RSV's Seasonal Comeback: Tracking the Return of RSV

Respiratory syncytial virus (RSV) has long been a seasonal concern in the US, causing epidemics of respiratory illness primarily during the fall and winter. However, the COVID-19 pandemic disrupted the typical patterns of RSV transmission, leading to an unusual hiatus in RSV circulation. As of the 2022 and 2023 fall and winter seasons, there were signs of a gradual return to the pre-pandemic seasonality of RSV, indicating the resumption of its seasonal epidemics, according to a report published in MMMR.

Each year, RSV causes significant morbidity and mortality among adults, leading to lower respiratory tract disease (LRTD), hospitalizations, and even death. Estimations vary due to underreporting and limited diagnostic sensitivity in adults, but it is estimated that between 60,000 and 160,000 hospitalizations and 6,000 to 10,000 deaths occur annually among adults aged 65 and older. Certain medical conditions, including chronic obstructive pulmonary disease, heart diseases, diabetes, and immunocompromised states, elevate the risk of RSV-associated hospitalization. Long-term care facility residents and compromised elderly patients are particularly susceptible to severe RSV illness.

In May 2023, the Food and Drug Administration (FDA) approved the first vaccines designed to prevent RSV-associated LRTD in adults aged 60 and older. These vaccines, RSVPreF3 (Arexvy, GSK) and RSVpreF (Abrysvo, Pfizer), represent a significant development in combating RSV in this vulnerable demographic.

To assess the safety and efficacy of these vaccines, the CDC's Advisory Committee on Immunization Practices (ACIP) established the RSV Vaccines Adult Work Group, which systematically reviewed available evidence. Both vaccines demonstrated moderate to high efficacy in preventing symptomatic RSV-associated LRTD over two consecutive RSV seasons, with RSVPreF3 showing 74.5% efficacy and RSVpreF showing 84.4% efficacy. However, trials were not powered to estimate effectiveness against hospitalization or death.

As a result of these findings, on June 21, 2023, ACIP recommended that adults aged 60 and older may receive a single dose of RSV vaccine through shared clinical decision-making. This approach allows health care providers and patients to make vaccination decisions based on individual risk factors, preferences, and medical history. Those at the highest risk for severe RSV disease, including individuals with certain chronic medical conditions, compromised immunity, or advanced age, are more likely to benefit from vaccination.

Coadministration of RSV vaccines with other adult vaccines is considered acceptable, although data on immunogenicity and reactogenicity are currently limited. Providers should weigh the benefits and risks of coadministering RSV vaccines with other recommended vaccines based on patient characteristics and preferences.

"When deciding whether to coadminister other vaccines with an RSV vaccine, providers should consider whether the patient is up to date with currently recommended vaccines, the feasibility of the patient returning for additional vaccine doses, risk for acquiring vaccine-preventable disease, vaccine reactogenicity profiles, and patient preferences. Postlicensure efficacy and safety monitoring of coadministered RSV vaccines with other vaccines will further direct guidance," according to coauthors.

Reference

Melgar M, Britton A, Roper, LE, et al. Use of respiratory syncytial virus vaccines in older adults: recommendations of the advisory committee on immunization practices — United States, 2023. MMWR Morbidity and Mortality Weekly Report. 2023;72. doi:10.15585/mmwr.mm7229a4