Update on seasonal flu, RSV infections, and vaccines


Chest Infections & Disaster Response Network

Chest Infections Section

November 12 marks World Pneumonia Day, and while it has long been recognized that viruses play a significant role in causing pneumonia, awareness has surged due to the COVID-19 pandemic. Furthermore, with the advent of rapid molecular diagnostics, the contribution of respiratory viral pathogens in pneumonia has become clearer (Seema J, et al. N Engl J Med. 2015 Jul 30;373[5]:415-27). Despite COVID-19 remaining a substantial threat, infection rates with other respiratory viruses are on the rise and will continue to increase during colder months. Here, we will provide an update on influenza and RSV:

Currently, influenza activity in the United States is low (National Center for Immunization and Respiratory Diseases. FluView. 2023 Oct 4. Vaccination coverage for US adults during the previous influenza season stood at 47% (Centers for Disease Control and Prevention. FluVaxView Vaccination Dashboard. 2023 Oct 4. Hospitalizations were estimated to range between 300,000 and 650,000, a significant increase from the 2021-2022 season, which saw about 100,000 hospitalizations (Centers for Disease Control and Prevention. Preliminary In-Season Estimates of Influenza Burden. 2023 Oct 4. Data from the Southern Hemisphere’s recent influenza season indicates a 52% vaccine efficacy in preventing influenza-associated hospitalizations (Fowlkes AL, et al. MMWR Morb Mortal Wkly Rep. 2023 Sep 15;72[37]:1010-5). Influenza hospitalization rates are likely returning to higher pre-COVID-19 levels.

Respiratory Syncytial Virus (RSV) is a seasonal pathogen causing substantial morbidity and mortality. This year, two new vaccines have become available to prevent RSV-associated lower respiratory tract diseases, boasting a vaccine effectiveness of over 80% for the first and over 70% for the second season post-administration (Melgar M, et al. MMWR Morb Mortal Wkly Rep. 2023 Jul 21;72[29]:793-801). The CDC’s Advisory Committee on Immunization Practices recommends a single dose for adults over 60, and one vaccine is FDA-approved for pregnant individuals (32-36 weeks gestation) to provide passive infant immunity.

In summary, both the current influenza vaccine and the new RSV vaccines demonstrate effectiveness and are strongly recommended, alongside an updated COVID-19 vaccine.

John Huston, MD

Jamie Felzer, MD, MPH – Section Fellow-in-Training

Charles Dela Cruz, MD – Section Member-at-Large

Sebastian Kurz, MD, FCCP – Network Member-at-Large

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