BACKGROUND:  The 2014-2015 influenza season was severe, with widespread circulation of influenza A (H3N2) viruses that were antigenically drifted from the vaccine virus. Reported vaccine effectiveness (VE) estimates from ambulatory care settings were markedly decreased. METHODS:  Adults, hospitalized at two hospitals in southeast Michigan for acute respiratory illnesses, defined by admission diagnoses, of ≤10 days duration were prospectively enrolled. Throat and nasal swab specimens were collected, combined, and tested for influenza by RT-PCR. VE was estimated by comparing the vaccination status of those who tested positive for influenza with those who tested negative in logistic regression models adjusted for age, sex, hospital, calendar time, time from illness onset to specimen collection, frailty score, and Charlson Comorbidity Index (CCI). RESULTS:  Among 624 patients included in the analysis, 421 (68%) were considered vaccinated, 337 (54%) were female, 220 (35%) were age ≥65 years, and 92% had CCI >0 indicating ≥1 comorbid conditions. 98 (16%) patients tested positive for influenza A (H3N2); among 60 (61%) A (H3N2) viruses tested by pyrosequencing, 53 (88%) belonged to the drifted 3C.2a genetic group. Adjusted VE was 43% (95% CI: 4 to 67) against influenza A (H3N2); 40% (95% CI: -13 to 68) for those <65 years of age and 48% (95% CI: -33 to 80) for those ≥65. Sensitivity analyses largely supported these estimates. CONCLUSIONS:  VE estimates appeared higher than reports from similar studies in ambulatory care settings, suggesting that the 2014-15 vaccine may have been more effective in preventing severe illness requiring hospitalization.

Fonte: Influenza Vaccine Effectiveness against Antigenically Drifted Influenza Higher than Expected in Hospitalized Adults: 2014-2015 | Read by QxMD

Taxas de eficácia abaixo de 50% e ainda assim resultados muito melhores do que em anos anteriores. Definitivamente precisamos de vacinas com capacidade de proteção em patamares superiores a estes.