RSV is a leading cause of lower respiratory tract disease (LRTD) with severe outcomes, particularly among older adults and those with compromised immune systems. The Centers for Disease Control and Prevention estimates that RSV contributes to around 60,000 to 160,000 hospitalizations and 6,000 to 10,000 deaths among older adults in the United States each year.
Protection may persist into third season
For the study that looked at RSV vaccine protection over the course of three seasons, researchers led by a team from Kaiser Permanente Southern California and Pfizer analyzed data from 3,131 hospital and ED visits for LRTD and 4,797 for acute respiratory illness (ARI) among adults aged 60 and older. Roughly 71% of the LRTD visits and 57% of the ARI visits resulted in hospitalization.
After adjusting for differences between the groups, the researchers estimated that vaccination was 80% effective against RSV-related LRTD requiring hospitalization or ED care in the first season after vaccination and 70% in the second. The estimate fell to 51% in the third season, but the 95% confidence interval (CI) was wide due to a limited number of events and ranged as low as -12%, meaning the study couldn’t establish protection against hospitalization or ED care in year three.
The RSV vaccine’s estimated effectiveness against ARI-related hospitalization and ED care was 81% in the first year, 64% in the second year, and 60% (95% CI, 15% to 81%) in the third year. The confidence interval for third-season ARI vaccination effectiveness was slightly narrower and stayed above zero, suggesting that the vaccine offered protection in the third year.
“Additional studies and analyses are needed to further define durability of protection in specific population subgroups,” write the researchers.
But overall, they conclude, “Bivalent RSVpreF provides protection against RSV-related respiratory disease hospitalization/ED visits for at least three seasons after vaccination, resulting in substantial individual and public health benefit.”
Vaccines cut hospitalization rates by 82%
For the study that estimated vaccine effectiveness (VE) during the 2023-24 respiratory virus season, researchers from the Food and Drug Administration analyzed data from more than 14.5 million US adults aged 65 years and older to assess the how well both the RSVPreF3+AS01 (an adjuvanted vaccine, Arexvy, made by GSK) and RSVpreF protected against hospitalization and death.
Among the participants, the median age was 74 years, and roughly 58% were women. Approximately 14% received RSVPreF3+AS01, and around 6% received an RSVpreF vaccine.
Overall, the researchers estimated that VE against RSV-related hospitalization was nearly 82% and was 85% against RSV death. For immunocompromised participants, VE against RSV hospitalization was approximately 72%.
RSV vaccines provided substantial protection to immunocompromised people.
“The large study size allowed us to granularly assess risk against RSV-related hospitalization by age, finding no evidence of effect modification by age, including for beneficiaries aged 85 years or older,” write the researchers. “The large study size also allowed us to assess effectiveness by more granular immunocompromised subcategories. RSV vaccines provided substantial protection to immunocompromised individuals.”
The authors conclude that “the RSVPreF3+AS01 and RSVpreF RSV vaccines had high estimated effectiveness against RSV-related hospitalization and death” in adults aged 65 and older, including immunocompromised people