Excess pneumonia and influenza hospitalizations associated with influenza epidemics in Portugal from season 1998/1999 to 2014/2015

Abstract

BackgroundThe 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.MethodsThe 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.ResultsThe average excess P&I hospitalizations/season was 19.4/105 (range 0‐46.1/105), and higher excess was observed in young children with <2 years (79.8/105) and ≥65 years (68.3/105). 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).ConclusionOver 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.

Burden of medically attended influenza in Norway 2008‐2017

“…The hospitalization rate during the 2009‐2010 pandemic was lower than the overall average for our study period. This is similar to findings in other countries . However, during the pandemic season, there was a marked difference in the age groups affected by severe influenza compared with regular influenza seasons.…”

“…This is similar to findings in other countries. 30,36 However, during the pandemic season, there was a marked difference in the age groups affected by severe influenza compared with regular influenza seasons. During the pandemic, the rate of hospitalization in the 0-4 year age group was the highest recorded in the study period.…”

Estimates of influenza‐associated hospitalisations in tropical Singapore, 2010‐2017: Higher burden estimated in more recent years

“…Our overall estimated excess P&I hospitalisation rate of 50.1 per 100 000 person‐years was higher than the average seasonal excess P&I hospitalisation rate of 19.4 per 100 000 persons reported by Portugal from 1998/1999 to 2014/2015, and the overall excess severe acute respiratory infection (SARI) hospitalisation rate of 20.6 per 100 000 persons reported by Oman for 2012‐2015 . It was also higher than the annual excess SARI hospitalisation rate of 13‐19 per 100 000 persons from 2013/14 to 2015/16 reported by Indonesia, which has a similar tropical climate.…”

“…There is a widespread consensus that influenza imposes a considerable burden on public health, including substantial numbers of severely ill patients resulting in hospitalisations and deaths . The impact of influenza on public health varies across seasons, mainly due to the varying influenza virus types/subtypes, vaccine uptake in the community and the match between the recommended vaccine with the circulating viruses .…”

“…There is a widespread consensus that influenza imposes a considerable burden on public health, including substantial numbers of severely ill patients resulting in hospitalisations and deaths. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The impact of influenza on public health varies across seasons, mainly due to the varying influenza virus types/subtypes, vaccine uptake in the community and the match between the recommended vaccine with the circulating viruses. [4][5][6][7][8] Quantifying the burden of influenza disease is important so as to assess the severity of the virus, evaluate how well public health services are coping with the additional burden or determine whether additional interventions should be considered to reduce the impact.…”