Pediatrician Capt. Michael Zimmerman, with the help of Kaylin Bowers, a registered nurse, assesses a five-month-old infant for RSV. Federal regulators on Monday approved a maternal RSV vaccine administered during pregnancy to protect infants from severe illness. (Kelly Acevedo/U.S. Army)
Federal regulators on Monday approved a maternal RSV vaccine administered during pregnancy to protect infants from severe illness.
It’s the latest in a new arsenal of immunizations against the common respiratory virus that is the leading cause of hospitalization in young children and kills thousands of seniors annually.
For decades, public health officials had few defenses against respiratory syncytial virus, which infects nearly every child before their second birthday. Infants are especially vulnerable because they have smaller airways, as are toddlers with asthma and other conditions that place them at high risk.
A double-blind study of more than 7,000 women around the world found Pfizer’s vaccine administered in the third trimester of pregnancy to be effective in preventing severe illness requiring medical attention. It was 82 percent effective at protecting infants from severe illness during the three months after birth, and waned to 69 percent effective over six months. The study found no major safety concerns.
A reduction in overall medical visits for RSV, including mild cases, did not reach statistical significance to demonstrate effectiveness. The peer-reviewed research funded by Pfizer was published in the New England Journal of Medicine in April.
“This approval provides an option for healthcare providers and pregnant individuals to protect infants from this potentially life-threatening disease,” Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a statement.
It’s unclear whether the maternal RSV vaccine, Abrysvo, would be available in time to protect infants born during the upcoming RSV season, which usually starts in fall and peaks in winter. The vaccine needs to be recommended by the Centers for Disease Control and Prevention before the shots are administered. The committee that advises the CDC on vaccine recommendations is expected to meet again in mid-September and could potentially consider the RSV vaccine then.
But there’s another way to protect young children in the interim. Earlier this month, regulators approved the monoclonal antibody treatment Beyfortus given directly to infants and high-risk toddlers to prevent severe RSV illness. The treatment essentially acts as a vaccine by preventing severe RSV cases for five months, enough for one RSV season.
The maternal vaccine, in contrast, works by passing antibodies down to infants during pregnancy, providing an immediate but temporary shield. Vaccines for influenza, diphtheria, tetanus and pertussis are also given as maternal immunizations.
In approving the RSV maternal vaccine, the FDA said the most common side effects reported in trials were pain at the injection site, headache, muscle pain and nausea.
The agency also noted a slightly higher percentage of Abrysvo recipients experienced pre-term births (5.7 percent) compared with placebo recipients (4.7 percent). It was unclear whether the vaccine caused the imbalance, but providers are advised to avoid the risk of pre-term birth by administering the vaccine between weeks 32 and 36 of gestation.
Infants born to Abrysvo recipients also had higher rates of low birth weight and jaundice compared to those born to women given the placebo.
The CDC estimates RSV causes 58,000 to 80,000 annual hospitalizations and 100 to 300 deaths of children younger than 5 years old.
An unusual surge in RSV cases last year overwhelmed some children’s hospitals and pediatric offices. Experts and health officials say it may have been an anomaly triggered by the coronavirus pandemic. Among the theories: Toddlers who were not exposed as infants because of social distancing and masking may have been more susceptible, and children who contracted mild or asymptomatic covid-19 cases may have had weaker immune systems.
Abrysvo, Pfizer’s vaccine now approved for pregnancy, and another RSV vaccine manufactured by GSK have recently been approved for adults age 60 and older. The CDC recommends people in that age group ask their doctors whether they should get vaccinated and receive the shot as soon as possible, which is already available at major retail pharmacies in most states.
In seniors, RSV causes 60,000 to 160,000 hospitalizations and 6,000 to 10,000 deaths every year. Those with health problems like heart or lung disease or declining immune systems are at higher risk for severe RSV disease.
Carolyn Y. Johnson contributed to this report.
