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ObjectivesTo estimate the effectiveness of mRNA vaccines against SARS-CoV-2 infection and severe covid-19 at different time after vaccination.DesignRetrospective cohort study.SettingItaly, 27 December 2020 to 7 November 2021.Participants33 250 344 people aged ≥16 years who received a first dose of BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) vaccine and did not have a previous diagnosis of SARS-CoV-2 infection.Main outcome measuresSARS-CoV-2 infection and severe covid-19 (admission to hospital or death). Data were divided by weekly time intervals after vaccination. Incidence rate ratios at different time intervals were estimated by multilevel negative binomial models with robust variance estimator. Sex, age group, brand of vaccine, priority risk category, and regional weekly incidence in the general population were included as covariates. Geographic region was included as a random effect. Adjusted vaccine effectiveness was calculated as (1−IRR)×100, where IRR=incidence rate ratio, with the time interval 0-14 days after the first dose of vaccine as the reference.ResultsDuring the epidemic phase when the delta variant was the predominant strain of the SARS-CoV-2 virus, vaccine effectiveness against SARS-CoV-2 infection significantly decreased (PConclusionsThe results support the vaccination campaigns targeting high risk people, those aged ≥60 years, and healthcare workers to receive a booster dose of vaccine six months after the primary vaccination cycle. The results also suggest that timing the booster dose earlier than six months after the primary vaccination cycle and extending the offer of the booster dose to the wider eligible population might be warranted.

IntroductionThe overuse of antibiotics is causing worldwide spread of antimicrobial resistance (AMR). Compared with other countries, Italy has both high antibiotic consumption rates and high rates of AMR. Due to the fact that around 90% of antibiotics are prescribed by general practitioners (GPs), this study aims to measure the impact of knowledge, attitudes and sociodemographic and workplace-related factors on the quality of antibiotic prescriptions filled by GPs in the Italian Region of Sardinia.Methods and analysisKnowledge, attitude, sociodemographic and workplace-related factors deemed to influence physicians prescribing behaviour will be evaluated in a cross-sectional study conducted among all GPs of the Italian Region of Sardinia (n=1200). A knowledge and attitudes questionnaire (Knowledge and Attitudes on Antibiotics and Resistance - Italian version: ITA-KAAR) accompanied by a sociodemographic form will be linked to drug prescription data reimbursed by the National Health System. European Surveillance of Antibiotic Consumption quality indicators for outpatient antibiotic use will be calculated from drug prescription records. Every GP will be deemed to have demonstrated an adequate quality of prescriptions of antibiotics if half of the indicator score plus one is better than the median of the region. A multivariate Poisson regression model with robust variance estimation will be used to evaluate the impact of the determinants of antibiotic prescriptions on the actual prescribing quality of each physician.Ethics and disseminationThe project has been approved by the ethics committee of the Regional Health Trust of Sardinia (176/2019/CE, 24 September 2019). The results will be useful to inform evidence-based interventions to tackle irrational antibiotic use in the community.