Respiratory syncytial virus (RSV) is a common and potentially severe respiratory pathogen in older adults. We previously found the vaccine to be effective at preventing infections, ED visits, and hospitalizations in the season it was administered.1 However, limited data are available on longer-term protection, particularly beyond one year after vaccination.
To further understand RSV vaccine effectiveness in older adults, we studied 1,204,649 patients aged 60 and older who had an RSV lab test during the 2024/2025 RSV season. Patients were matched based on the month of their RSV lab test, age, and factors that indicate increased risk of complications from an RSV infection. Patients were grouped based on the time elapsed between RSV vaccination and RSV lab testing.
During the 2024/2025 RSV season, patients vaccinated two weeks to six months prior had a positive RSV infection rate of 1.1%, while those vaccinated more than a year prior had rates more than twice as high and those who have never received the RSV vaccine had rates nearly four times as high. Similar patterns were observed for ED visits and hospitalizations, as seen in Figure 1.
Vaccine effectiveness (VE) declined steadily over time. For RSV infection, VE was 71% at 4 months, decreasing to 40% by month 19. Effectiveness against RSV-related ED visits followed a similar pattern, dropping from 71% in month 4 to 46% by month 19. Hospitalization protection declined from 73% to 44% over the same period.
These findings suggest that while protection against severe outcomes persists into the next season, it is significantly reduced compared to the initial vaccination season.
