Effectiveness of pandemic and seasonal influenza vaccines in preventing pandemic influenza-associated hospitalization

Department de Salut Pública, Universitat de Barcelona, Barcelona, Spain.
Vaccine (Impact Factor: 3.62). 07/2012; 30(38):5644-50. DOI: 10.1016/j.vaccine.2012.06.090
Source: PubMed

ABSTRACT Vaccines are leading pharmacological measures for limiting the impact of pandemic influenza in the community. The objective of this study was to investigate the effectiveness of influenza (pandemic and seasonal) vaccines in preventing pandemic influenza-associated hospitalization. We conducted a multicenter matched case-control study in 36 Spanish hospitals. Patients hospitalized with confirmed pandemic influenza between November 2009 and February 2010 and two hospitalized controls per case, matched according to age, date of hospitalization and province of residence, were selected. Multivariate analysis was performed using conditional logistic regression. Subjects were considered vaccinated if they had received the vaccine >14 days (seasonal influenza vaccine) or >7 days (pandemic influenza vaccine) before the onset of symptoms (cases) or the onset of symptoms of the matched case (controls). For the pandemic influenza vaccine, vaccination effectiveness (VE) was estimated taking into account only patients recruited from November 23, 2009, seven days after the beginning of the pandemic influenza vaccination campaign. 638 cases and 1250 controls were included. The adjusted VE of the pandemic vaccine in the ≥18 years age group was 74.2% (95% CI, 29-90) and that of the influenza seasonal vaccine 15.0% (-34 to 43). The recommendation of influenza vaccination should be reinforced as a regular measure to reduce influenza-associated hospitalization during pandemics and seasonal epidemics.

Download full-text


Available from: Vicente Martín, Sep 29, 2015
1 Follower
22 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background. In most seasons, the influenza vaccine is effective in preventing influenza, but it is not clear whether it is equally effective in preventing mild and severe cases. We designed a case-control study to compare the effectiveness of the influenza vaccine in preventing out-patient, in-patient and severe or fatal cases of laboratory-confirmed influenza. Methods. Hospitalized patients (n=691) with laboratory-confirmed influenza in the 2010-2011 season recruited in 29 Spanish hospitals were individually matched by age, admission/visit date and province, with an out-patient with laboratory-confirmed influenza and an out-patient control. Severe cases were considered those admitted to intensive care units or who died in the hospital (n=177). We compared the influenza vaccine status of controls and out-patient cases, in-patient cases and severe cases using conditional logistic regression adjusted for potential confounding factors. Severe and non-severe in-patient influenza cases were compared using unconditional logistic regression. Vaccine effectiveness was (1-odds ratio) x100. Results. Adjusted vaccine effectiveness was 75% (odds ratio [OR]: 0.25; 95% confidence interval [CI], 0.16-0.39) in preventing influenza out-patient cases, 60% (OR:0.40; 95% CI, 0.25-0.63) in preventing influenza-associated hospitalizations, and 89% (OR:0.11; 95% CI, 0.04-0.37) in preventing severe cases. In in-patient cases, influenza vaccination was associated with a lower risk of severe influenza (OR, 0.42; 95% CI, 0.22-0.80). Conclusions. Influenza vaccination prevented influenza cases and hospitalizations and was associated with a better prognosis in in-patients with influenza. The combined effect of these two mechanisms would explain the high effectiveness of the vaccine in preventing severe cases due to influenza.
    Clinical Infectious Diseases 03/2013; · 8.89 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Influenza vaccine is moderately effective for preventing influenza illness. It is not known if vaccination reduces the risk of subsequent hospital admission among patients with vaccine failure and laboratory confirmed influenza illness. Patients in a community cohort presenting with acute respiratory illness were prospectively enrolled and tested for influenza during 8 seasons to estimate seasonal vaccine effectiveness. Hospital admissions within 14 days after illness onset were identified for all participants aged ≥20 years with laboratory confirmed influenza. The association between vaccination and hospital admission was examined in a propensity score adjusted logistic regression model. The model was validated by examining the association between vaccination and hospital admission in participants without influenza. Influenza was identified in 1393 (28%) of 4996 participants. Sixty-two (6%) of 1020 with influenza A and 17 (5%) of 369 with influenza B were hospitalized. Vaccination was not associated with a reduced risk of hospital admission among all participants with influenza [adjusted odds ratio (aOR)=1.08; 95% CI: 0.62, 1.88]; or among those with influenza A (aOR=1.35; 95% CI: 0.71, 2.57) or influenza B (aOR=0.67; 95% CI: 0.21,2.15). Influenza vaccination was not associated with hospitalization after non-influenza respiratory illness (aOR=1.14; 95% CI: 0.84, 1.54). Influenza vaccination did not reduce the risk of subsequent hospital admission among patients with vaccine failure. These findings do not support the hypothesis that vaccination mitigates influenza illness severity.
    Vaccine 11/2013; 32(4). DOI:10.1016/j.vaccine.2013.11.060 · 3.62 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Online surveys are increasingly used due to their speed and efficiency. The aim of this study was to analyze factors that may have contributed to the quality and speed of response of an online survey on influenza vaccination in primary healthcare workers. A multicenter study including family physicians, nurses and pediatricians from primary healthcare teams from seven Spanish Autonomous Communities was designed. The centers were selected by simple random sampling. The survey remained active and accessible for 56 days and four reminders were sent. The odds ratios (OR) and their 95% confidence intervals (CI) were calculated to assess the association of sociodemographic variables and responding to the survey before the second reminder. Complete, validated information was obtained from 1965 primary healthcare workers. The total response rate was 36.2%. More nurses (46.3%) responded before the second reminder and more family physicians (52.8%) after the second reminder. The adjusted OR shows that family physicians responded later (AOR 1.46, 95% CI 1.2-1.8) than nurses. The responses obtained in the first 24 h after the initial sending and the reminders accounted for 41.7% of the completed surveys, indicating the importance of reminders.
    International journal of environmental research and public health 01/2015; 12(1):541-53. DOI:10.3390/ijerph120100541 · 2.06 Impact Factor