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BackgroundThere is a need for evaluation regarding vaccine effectiveness (VE) and the urgency of booster vaccination against Covid-19 B.1.1.529 (Omicron) variant. MethodsSystematic search was conducted on April 6th, 2022, on databases (PubMed, ScienceDirect, CENTRAL, Web of Science, Scopus). VE difference (VED) estimates were assessed using random-effects model and DerSimonian-Laird tau estimators. Two models result, i.e., within 3 months and within 3 months or more, are compared. VE versus time meta-regression analysis was evaluated using mixed-effects model with Restricted-Maximum Likelihood tau estimators and Hartung-Knapp adjustments. FindingsAd26.COV2.S, BNT162b2, ChAdOx1 nCov-19, and mRNA-1273 vaccines were included in the analyses. Compared to full dose, booster dose of overall vaccines provided better protection against any (VED=22% (95%CI 15%-29%), p<0.001), severe (VED=20% (95%CI 8%-32%), p=0.001) and symptomatic (VED=22% (95%CI 11%-34%), p<0.001) Omicron infections within 3 months, as well as within 3 months or more (VED=30% (95%CI 24%-37%), p<0.001 for any, VED=18% (95%CI 13%-23%), p<0.001 for severe and VED=37% (95%CI 29%-46%), p<0.001 for symptomatic infections). The meta-regression analysis of overall vaccines revealed that the full dose VE against any and symptomatic Omicron infections were significantly reduced each month by 3.0% (95%CI 0.9%-4.8%, p=0.004) and 5.2% (95%CI 3.3%-7.1%, p=0.006), respectively; whereas booster dose effectiveness against severe and symptomatic Omicron infections were decreased by 3.7% (95%CI 5.1%-12.6%, p=0.030) and 3.9% (95%CI 1.2%-6.5%, p=0.006), respectively. InterpretationCompared to full dose only, a booster dose addition provides better protection against B.1.1.529 infection. Although the VE estimates of Ad26.COV2.S, BNT162b2, ChAdOx1 nCov-19, and mRNA-1273 vaccines against B.1.1.529 infection after both full and booster doses are generally moderate, and the booster dose provides excellent protection against severe infection, it is important to note that the VE estimates decline over time, suggesting the need for a regular Covid-19 booster injection after certain period of time to maintain VE.
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ObjectivesThe use of monoclonal antibody for COVID-19 showed conflicting results in prior studies and its efficacy remains unclear. We aimed to comprehensively determine the efficacy and safety profile of monoclonal antibodies in COVID-19 patients. MethodsSixteen RCTs were analyzed using RevMan 5.4 to measure the pooled estimates of risk ratios (RRs) and standardized mean differences (SMDs) with 95% CIs. ResultsThe pooled effect of monoclonal antibodies demonstrated mortality risk reduction (RR=0.89 (95%CI 0.82-0.96), I2=13%, fixed-effect). Individually, tocilizumab reduced mortality risk in severe to critical disease (RR=0.90 (95%CI 0.83-0.97), I2=12%, fixed-effect)) and lowered mechanical ventilation requirements (RR=0.76 (95%CI 0.62-0.94), I2=42%, random-effects). Moreover, it facilitated hospital discharge (RR=1.07 (95%CI 1.00-1.14), I2=60%, random-effects). Meanwhile, bamlanivimab-etesevimab and REGN-COV2 decrease viral load ((SMD=-0.33 (95%CI -0.59 to -0.08); (SMD=-3.39 (95%CI -3.82 to -2.97)). Interestingly, monoclonal antibodies did not improve hospital discharge at day 28-30 (RR=1.05 (95%CI 0.99-1.12), I2=71%, random-effects) and they displayed similar safety profile with placebo/standard therapy (RR=1.04 (95%CI 0.76-1.43), I2=54%, random-effects). ConclusionTocilizumab improved hospital discharge and reduced mortality as well as the need for mechanical ventilation, while bamlanivimab-etesevimab and REGN-COV2 reduced viral load in mild to moderate outpatients. In general, monoclonal antibodies are safe and should be considered in severe to critical COVID-19 patients. RegistrationPROSPERO (CRD42021235112)
