk. Infant protection from severe RSV illness will last for the first six months of life.

“This effective respiratory syncytial virus vaccine will be an important tool to prevent serious illness, hospitalizations, and deaths among infants, children as well as adults,” Maldonado said.

As with every vaccine, there are risks and possible side effects that can affect both mother and infant after the administration of the RSVpreF vaccine.

While very rare, adverse side effects can occur up to one month after vaccination.

The most significant risks associated with the RSVpreF vaccine include the possibility of a preterm birth and low birth weight.

When Will It Be Available?

Pfizer anticipates that this vaccine will be available in the fall, just in time for the next RSV season.

Correction - July 25, 2023: A previous version of this article referred to Beyfortus as a vaccine. It has been updated to clarify that it is an injectable drug designed to prevent RSV, and is considered an immunization.

7 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Muller WJ, Madhi SA, Seoane Nuñez B, et al.Nirsevimab for prevention of RSV in term and late-preterm infants.N Engl J Med. 2023;388(16):1533-1534. doi:10.1056/NEJMc2214773Centers for Disease Control and Prevention.RSV surveillance & research.Sanofi.Vaccines and monoclonal antibodies in immunization.Kampmann B, Madhi SA, Munjal I, et al.Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants.N Engl J Med. 2023;388(16):1451-1464. doi:10.1056/NEJMoa2216480Food and Drug Administration.Beyfortus (nirsevimab) for the prevention of RSV lower respiratory tract disease in infants and children.Sanofi.Press Release: FDA Advisory Committee unanimously recommends nirsevimab as first immunization against RSV disease for all infants.Centers for Disease Control and Prevention.Safety and efficacy of bivalent RSV prefusion F vaccine in vaccinated mothers and their infants.

7 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Muller WJ, Madhi SA, Seoane Nuñez B, et al.Nirsevimab for prevention of RSV in term and late-preterm infants.N Engl J Med. 2023;388(16):1533-1534. doi:10.1056/NEJMc2214773Centers for Disease Control and Prevention.RSV surveillance & research.Sanofi.Vaccines and monoclonal antibodies in immunization.Kampmann B, Madhi SA, Munjal I, et al.Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants.N Engl J Med. 2023;388(16):1451-1464. doi:10.1056/NEJMoa2216480Food and Drug Administration.Beyfortus (nirsevimab) for the prevention of RSV lower respiratory tract disease in infants and children.Sanofi.Press Release: FDA Advisory Committee unanimously recommends nirsevimab as first immunization against RSV disease for all infants.Centers for Disease Control and Prevention.Safety and efficacy of bivalent RSV prefusion F vaccine in vaccinated mothers and their infants.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Muller WJ, Madhi SA, Seoane Nuñez B, et al.Nirsevimab for prevention of RSV in term and late-preterm infants.N Engl J Med. 2023;388(16):1533-1534. doi:10.1056/NEJMc2214773Centers for Disease Control and Prevention.RSV surveillance & research.Sanofi.Vaccines and monoclonal antibodies in immunization.Kampmann B, Madhi SA, Munjal I, et al.Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants.N Engl J Med. 2023;388(16):1451-1464. doi:10.1056/NEJMoa2216480Food and Drug Administration.Beyfortus (nirsevimab) for the prevention of RSV lower respiratory tract disease in infants and children.Sanofi.Press Release: FDA Advisory Committee unanimously recommends nirsevimab as first immunization against RSV disease for all infants.Centers for Disease Control and Prevention.Safety and efficacy of bivalent RSV prefusion F vaccine in vaccinated mothers and their infants.

Muller WJ, Madhi SA, Seoane Nuñez B, et al.Nirsevimab for prevention of RSV in term and late-preterm infants.N Engl J Med. 2023;388(16):1533-1534. doi:10.1056/NEJMc2214773

Centers for Disease Control and Prevention.RSV surveillance & research.

Sanofi.Vaccines and monoclonal antibodies in immunization.

Kampmann B, Madhi SA, Munjal I, et al.Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants.N Engl J Med. 2023;388(16):1451-1464. doi:10.1056/NEJMoa2216480

Food and Drug Administration.Beyfortus (nirsevimab) for the prevention of RSV lower respiratory tract disease in infants and children.

Sanofi.Press Release: FDA Advisory Committee unanimously recommends nirsevimab as first immunization against RSV disease for all infants.

Centers for Disease Control and Prevention.Safety and efficacy of bivalent RSV prefusion F vaccine in vaccinated mothers and their infants.

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