Flu Vaccine Efficacy Examined in Southern Hemisphere Countries

MONDAY, Oct. 7, 2024 (HealthDay News) -- Based on data from Southern Hemisphere countries, a low proportion of patients with influenza-associated severe acute respiratory illness (SARI) were vaccinated against influenza, according to research published in the Oct. 3 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Erica E. Zeno, Ph.D., from the CDC in Atlanta, and colleagues conducted interim estimates of influenza vaccine effectiveness (VE) from Southern Hemisphere countries, which can help guide Northern Hemisphere countries in advance of their season. Interim VE against influenza-associated SARI hospitalization was estimated using data from a multicountry network.

The researchers identified 11,751 influenza-associated SARI cases during March 13 to July 19, 2024, in Argentina, Brazil, Chile, Paraguay, and Uruguay. On average, 21.3 percent of these patients were vaccinated against influenza, with an adjusted VE of 34.5 percent against hospitalization. The adjusted VE was 36.5 percent against the predominating subtype A(H3N2) and was 37.1 percent against A(H1N1)pdm09.

"These data suggest that influenza vaccine demand was still low post-COVID-19 but that vaccination prevented approximately one-third of influenza-associated hospitalizations among groups at high risk for influenza-associated complications," the authors write. "These findings support [the U.S. Centers for Disease Control and Prevention and World Health Organization's] recommendation that all eligible persons aged ≥6 months should receive influenza vaccination."

One author disclosed participating on a data safety monitoring board for Moderna's candidate mRNA respiratory syncytial virus vaccine for pregnant women.

Abstract/Full Text