Influenza vaccine effectiveness against hospitalizations in children and older adults—Data from South America, 2013–2017. A test negative design
Carmen Sofia Arriola,
Nathalie El Omeiri,
Eduardo Azziz-Baumgartner,
Mark G. Thompson,
Viviana Sotomayor-Proschle,
Rodrigo A. Fasce,
Martha Von Horoch,
José Enrique Carrizo Olalla,
Walquíria Aparecida Ferreira de Almeida,
Jacqueline Palacios,
Rakhee Palekar,
Paula Couto,
Miguel Descalzo,
Alba María Ropero-Álvarez,
Cecilia Gonzalez,
Sergio Loayza,
Natalia Vergara,
Patricia Bustos,
Winston Andrade,
Carla Magda S. Domingues,
Ernesto Issac Montenegro Renoiner,
Érica Tatiane da Silva,
Swamy Lima Palmeira,
Daiana Araujo da Silva,
Ana Carolina de Lacerda Sousa,
Marilda Mendonça Siqueira,
Cynthia Vazquez,
Silvia Battaglia,
Carla Vizzotti,
Elsa Baumeister,
Carlos Giovacchini,
Nathalia Katz,
Oscar Pacheco,
Juliana Barbosa,
Diana Malo,
Paola Pulido,
Diego Garcia,
Consuelo Pinzón
Affiliations
Carmen Sofia Arriola
Influenza Division, US Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA; Corresponding authors at: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd MS A-32, Atlanta, GA 30333, USA (C. Sofia Arriola). Pan American Health Organization, 525 Twenty Third St., NW, Washington, DC 20037-2895, USA (N. El Omeiri).
Nathalie El Omeiri
Department of Family Gender and Life Course/Immunization, Pan American Health Organization/World Health Organization (PAHO/WHO), Washington, DC, USA; Corresponding authors at: Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd MS A-32, Atlanta, GA 30333, USA (C. Sofia Arriola). Pan American Health Organization, 525 Twenty Third St., NW, Washington, DC 20037-2895, USA (N. El Omeiri).
Eduardo Azziz-Baumgartner
Influenza Division, US Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA
Mark G. Thompson
Influenza Division, US Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA
Viviana Sotomayor-Proschle
Epidemiology Department, Ministry of Health, Chile
Rodrigo A. Fasce
Public Health Institute, Ministry of Health, Chile
Martha Von Horoch
Health Surveillance Unit, Ministry of Public Health and Social Welfare, Paraguay
José Enrique Carrizo Olalla
Epidemiology Department, Ministry of Health, Argentina
Walquíria Aparecida Ferreira de Almeida
Department of Communicable Diseases Surveillance, Ministry of Health, Brazil
Jacqueline Palacios
Ministry of Health, Colombia
Rakhee Palekar
Department of Public Health Emergencies, PAHO/WHO, Washington, DC, USA
Paula Couto
Department of Public Health Emergencies, PAHO/WHO, Washington, DC, USA
Miguel Descalzo
PAHO/WHO International Consultant, USA
Alba María Ropero-Álvarez
Department of Family Gender and Life Course/Immunization, Pan American Health Organization/World Health Organization (PAHO/WHO), Washington, DC, USA
Background: In 2013, the Pan American Health Organization established a multi-site, multi-country network to evaluate influenza vaccine effectiveness (VE). We pooled data from five consecutive seasons in five countries to conduct an analysis of southern hemisphere VE against laboratory-confirmed influenza hospitalizations in young children and older adults. Methods: We used a test-negative design to estimate VE against laboratory-confirmed influenza in hospitalized young children (aged 6─24 months) and older adults (aged ≥60 years) in Argentina, Brazil, Chile, Colombia, and Paraguay. Following country-specific influenza surveillance protocol, hospitalized persons with severe acute respiratory infections (SARI) at 48 sentinel hospitals (March 2013–December 2017) were tested for influenza virus infection by rRT-PCR. VE was estimated for young children and older adults using logistic random effects models accounting for cluster (country), adjusting for sex, age (months for children, and age-in-year categories for adults), calendar year, country, preexisting conditions, month of illness onset and prior vaccination as an effect modifier for the analysis in adults. Results: We included 8426 SARI cases (2389 children and 6037 adults) in the VE analyses. Among young children, VE against SARI hospitalization associated with any influenza virus was 43% (95%CI: 33%, 51%) for children who received two doses, but was 20% (95%CI: −16%, 45%) and not statistically significant for those who received one dose in a given season. Among older adults, overall VE against SARI hospitalization associated with any influenza virus was 41% (95%CI: 28%, 52%), 45% (95%CI: 34%, 53%) against A(H3N2), 40% (95%CI: 18%, 56%) against A(H1N1)pdm09, and 20% (95%CI: −40%, 54%) against influenza B viruses. Conclusions: Our results suggest that over the five-year study period, influenza vaccination programs in five South American countries prevented more than one-third of laboratory confirmed influenza-associated hospitalizations in young children receiving the recommended two doses and vaccinated older adults. Keywords: Influenza vaccine effectiveness, Children, Adults, Southern hemisphere, Latin America, Severe acute respiratory infections, Test-negative case-control design, Hospitalizations
