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Interim Effectiveness Estimates of 2024 Southern Hemisphere Influenza Vaccines in Preventing Influenza-Associated Hospitalization — REVELAC-i Network, Five South American Countries, March–July 2024

2024; Centers for Disease Control and Prevention; Volume: 73; Issue: 39 Linguagem: Inglês

10.15585/mmwr.mm7339a1

1545-861X

Erica E. Zeno, Francisco Nogareda, Annette K. Regan, Paula Couto, Marc Rondy, Jorge Jara, Carla Voto, María Paz Rojas Mena, Nathalia Katz, María Del Valle Juárez, Estefanía Benedetti, Francisco José de Paula Júnior, Walquiria Aparecida Ferreira da Almeida, Carlos Edson Hott, Paula Rodríguez Ferrari, Natalia Vergara Mallegas, Marcela Avendaño Vigueras, Chavely Domínguez, Marta Von Horoch, Cynthia Vázquez, Eduardo Silvera, Héctor Chiparelli, Natalia Goñi, Laura Castro, Perrine Marcenac, Rebecca Kondor, Juliana Almeida Leite, Martha Velandia-González, Eduardo Azziz‐Baumgartner, Ashley Fowlkes, Daniel Salas, Estefanía Benedetti, Andrea Pontoriero, María Del Valle Juárez, Nathalia Katz, María Paz Rojas Mena, Carla Voto, Walquiria Aparecida Ferreira da Almeida, Daiana Araújo da Silva, Francisco José de Paula Júnior, Felipe Cotrim de Carvalho, Ana Catarina de Melo Araújo, Greice Madeleine Ikeda do Carmo, Carlos Edson Hott, Miriam Teresinha Furlam Prando Livorati, Marcela Avendaño, María Fernanda Olivares Barraza, Patricia Bustos, Paula Rodríguez Ferrari, Natalia Vergara Mallegas, Rodrigo Fasce Pineda, Silvia Battaglia, Marta Von Horoch, Chavely Domínguez, Maria José Ortega, Elena Penayo, Cynthia Vázquez, Héctor Chiparelli, Natalia Goñi, Karina Griot, Jose Eduardo Silvera, Daiana Tritten, Steven Tapia Villacís,

Respiratory viral infections research

To reduce influenza-associated morbidity and mortality, countries in South America recommend annual influenza vaccination for persons at high risk for severe influenza illness, including young children, persons with preexisting health conditions, and older adults. Interim estimates of influenza vaccine effectiveness (VE) from Southern Hemisphere countries can provide early information about the protective effects of vaccination and help guide Northern Hemisphere countries in advance of their season. Using data from a multicountry network, investigators estimated interim VE against influenza-associated severe acute respiratory illness (SARI) hospitalization using a test-negative case-control design. During March 13-July 19, 2024, Argentina, Brazil, Chile, Paraguay, and Uruguay identified 11,751 influenza-associated SARI cases; on average, 21.3% of patients were vaccinated against influenza, and the adjusted VE against hospitalization was 34.5%. The adjusted VE against the predominating subtype A(H3N2) was 36.5% and against A(H1N1)pdm09 was 37.1%. These interim VE estimates suggest that although the proportion of hospitalized patients who were vaccinated was modest, vaccination with the Southern Hemisphere influenza vaccine significantly lowered the risk for hospitalization. Northern Hemisphere countries should, therefore, anticipate the need for robust influenza vaccination campaigns and early antiviral treatment to achieve optimal protection against influenza-associated complications.