Pfizer's RSV vaccine 90% effective against severe respiratory disease

Pfizer has announced that its RSV vaccine, Abrysvo, has demonstrated 90% effectiveness in averting severe outcomes during its inaugural vaccination season. This highlights the vaccine's significant potential as the respiratory virus season begins. The updated data, shared at IDWeek, offer a comprehensive view of Abrysvo's performance in preventing severe illnesses and hospitalizations. The study was conducted by Kaiser Permanente of Southern California, although Pfizer funded the trial and included Pfizer co-authors among the researchers.

The study was retrospective, focusing on patients aged 60 and above who were either hospitalized or visited the emergency room due to severe acute respiratory illness. In this specific group, the vaccine was found to be 90% effective in preventing the most severe respiratory cases, with only one positive case reported among those vaccinated with Abrysvo. However, the confidence interval was broad, ranging from 24% to 99% in the primary analysis.

While these findings are consistent with previous results presented by Pfizer, this study is noteworthy as it is the first to include immunocompromised individuals, a group that was not part of the Phase 3 trials. Despite the introduction of RSV vaccines, the rates of RSV-associated hospitalizations among people aged 65 and older reached their highest levels in the past seven years during the last fall and winter seasons.

Data from the CDC indicated that the hospitalization rate for this age group peaked at 9.4 hospitalizations per 100,000 individuals in the final week of December 2023. This was significantly higher than the second-highest peak of 6.1 per 100,000 people during the 2022-2023 season, a period marked by a resurgence of respiratory illnesses as COVID-19 precautions were lifted.

In response to these high hospitalization rates, public health officials revised their RSV vaccination strategy over the summer. Initially, the guidance recommended that individuals aged 60 and older consult healthcare professionals before getting vaccinated. However, the new strategy directly recommends vaccination for those in the same age group who are at higher risk of severe disease. Additionally, CDC advisors specifically recommended the vaccine for everyone aged 75 and older. During the first vaccination season, approximately one in four individuals aged 60 and above received the shot.

There was some concern among investors and analysts that the new guidance, which narrows the target population, might reduce the market size. However, healthcare providers and pharmacists believed that the updated guidance would be easier to implement and would allow them to more confidently advise patients on getting the vaccine.

Recent data from Jefferies at the beginning of October showed a 40% decline in vaccine prescriptions compared to the same period in 2023. Despite this, there were encouraging signs, with both GSK and Pfizer recording double-digit increases in prescriptions in the last week of September compared to the previous week. Moderna's vaccine, mResvia, also saw a week-to-week increase in prescriptions, although these gains were described as incremental by Jefferies.