Influenza vaccine effectiveness in preventing hospitalizations with laboratory-confirmed influenza in Greece during the 2014-2015 season: A test-negative study.
Τίτλος | Influenza vaccine effectiveness in preventing hospitalizations with laboratory-confirmed influenza in Greece during the 2014-2015 season: A test-negative study. |
Publication Type | Journal Article |
Year of Publication | 2016 |
Authors | Lytras, T., Kossyvakis A., Melidou A., Andreopoulou A., Exindari M., Gioula G., Kalliaropoulos A., Tryfinopoulou K., Pogka V., Spala G., Malisiovas N., & Mentis A. |
Journal | J Med Virol |
Volume | 88 |
Issue | 11 |
Pagination | 1896-904 |
Date Published | 2016 11 |
ISSN | 1096-9071 |
Λέξεις κλειδιά | Adolescent, Adult, Antigens, Viral, Case-Control Studies, Child, Child, Preschool, Clinical Laboratory Techniques, Epidemiological Monitoring, Female, Genetic Drift, Greece, Hospitalization, Humans, Infant, Influenza A Virus, H1N1 Subtype, Influenza A Virus, H3N2 Subtype, Influenza B virus, Influenza Vaccines, Influenza, Human, Male, Middle Aged, Research Design, Seasons, Vaccination, Vaccine Potency, Young Adult |
Abstract | The 2014-2015 influenza season was marked by circulation of antigenically drifted A/H3N2 strains, raising the possibility of low seasonal influenza Vaccine Effectiveness (VE). We assessed VE against hospitalization with laboratory-confirmed influenza for the 2014-2015 season, using routine surveillance data. Non-sentinel swab samples from Greek hospital inpatients were tested for influenza by RT-PCR in three laboratories, covering the entire country. We estimated VE using a test-negative design. Out of 883 patients with known vaccination status, 161 (18.2%) were vaccinated, and 392/883 patients (44.4%) tested positive for influenza, of whom 162 (41.3%) had type B and 151 (38.5%) had A/H3N2. Adjusted VE was 31.6% (95%CI: 2.9-51.8%) against any influenza, 46.8%, 95%CI: 12.5-67.6%) against type B and -1.9%, 95%CI: -69.5 to 38.7%) against A/H3N2. VE against non-ICU hospitalization appeared to be higher, but the difference did not reach statistical significance. Circulating A/H3N2 viruses showed substantial antigenic drift, while about half of the type B strains were similar to the vaccine strain. Despite the antigenic drift of the A/H3N2 strains, the vaccine still offered substantial protection against hospitalization with laboratory-confirmed influenza, mostly due to a surge in type B influenza late in the season. Vaccine coverage was low, even among groups targeted for vaccination, and considerable effort should be made to improve it. J. Med. Virol. 88:1896-1904, 2016. © 2016 Wiley Periodicals, Inc. |
DOI | 10.1002/jmv.24551 |
Alternate Journal | J. Med. Virol. |
PubMed ID | 27088266 |