Mortality attributable to influenza in pre-vaccination and post-vaccination periods in Argentina: An ecological study (2002-2016)

Abstract

Objectives: Compare mortality from severe acute respiratory infection (SARI) attributable to influenza between pre-vaccination (pre-V) and post-vaccination (post-V) periods, to determine the historical evolution and seasonality of time series between 2002 and 2016, and to estimate the risk of death in children between 6 and 23 months of age, using a statistical model. Methods: Time-series study using official mortality data from the official statistical database on deaths. ICD-10 codes between J09-18.9 and J22X were considered to represent SARI. Crude rates and age-adjusted rates (AAR) were calculated, and pre-V (2002-2009) and post-V (2010-2016) periods were compared using the chi-squared (χ2) test. The best statistical model was the one that compared deaths from SARI in children during 2002 with other years. The data were analyzed with R programming (p <0.05). Results: 4.6% of deaths (301,747) were from SARI, with a median age of 82 years. The percentage of deaths under age 2 declined in the post-V period (from 2.34% to 0.99%, p < 0.05). Marked seasonality was observed in winter. The AAR in persons over age 64 rose from 259.8 per 100,000 population (pre-V) to 328.6 (post-V) (p < 0.05). In children, the crude rate dropped significantly. Compared with the year 2002, there was a significantly lower estimated risk of dying from SARI during the three years post-V. Conclusions: The reduction in mortality from influenza in Argentina was more pronounced in children, with an estimated 3.5 fewer child deaths from SARI per month.