RESUMO
BACKGROUND: Vaccination is considered the most effective measure for preventing influenza and its complications. The influenza vaccine effectiveness (IVE) varies annually due to the evolution of influenza viruses and the update of vaccine composition. Assessing the IVE is crucial to facilitate decision making in public health policies. AIM: to estimate the IVE against hospitalization and its determinants in the 2021/22 season in a Spanish tertiary hospital. METHODS: We conducted a prospective observational test-negative design study within the Development of Robust and Innovative Vaccine Effectiveness (DRIVE) project. Hospitalized patients with severe acute respiratory infection (SARI) and an available influenza reverse transcription polymerase chain reaction (RT-PCR) were selected and classified as cases (positive influenza RT-PCR) or controls (negative influenza RT-PCR). Vaccine information was obtained from electronic clinical records shared by public healthcare providers. Information about potential confounders was obtained from hospital clinical registries. The IVE was calculated by subtracting the ratio of the odds of vaccination in cases and controls from one, as a percentage (IVE = (1 - odds ratio (OR)) × 100). Multivariate IVE estimates were calculated using logistic regression. RESULTS: In total, 260 severe acute respiratory infections (SARI) were identified, of which 34 were positive for influenza, and all were subtype A(H3N2). Fifty-three percent were vaccinated. Adjusted IVE against hospitalization was 26.4% (95% CI -69% to 112%). IVE determinants could not be explored due to sample size limitations. CONCLUSION: Our data revealed non-significant moderate vaccine effectiveness against hospitalization for the 2021/2022 season.
RESUMO
The objective of this study was to assess the local and systemic adverse reactions after the administration of a COVID-19 mRNA-1273 booster between December 2021 and February 2022 by comparing the type of mRNA vaccine used as primary series (mRNA-1273 or BNT162b2) and homologous versus heterologous booster in health care workers (HCW). A cross-sectional study was performed in HCW at a tertiary hospital in Barcelona, Spain. A total of 17% of booster recipients responded to the questionnaire. The frequency of reactogenicity after the mRNA-1273 booster (88.5%) was similar to the mRNA-1273 primary doses (85.8%), and higher than the BNT162b2 primary doses (71.1%). The reactogenicity was similar after receiving a heterologous booster compared to a homologous booster (88.0% vs. 90.2%, p = 0.3), and no statistically significant differences were identified in any local or systemic reactions. A higher frequency of medical leave was identified in the homologous booster dose group vs. the heterologous booster dose group (AOR 1.45; 95% CI: 1.00-2.07; p = 0.045). Our findings could be helpful in improving vaccine confidence toward heterologous combinations in the general population and in health care workers.