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Real World Evidence for COVID-19 Vaccines

Similar to clinical trials, real world cohort and case-control studies find COVID-19 infections are reduced by >90% with two doses of mRNA vaccines. Single doses of either mRNA or AstraZeneca vaccine decreases infections by ~60% and hospitalizations by 70-80%. Vaccine effectiveness appears similar for variants of concern and are safe for pregnant women. HMC


Second dose of COVID-19 Vaccination

NACI has provided updated recommendations on COVID-19 vaccine schedules. For those who have received a first dose of an AstraZeneca vaccine, an mRNA vaccine is preferred for the second dose due to emerging evidence suggesting better immune response, and, to mitigate the risk of VITT(Vaccine-Induced Thrombotic Thrombocytopenia) from viral vector vaccines. HMC


3 Approved COVID-19 Vaccines Efficacy

Interim results of two large randomized, placebo-controlled trials (RCTs) demonstrate ~95% relative efficacy in preventing COVID-19 (Pfizer, Moderna). The AstraZeneca/Oxford vaccine has ~70% relative efficacy. Absolute benefits will vary with baseline risk and time but if annual risk of developing COVID-19 is 20%, then vaccine would decrease risk to 1% (6% with AstraZeneca/Oxford). These vaccines...