Seasonal influenza vaccine effectiveness against influenza in 2012-2013: A hospital-based case-control study in Lithuania

Giedre Gefenaite*, Janette Rahamat-Langendoen, Arvydas Ambrozaitis, Aukse Mickiene, Ligita Jancoriene, Monika Kuliese, Daiva Velyvyte, Hubert Niesters, Ronald P. Stolk, Kestutis Zagminas, Eelko Hak

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)


BACKGROUND: Due to scarce information on seasonal influenza vaccine effectiveness (SIVE) against severe clinical influenza outcomes in risk populations, we conducted a case-control study to assess its effects against laboratory-confirmed influenza in hospitalized patients during the 2012-2013 influenza season.

METHODS: We conducted a test-negative case-control study among ≥18 years old patients with influenza-like illness (ILI) hospitalized in two Lithuanian hospitals. Cases were influenza A(H1N1), A(H3) or influenza B positive by RT-PCR, and controls were influenza negative. Additional demographic and clinical data to assess the role of confounding were collected. SIVE and its confidence intervals (95% CI) were estimated by using multivariate logistic regression as (1-OR)×100%.

RESULTS: The sample consisted of 185 subjects. Seasonal influenza vaccine uptake was 5%. Among 111 (60%) influenza positive cases, 24.3% were A(H1N1), 10.8% were A(H3) and 24.3% were influenza B cases. Unadjusted SIVE was 79% (95% CI -6% to 96%) and after the adjustment it increased to 86% (95% CI 19% to 97%).

CONCLUSIONS: Seasonal influenza vaccination in 2012-2013 was associated with reduced occurrence of laboratory-confirmed influenza, but due to low sample size the estimate of SIVE is imprecise. Given high prevalence of influenza in hospitalized ILI cases and low influenza vaccination coverage, there is a need to increase influenza vaccination rates.

Original languageEnglish
Pages (from-to)857-863
Number of pages7
Issue number7
Publication statusPublished - 7-Feb-2014


  • Case-control studies
  • Effectiveness
  • Influenza
  • Influenza vaccine
  • Lithuania

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