Open AccessExcess pneumonia and influenza hospitalizations associated with influenza epidemics in Portugal from season 1998/1999 to 2014/2015
Author(s) -
Rodrigues Emanuel,
Machado Ausenda,
Silva Susana,
Nunes Baltazar
Publication year - 2018
Publication title -
influenza and other respiratory viruses
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.743
H-Index - 57
eISSN - 1750-2659
pISSN - 1750-2640
DOI - 10.1111/irv.12501
Subject(s) - medicine , excess mortality , pneumonia , influenza a virus , demography , pediatrics , covid-19 , influenza vaccine , vaccination , virus , virology , mortality rate , disease , infectious disease (medical specialty) , sociology
Background The aim of this study was to estimate excess pneumonia and influenza (P&I) hospitalizations during influenza epidemics and measure their correlation with influenza vaccine coverage in the 65 and more years old, according to the type/subtype of influenza virus. Methods The study period comprised week 40/1998‐40/2015. Age‐specific weekly P&I hospitalizations ( ICD ‐9: 480‐487) as main diagnosis were extracted from the National Hospital Discharge database. Age‐specific baseline hospitalization rates were estimated by autoregressive integrated moving average ( ARIMA ) model without time periods with excess hospitalizations. Excess hospitalizations were calculated by subtracting expected hospitalization rates from the observed during influenza epidemic periods. Correlation between excess P&I hospitalizations and influenza vaccine coverage in the elderly was measured with Pearson correlation coefficient. Results The average excess P&I hospitalizations/season was 19.4/10 5 (range 0‐46.1/10 5 ), and higher excess was observed in young children with <2 years (79.8/10 5 ) and ≥65 years (68.3/10 5 ). In epidemics with A(H3) dominant, the highest excess hospitalizations were observed among 65 and over. Seasons which influenza B or A(H1)pdm09 dominance the highest excess was observed in children with <2 years. High negative correlation was estimated between excess hospitalizations associated with A(H3) circulation and vaccine coverage in the elderly ( r = −.653; 95% CI: −0.950 to −0.137). Conclusion Over 80% of the influenza epidemics were associated with excess hospitalizations. However, excess P&I hospitalizations pattern differed from age group and circulating virus. This ecologic approach also identified a reduction in excess P&I associated with A(H3) circulation with increasing vaccine coverage in the elderly.