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ABSTRACTThis review quantified the association of vaccine literacy (VL) and vaccination intention and status. PubMed, Scopus, and Web of Science were searched. Any study, published until December 2022, that investigated the associations of interest were eligible. For each outcome, articles were grouped according to the vaccine administrated and results were narratively synthesized. Inverse-variance random-effect models were used to compare standardized mean values in VL domain(s) between the two groups: individuals willing vs. unwilling to get vaccinated, and individuals vaccinated vs. unvaccinated. This review of 18 studies shows that VL strongly predicts the vaccination intention while its association with vaccination status is attenuated and barely significant, suggesting that other factors influence the actual vaccination uptake. However, given the scarce evidence available, the heterogeneity in the methods applied and some limitations of the studies included, further research should be conducted to confirm the role of VL in the vaccination decision-making process.

The addictive protection against SARS-CoV-2 reinfection conferred by vaccination, as compared to natural immunity alone, remains to be quantified. We thus carried out a meta-analysis to summarize the existing evidence on the association between SARS-CoV-2 vaccination and the risk of reinfection and disease. We searched MedLine, Scopus and preprint repositories up to July 31, 2022, to retrieve cohort or case-control studies comparing the risk of SARS-CoV-2 reinfection or severe/critical COVID-19 among vaccinated vs. unvaccinated subjects, recovered from a primary episode. Data were combined using a generic inverse-variance approach. Eighteen studies, enrolling 18,132,192 individuals, were included. As compared to the unvaccinated, vaccinated subjects showed a significantly lower likelihood of reinfection (summary Odds Ratio—OR: 0.47; 95% CI: 0.42–0.54). Notably, the results did not change up to 12 months of follow-up, by number of vaccine doses, in studies that adjusted for potential confounders, adopting different reinfection definitions, and with different predominant strains. Once reinfected, vaccinated subjects were also significantly less likely to develop a severe disease (OR: 0.45; 95% CI: 0.38–0.54). Although further studies on the long-term persistence of protection, under the challenge of the new circulating variants, are clearly needed, the present meta-analysis provides solid evidence of a stronger protection of hybrid vs. natural immunity, which may persist during Omicron waves and up to 12 months.

Mandatory vaccination (MV) against COVID-19 is a contentious topic. In this study, we used logistic regression models to identify attitudes among Sapienza University students towards MV for COVID-19. We considered three different scenarios: mandatory COVID-19 vaccination (MCV) for healthcare workers (HCWs) (Model 1), for all people aged ≥ 12 years (Model 2), and for admission to schools and universities (Model 3). We collected 5287 questionnaires over a six-month period and divided these into three groups (September–October 2021, November–December 2021, and January–February 2022). MCV for HCWs was the most strongly supported policy (69.8% in favour), followed by MCV for admission to schools and universities (58.3%), and MCV for the general population (54.6%). In a multivariable analysis, the models showed both similarities and differences. There was no association of socio-demographic characteristics with the outcomes, apart from being enrolled in non-healthcare courses, which negatively affected Models 2 and 3. A greater COVID-19 risk perception was generally associated with a more positive attitude towards MCV, although heterogeneously across models. Vaccination status was a predictor of being in favour of MCV for HCWs, whereas being surveyed in November–February 2022 favoured MCV for admission to schools and universities. Attitudes towards MCV were variable across policies; thus, to avoid unintended consequences, these aspects should be carefully considered by policymakers.

Despite the availability of effective and safe vaccines, the acceptance of COVID-19 vaccination is suboptimal. In this meta-analysis we quantified the prevalence estimates of COVID-19 vaccine acceptance with a specific focus on worldwide geographical differences. We searched PubMed, Scopus, Web of Science and PsycInfo up to April 2021 (PROSPERO ID: CRD42021235328). Generalized random-effects linear models with a logit link were used to calculate the pooled estimated rate of vaccine acceptance at both the global and regional level. A meta-regression analysis was performed to assess the association between COVID-19 vaccine acceptance and various characteristics of the studies. Overall, 71 articles yielding 128 prevalence estimates were included. The pooled prevalence of COVID-19 vaccination acceptance rate was 66% (95% CI: 61–71%). This varied by geographic area, ranging from 36% (95% CI: 18–60%) in Africa to 83% (95% CI: 82–84%) in Oceania, and there was high variability between countries (15.4% Cameroon–100% Bhutan). Meta-regression analysis showed that studies that investigated COVID-19 vaccination intentions using multiple choice/scoring gave a vaccine acceptance prevalence lower than studies with only two possible answers (yes/no) (ß: −1.02 95% CI: −1.41 to −0.63). Despite some variation in the estimates, the results showed that one in three people may refuse/delay COVID-19 vaccination.