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RSV Disease Severity Comparable to Unvaccinated COVID-19, Influenza: New Research
In adults hospitalized with RSV, odds of severe outcomes, including death, were much higher than for those admitted for, but vaccinated against, COVID-19, flu.
Adults hospitalized for infection with respiratory syncytial virus (RSV) experienced disease severity similar to that seen in unvaccinated adults with influenza or COVID-19 and more severe than COVID-19 and influenza among vaccinated persons with each disease for the critical outcomes of ICU admission and IMV or death.
The findings are based on data for adults hospitalized in 20 states during the 16 months before the first RSV vaccine became available and recommended for adults aged 60 years and older based on a shared decision-making conversation with their health care professional.
Study authors from the Investigating Respiratory Viruses in the Acutely Ill (IVY) Network note that although the frequency of hospitalizations for RSV during the lead-up to vaccine availability was lower than for either flu or COVID-19, the most severe outcomes were comparable, suggesting a powerful message to be included in public health messaging for RSV vaccination as the US policy continues to evolve. The high disease severity observed among older adults without previous RSV vaccination in this analysis is important to guide decision-making for RSV vaccination in this population.
For the prospective cohort study, Diya Surie, MD, from the U.S. Centers for Disease Control and Prevention, and colleagues enrolled individuals aged 18 years and older admitted to any of the 25 hospitals in 20 states participating in the IVY network with a laboratory confirmed diagnosis of RSV, SARS-CoV-2, or influenza between February 1, 2022, and May 31, 2023. Data analysis took place from August to October 2023.
Researchers compared the severity RSV disease with COVID-19 and influenza severity, stratified by COVID-19 and flu vaccination status, for clinical outcomes that included the composite of invasive mechanical ventilation (IMV) and in-hospital death, according to the study.
The final cohort numbered 7998 with 6.1% (484) hospitalized with RSV, 80% (6422) with COVID-19, and 13.7% (1092) with influenza. Surie and colleagues noted that hospitalizations for COVID-19 occurred throughout the study period while peaking for flu and RSV between November and December 2022.
FINDINGS
According to the study results, among those hospitalized with RSV, 12% required IMV or died compared with 14.1% of unvaccinated individuals with COVID-19 and 9.2% of vaccinated persons with COVID-19.
Among participants with influenza, IMV or death occurred in 10.3% of those unvaccinated against the virus and among 5.1% of those who were vaccinated.
The adjusted odds of IMV or in-hospital death did not differ significantly among individuals admitted for RSV and those unvaccinated with COVID-19 (aOR, 0.82; 95% CI, 0.59-1.13; P = .22) or unvaccinated with influenza (aOR, 1.20; 95% CI, 0.82-1.76; P = .35). However, the researchers found the odds of IMV or death were significantly elevated among individuals hospitalized with RSV when compared with vaccinated adults with COVID-19 (aOR, 1.38; 95% CI, 1.02-1.86; P = .03) or with flu (aOR, 2.81; 95% CI, 1.62-4.86; P < .001).
Surie et al found that adults hospitalized with RSV were younger than those hospitalized with COVID-19 (65 vs 68 years) and of similar age to those with influenza. Among those hospitalized with RSV, a larger proportion identified as non-Hispanic Black compared with those admitted for COVID-19 (23.8% vs 19.4%) but the percentage was similar among those with influenza. Underlying immunocompromising conditions were similarly distributed among those with RSV (20.5%) and COVID-19 17.7%) but were more prevalent in those with RSV vs influenza (13.6%). Chronic cardiovascular and pulmonary conditions were common across all 3 infections.
Among limitations to the study the authors point out that RSV may have been preferentially detected among more severely ill persons who were more likely to be tested and thus enrolled. They also state that analyses did not consider treatment with antiviral or immunomodulatory medications. They acknowledge, too, the difficulty in quantifying treatment effect on disease severity and accounting for that in comparisons that were made.
The study’s contribution to current understanding of RSV severity in the context of cocirculating respiratory infections and the comparative impact of vaccination is valid, authors state. Moreover, the significant severity of RSV observed in unvaccinated older adults is ”important to guide decision-making for RSV vaccination in this population.”
While Surie et al call for additional research to evaluate the protection offered by the vaccines against severe respiratory disease, “our results suggest that there is a burden of disease beyond prevention of RSV hospitalization—the reduction of in-hospital RSV disease severity—that could occur with RSV vaccination, as shown for COVID-19 and influenza vaccination in both previous studies and this analysis,” they concluded.
