Pfizer's Abrysvo Vaccine Demonstrates Strong Efficacy Against RSV in Adults

This article first appeared on our sister site, Infection Control Today.

Pfizer has unveiled results from its phase 3 clinical trial of the Abrysvo vaccine, showcasing robust efficacy against RSV in adults aged 60 and older. these insights offer valuable perspectives on RSV prevention strategies and the evolving landscape of vaccine development.

“Pfizer has announced efficacy and safety data on their new RSV vaccine, Abrysvo, effective in older adults and infants, two vulnerable populations,” said Sharon Ward-Fore, MS, BS, MT(ASCP), CIC, FAPIC.

“RSV causes between 60,000 to 160,000 hospitalizations and up to 13,000 deaths in people over 60 years old. This vaccine is bivalent, so effective against all RSV lower respiratory tract subgroups. This is good news and another vaccine in our prevention arsenal.”

The phase 3 trial, known as RENOIR (RSV vaccine Efficacy study iN Older adults Immunized against RSV disease), revealed a notable vaccine efficacy of 77.8% (95.0% CI: 51.4, 91.1) against RSV-associated lower respiratory tract disease (LRTD) with 3 or more symptoms after the second season. This follows an initial vaccine efficacy of 88.9% (95.0% CI: 53.6%, 98.7%) after the first season, indicating durable protection against RSV.

Furthermore, the data showed consistent efficacy against both RSV A and RSV B subtypes, with vaccine efficacy rates of greater than or equal to 80% for LRTD with 3 or more symptoms. Even against less severe LRTD, defined by 2 or more symptoms, the vaccine-maintained efficacy from 65.1% (95.0% CI: 35.9%, 82.0%) after the first season to 55.7% (95.0% CI: 34.7%, 70.4%) after the second season. Overall, the vaccine demonstrated an efficacy of 81.5% (95.0% CI: 63.3, 91.6) against RSV-associated LRTD with 3 or more symptoms across both seasons.

Importantly, the safety profile of Abrysvo remained favorable, with no new adverse events reported beyond those observed in the first RSV season. These findings provide crucial data for infection preventionists and epidemiologists as they evaluate the potential role of Abrysvo in their RSV prevention strategies.

Annaliesa Anderson, PhD, senior vice president and chief scientific officer of Vaccine Research and Development at Pfizer, expressed optimism about the results in the press release, stating, “We are encouraged by the level of protection that we observed after 2 full RSV seasons for Abrysvo. This data underscores the potential benefit of a bivalent vaccine offering broad and durable protection against both RSV A and RSV B.”

Abrysvo received FDA approval in May 2023 for the prevention of LRTD caused by RSV in individuals aged 60 and older. It was also approved for maternal immunization to protect infants from birth up to 6 months of age. These regulatory milestones, coupled with the strong efficacy data, highlight the potential of Abrysvo in preventing RSV-related morbidity and mortality.

The vaccine is indicated for the prevention of LRTD caused by RSV in people aged 60 years and older, as well as for pregnant individuals at 32 through 36 weeks gestational age to prevent LRTD and severe LRTD caused by RSV in infants from birth through 6 months of age.

Pfizer intends to submit these data to regulatory authorities and vaccine technical committees, paving the way for further discussions on the vaccine's role in RSV prevention strategies.