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. 2018 Jan;12(1):153-160.
doi: 10.1111/irv.12501.

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

Emanuel Rodrigues  1 , Ausenda Machado  1   2 , Susana Silva  1 , Baltazar Nunes  1   2
Affiliations

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

Emanuel Rodrigues et al. Influenza Other Respir Viruses. 2018 Jan.

Abstract

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 19.4/105 (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).

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.

Keywords: autoregressive integrated moving average models; excess hospitalizations; influenza epidemics; vaccine coverage.

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Figures

Figure 1
Figure 1
Weekly P&I hospitalization rate per 100 000 inhabitants and the respective estimated baseline and baseline upper limit in the absence of the impact of influenza epidemics from 1998 to 2015
Figure 2
Figure 2
Average excess P&I hospitalization rates per predominant (sub)‐type of influenza virus by age group
Figure 3
Figure 3
Average excess P&I hospitalization rates ratios for A(H3) and A(H1)pdm09 predominant (sub)‐type of influenza virus compared to B predominant seasons by age group
Figure 4
Figure 4
Scatter plot of the vaccine coverage rates vs the excess P&I hospitalizations rate according to the dominant subtype virus for seasons 1998/1999‐2014/2015, on individuals aged 65 y or more
See this image and copyright information in PMC

References

    1. Wuerth BA, Bonnewell JP, Wiemken TL, Arnold FW. Trends in pneumonia mortality rates. Emerg Infect Dis. 2016;22:8‐12. https://doi.org/10.3201/eid2209.150680. - DOI - PMC - PubMed
    1. Park M, Wu P, Goldstein E, Joo Kim W, Cowling BJ. Influenza‐associated excess mortality in South Korea. Am J Prev Med. 2016;50:e111‐e119. https://doi.org/10.1016/j.amepre.2015.09.028. - DOI - PMC - PubMed
    1. Khieu TQT, Pierse N, Telfar‐Barnard LF, Huang QS, Baker MG. Estimating the contribution of influenza to hospitalisations in New Zealand from 1994 to 2008. Vaccine. 2015;33:4087‐4092. https://doi.org/10.1016/j.vaccine.2015.06.080. - DOI - PubMed
    1. Serfling RE. Methods for current statistical analysis of excess pneumonia‐influenza deaths. Public Health Rep. 1963;78:494‐506. - PMC - PubMed
    1. Thompson WW, Shay MDDK, Weintraub E, et al. Influenza‐associated hospitalizations in the United States. JAMA. 2004;292:1333‐1340. https://doi.org/10.1001/jama.292.11.1333. - DOI - PubMed

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