Influenza vaccine effectiveness in preventing hospitalizations with laboratory-confirmed influenza in Greece during the 2014-2015 season: A test-negative study

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.

Effectiveness of influenza vaccines in preventing severe influenza illness among adults: A systematic review and meta-analysis of test-negative design case-control studies

“…Due to the limited number of TND studies reporting very severe outcomes, 45,52,88 we could not compute pooled IVE against ICU admission associated with laboratory confirmed influenza. Castilla et al 88 reported a higher IVE against ICU compared to hospitalized influenza and concluded that vaccination lowered the severity of hospitalized cases of influenza.…”

Safety and efficacy of Sinopharm vaccine (BBIBP-CorV) in elderly population of Faisalabad district of Pakistan

“…We compared vaccination status in symptomatic adults who had PCR confirmed SARS-CoV-2 infection (case participants) with vaccination status in adults who reported symptoms of COVID-19 but had a negative PCR test for SARS-CoV-2 (control participants). Test negative case–control designs are considered powerful enough to estimate vaccine effectiveness and are used extensively for estimating effectiveness of influenza vaccines and vaccines against other respiratory viruses 14 15. They have been found to have high concordance with findings in randomised controlled trials 16…”

Healthcare-associated infections: potential for prevention through vaccination

“…Influenza vaccination can offer substantial protection against hospitalization, even in years in which there is a degree of antigenic drift. 47 Hepatitis B virus Nosocomial transmission of hepatitis B virus has been documented since at least the early 1980s, 48,49 although the phenomenon was described more frequently and in ever more surprising forms in the 1990s. 50 Hepatitis B vaccines have not only resulted in global reductions in the burden of liver disease caused by hepatitis B virus, but also have conferred protection in the healthcare setting, especially for healthcare workers.…”

“…Influenza vaccination can offer substantial protection against hospitalization, even in years in which there is a degree of antigenic drift. 47…”