The Food and Drug Administration (FDA) has approved the first vaccine for pregnant people to protect their infants from respiratory syncytial virus (RSV).
Pfizer’s RSVPreF (Abrysvo) was approved for use at 32-36 weeks’ gestation to protect infants from birth through 6 months. A Centers for Disease Control and Prevention (CDC) advisory committee is expected make recommendations for use of the vaccine at an upcoming meeting, which would be followed by a decision from the CDC director. Guidance likely will include how it will be used in relation to the monoclonal antibody nirsevimab, which recently was approved for use in infants and high-risk toddlers to protect them from RSV.
“RSV is a common cause of illness in children, and infants are among those at highest risk for severe disease, which can lead to hospitalization,” Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research, said in a press release Monday. “This approval provides an option for healthcare providers and pregnant individuals to protect infants from this potentially life-threatening disease.”
RSV is the leading cause of infant hospitalization in the U.S. There are about 58,000 to 80,000 hospitalizations and 100 to 300 deaths per year in children under 5 years, according to CDC data.
In May, an FDA advisory committee supported use of RSVPreF, which is made up of RSV recombinant stabilized prefusion F proteins. All 14 voting members agreed data are adequate to support efficacy of the vaccine, while 10 felt the safety data are adequate.
Clinical trial data in women who received the vaccine at 32-36 weeks showed that at 90 days it reduced the risk of medically attended lower respiratory tract disease by 35% (although confidence intervals went below 0) and severe disease by 91% compared to placebo. At six months after birth, the reductions were 57% and 77% respectively.
The most common side effects among pregnant individuals were pain at the injection site, headache, muscle pain and nausea. About 2.6% of those receiving the vaccine reported a fever.
The main safety concern for infants is preterm birth. The study found a preterm birth rate of 5.7% in the vaccine group compared to 4.7% in the placebo group. Pfizer representatives said these differences were driven largely by data from South Africa and are not statistically significant.
Some FDA advisers found the findings concerning while others said the benefits outweigh the risks. The FDA will require a warning about the potential for preterm births in the prescribing information and recommend giving it no earlier than 32 weeks’ gestation.
Approval of RSVPreF comes just weeks after the CDC director signed off on nirsevimab (Beyfortus), a monoclonal antibody given to infants and high-risk toddlers to protect them from RSV. Health officials previously indicated children likely would not need protection from both nirsevimab and a maternal vaccine, but those recommendations have not been finalized.
CDC experts discussing the two products in June said the maternal vaccine may be more resilient to mutations, lower in price and provide protection at birth. However, the protection likely wanes more quickly than nirsevimab. Some infants may not get full protection from maternal vaccination if they were born too soon after immunization, born prematurely or due to maternal disease. Maternal uptake of flu and tetanus, diphtheria and pertussis (Tdap) vaccines tends to be lower than routine childhood vaccines, and it’s unclear if pregnant people would accept multiple vaccines. There also are outstanding questions about whether RSVpreF would interfere with the effectiveness of Tdap if given together.
Nirsevimab, a monoclonal antibody considered to be a passive immunization, could have the benefit of being given just as infants are entering RSV season. However, it has its own barriers to implementation including the significant cost, uncertain payment in hospital settings, historical lags in insurance payments and inadequate Current Procedural Terminology therapeutic administration codes that do not cover counseling.
The AAP is continuing to discuss these issues with federal officials and advocate for a comprehensive strategy to ensure equitable access to the drug. A typical RSV season begins in October. Given the many barriers to implementation of nirsvimab, the AAP continues to recommend the use of palivizumab as RSV prophylaxis for high-risk infants unable to access nirsevimab this 23-’24 RSV season.