A study yesterday in Influenza and Other Respiratory Viruses shows that, in the year before rollout of the respiratory syncytial virus (RSV) vaccine, hospitalization rates among US adults 60 and older were 10 to 17 times the rate of younger adults.

RSV vaccines were first authorized for use in the United States in the summer of 2024 for adults 60 and up. Prior to that, a significant proportion of older Americans were at risk every year from severe respiratory infections from the virus, but the exact burden of RSV was hard to estimate in the seasons following the 2020 COVID-19 pandemic, as RSV transmission patterns were altered in the wake of non-pharmaceutical pandemic interventions.

“Ascertaining the impact of the RSV adult vaccination program is of public health interest and requires contemporary assessments of RSV burden preceding vaccine introduction,” the authors wrote.

The study considered all RSV-related hospitalizations at the Vanderbilt University Medical Center from October 1, 2022, through September 30, 2023. RSV was detected per nasal swabbing upon hospital admission, per COVID-19 guidelines.

The 1-year testing period saw 21,392 hospitalizations, and RSV testing was completed for 9,958 (46.6%) of them. RSV was detected in 49 patients.

Hospital rates increased with age

The authors said that after accounting for the untested population and the surveillance hospital market share, the annual incidence rate of RSV-associated hospitalization was 31.5 (95% confidence interval [CI], 21.9 to 44.0) per 100,000 adults.

Rates were 10-fold and 17-fold higher among adults aged 60–74 years and ≥ 75 years compared with adults 18–49 years old

“Rates were 10-fold and 17-fold higher among adults aged 60–74 years and ≥ 75 years compared with adults 18–49 years old,” the authors noted.

The authors said the findings support RSV vaccination of older Americans. When compared with the burden of other vaccine-preventable respiratory diseases for the same study period, the number of flu-associated US adult hospitalizations was approximately 322,700, the authors wrote, and the estimated number of US adult hospitalizations for pneumococcal pneumonia ranged from 111,000 to 226,000, according to recent estimates.

“In the year preceding the introduction of RSV vaccination in the United States, RSV was associated with a substantial burden of adult hospitalizations, especially among adults ≥ 60 years old, underscoring the potential benefits of RSV vaccination in older adults,” the authors concluded.