Author(s):
Rodrigues, Emanuel 
; Machado, Ausenda ; Nunes, Baltazar
Date: 2012
Persistent ID: http://hdl.handle.net/10400.18/1087
Origin: Repositório Científico do Instituto Nacional de Saúde
Subject(s): Influenza Impact; Excess Hospitalizations; Vaccine; Estados de Saúde e de Doença
Description
Abstract publicado em: http://www.springerlink.com/content/45745132180p7215/ Background: Influenza virus circulate every year, causing epidemics usually benign for the human population, but that can degenerate into severe disease, like pneumonia. This is particularly the case in specific groups, like the elderly, with higher risk of complications associated with influenza leading to hospitalization or death.
Objective: Estimate excess number of hospitalizations from pneumonia or influenza (P&I) (ICD-9:480-487) as main diagnosis during influenza epidemics from seasons 1998-1999 to 2009-2010 in Portugal mainland (total and age groups). Measure the correlation between excess number of hospitalizations from P&I, and influenza vaccine coverage in the elderly. Compare P&I excess number of hospitalizations age distribution during seasonal epidemics with (H1N1) 2009.
Methods: Weekly P&I hospitalizations extracted from the National Hospital Discharge database (1998-2010).
Information on Influenza epidemic periods and dominant type of virus was defined from data from the national influenza surveillance system. Influenza vaccine coverage (IVC) was obtained from telephone surveys conducted by INSA.
Age-specific baseline hospitalization rates, estimated by ARIMA model without time periods associated with excess number of hospitalizations, using Flubase R package. Excess numbers of hospitalizations were calculated by subtracting expected hospitalizations rates from the observed members during influenza epidemic periods. Correlation between excess number of hospitalizations and IVC was measured with Spearman rho coefficient.
Results: Average excess number of hospitalizations per season was 1,826 (0 to 4,129), with seasonal average rate of 14.8 per 100,000 inhabitants.
During epidemics with A(H3) age groups that most contributed for excess number of hospitalizations were 65+ (72%) and 0-4 (13%). On the other hand epidemics with influenza B dominance showed a reverse pattern with a higher contribution of 0-4 (62%) and the elderly (19%). Regarding the pandemic season, ages groups with most relevant contribution was 20-49 (50%); 5-19 (18%) and 50-64 (17%); extreme age groups 0-4 and 65+ contributed with 13% and 4% respectively.
Excluding the pandemic season, correlation between excess number of hospitalizations and IVC in the elderly was -0.268, but not significant. Restricting to A(H3) dominant epidemics a significant correlation (-0.757) was observed.
Conclusion:
Influenza associated P&I excess number of hospitalizations pattern differs between age groups and dominant virus in different epidemic periods. Results suggest that at population level, increase in vaccine coverage is associated with a decrease of excess number of hospitalizations during A(H3) influenza dominated seasons.
