Pfizer’s RSV vaccine was 90% effective at preventing the most severe outcomes in the first-ever vaccination season, the company said, underscoring its potential benefits as another respiratory virus season kicks off.
The new data, presented at IDWeek Thursday, are a clearer look at how Abrysvo fared at preventing severe illness and hospitalizations. The results come from Kaiser Permanente of Southern California, though the trial was paid for by Pfizer and includes Pfizer co-authors.
The retrospective study looked at patients 60 and older who were hospitalized or came to the emergency room with severe acute respiratory illness. In that group, the vaccine was 90% effective at preventing the most severe respiratory cases, with only one positive case identified among patients vaccinated with Abrysvo. The confidence interval was wide, stretching from 24% to 99% in the primary analysis.
While the results aren’t vastly different from what the company has shown in previous trials, the study was the first time immunocompromised people were reviewed, after those patients weren’t included in the Phase 3 study.
Despite the introduction of RSV vaccines for the first time, rates of RSV-associated hospitalization among people 65 and older last fall and winter were the highest recorded in the last seven years.
According to data from the CDC, the hospitalization rate in that age group peaked at 9.4 hospitalizations per 100,000 people in the last week of December 2023. The second-highest weekly hospitalization peak in the last seven years was 6.1 per 100,000 people during the 2022-2023 season, as people came out of Covid-19 precautions and the prevalence of other respiratory illnesses surged.
Public health officials shifted their RSV vaccination strategy over the summer, moving from advising that anyone 60 and older consult a healthcare professional before getting a shot to outright recommending one for people in the same age group who are at higher risk of severe disease. Advisors to the CDC also specified that anyone 75 and older should get the vaccine. Roughly 1-in-4 people 60 and older got vaccinated in the first season.
But because the previous guidance technically included anyone 60 and older, investors and analysts projected that the new guidance may actually shrink the market. Clinicians and pharmacists, however, felt that the new guidance would be easier to implement and that they could more confidently advise who should get the shot.
Recent data assessed by Jefferies at the beginning of October found a 40% drop in vaccine prescriptions compared to the same point in 2023. But there were signs of hope, with both GSK and Pfizer notching double-digit gains in prescriptions in the last week of September compared to the week prior. Prescriptions of Moderna’s vaccine, mRESVIA, were also growing week-to-week, but those gains were “incremental,” according to Jefferies.