Pfizer RSV vaccine protects for more than 2 seasons in older adults: Research

Pfizer announced Thursday that its vaccine for RSV, or respiratory syncytial virus, protects older adults for more than two seasons, according to a late-stage clinical trial.

Pfizer announced that its Abrysvo vaccine “maintained consistently high protective efficacy” throughout two seasons in older adults after receiving one dose. One dose of Abrysvo was 77.8 percent effective against lower respiratory tract disease associated with RSV following the second season, according to Pfizer.

This was slightly lower than the efficacy observed at the end of the first season, when one shot of the vaccine was found to be 89.9 percent effective.

“We are encouraged by the level of protection that we observed after two full RSV seasons for ABRYSVO,” Annaliesa Anderson, Pfizer’s senior vice president and chief scientific officer for vaccine research and development, said. “This new data indicates that broad and durable protection against both types of RSV that cause disease, RSV A and RSV B, is the potential benefit to having a bivalent vaccine.”

The U.S. Food and Drug Administration (FDA) approved Pfizer’s Abrysvo vaccine to prevent the respiratory disease RSV in older adults in May 2023, becoming the second RSV shot approved for use in the U.S. for older adults. The Centers for Disease Control and Prevention (CDC) later recommended its use for older adults in June.

The vaccine’s effectiveness against a less severe form of the lower respiratory tract disease associated with RSV was about 55.7 percent after the second season. This is a drop from the 65.1 percent effectiveness Pfizer said it had after the first season.

Pfizer also noted that there was no new adverse events reported after the end of the second season “beyond what was reported by subjects in the clinical trial during the first season.”

The FDA also approved Abrysvo to prevent RSV in infants last year, through a dose administered to pregnant mothers during their third trimester. The CDC approved its use in pregnant women during weeks 32 through 36 of gestation.