BackgroundVaccination, one of the most important and effective ways of preventing infectious diseases, has recently been used to control the COVID-19 pandemic. The present meta-analysis study aimed to evaluate the effectiveness of COVID-19 vaccines in reducing the incidence, hospitalization, and mortality from COVID-19.MethodsA systematic search was performed independently in Scopus, PubMed via Medline, ProQuest, and Google Scholar electronic databases as well as preprint servers using the keywords under study. We used random-effect models and the heterogeneity of the studies was assessed using I2 and χ2 statistics. In addition, the Pooled Vaccine Effectiveness (PVE) obtained from the studies was calculated by converting based on the type of outcome.ResultsA total of 54 studies were included in this meta-analysis. The PVE against SARS-COV 2 infection were 71% [odds ratio (OR) = 0.29, 95% confidence intervals (CI): 0.23–0.36] in the first dose and 87% (OR = 0.13, 95% CI: 0.08–0.21) in the second dose. The PVE for preventing hospitalization due to COVID-19 infection was 73% (OR = 0.27, 95% CI: 0.18–0.41) in the first dose and 89% (OR = 0.11, 95% CI: 0.07–0.17) in the second dose. With regard to the type of vaccine, mRNA-1273 and combined studies in the first dose and ChAdOx1 and mRNA-1273 in the second dose had the highest effectiveness in preventing infection. Regarding the COVID-19-related mortality, PVE was 68% (HR = 0.32, 95% CI: 0.23–0.45) in the first dose and 92% (HR = 0.08, 95% CI: 0.02–0.29) in the second dose.ConclusionThe results of this meta-analysis indicated that vaccination against COVID-19 with BNT162b2 mRNA, mRNA-1273, and ChAdOx1, and also their combination, was associated with a favorable effectiveness against SARS-CoV2 incidence rate, hospitalization, and mortality rate in the first and second doses in different populations. We suggest that to prevent the severe form of the disease in the future, and, in particular, in the coming epidemic picks, vaccination could be the best strategy to prevent the severe form of the disease.Systematic review registrationPROSPERO International Prospective Register of Systematic Reviews: http://www.crd.york.ac.uk/PROSPERO/, identifier [CRD42021289937].

PurposeTo evaluate the immunogenicity of COVID-19 vaccines in patients with diabetes mellitus (DM) through a systematic approach.MethodA comprehensive search was conducted in PubMed, Scopus, and Web of Science with no time restrictions. The search was based on the three main concepts: Covid-19, Vaccine immunogenicity and Diabetes Mellitus.ResultsAfter excluding irrelevant studies, 16 studies remained for the quantitative assay. Among the sixteen studies, eleven had controls. Type of diabetes was specifically mentioned in six studies (T2DM; n=4, T1DM and T2DM; n=2). Twelve of the included studies were conducted on the immunogenicity of vaccines that included mRNA vaccines (i.e. BNT162b2 and mRNA-1273) in DM, five studies included vector-based vaccines (i.e. Ad5-nCoV and ChAdOx1-S), and five studies assessed the immunogenicity of vaccines in DM, including inactivated vaccines (i.e. BBV-152, CoronaVac, Sinopharm or SinoVac). Most of the current studies indicate lower antibody response in patients with DM compared to individuals without DM, after the second dose of vaccine and irrespective of vaccine type. Several studies have shown that higher age and higher BMI are associated with lower antibody response, while optimum glycemic control and higher GFR are associated with higher antibody response among patients with DM.ConclusionImmunogenicity of the vaccines has mostly been reported to be lower among patients with DM compared to healthy controls. There are also few studies assessing variables that significantly affect this association, including age, type of diabetes, BMI, glycemic control and eGFR. Investigating these associations could help us provide the most advantageous condition for patients with DM before, during and after vaccination for optimum antibody response. Many unresolved issues concerning potential factors affecting vaccine immunogenicity, including type of vaccine, numbers of administered doses, re-vaccination intervals and hyperglycemia in patients with DM need to be addressed through future research.

Introduction & ObjectiveVaccination is one of the most important and effective ways of preventing infectious diseases, and has recently been used in the COVID-19 epidemic and pandemic. The present meta-analysis study aimed to evaluate the effectiveness of COVID-19 vaccines in reducing the incidence of infection, hospitalization, and mortality in observational studies.Materials and MethodsA systematic search was performed independently in Scopus, PubMed, ProQuest, and Google Scholar electronic databases as well as Preprint servers using the keywords under study. The heterogeneity of the studies was assessed using I2and χ2 statistics, according to which the I2 of > 50% and P -value <0.1 was reported as heterogeneity of the studies. In addition, the Pooled Vaccine Effectiveness (PVE) obtained from the studies was calculated by converting (1-Pooled estimate × 100%) based on the type of outcome.ResultsA total of 54 records were included in this meta-analysis. The rate of PVE against SARS-COV 2 infection was about 71% (OR = 0.29, 95% CI: 0.23-0.36) in the first dose and 87% (OR = 0.13, 95% CI: 0.08-0.21) in the second, and the highest effectiveness in the first and second doses was that of BNT162b2 mRNA and combined studies. The PVE versus COVID-19-associated hospitalization was 73% (OR = 0.27, 95% CI: 0.18-0.41) in the first dose and 89% (OR = 0.11, 95% CI: 0.07-0.17) in the second. mRNA-1273 and combined studies in the first dose and ChAdOx1 and mRNA-1273 in the second dose had the highest effectiveness. Regarding the COVID-19-related mortality, PVE was about 28% (HR = 0.39, 95% CI: 0.23-0.45) in the first dose and 89% (HR = 0.11, 95% CI: 0.03-0.43) in the second.ConclusionThe evidence obtained from this study showed that the effectiveness of BNT162b2 mRNA, mRNA-1273, and ChAdOx1 in the first and second doses, and even combined studies were associated with increased effectiveness against SARS-COV2 infection, hospitalization, and death from COVID-19. In addition, considering that the second dose was significantly more efficient than the first one, a booster dose injection could be effective in high-risk individuals. On the other hand, it was important to observe other prevention considerations in the first days after taking the first dose.