Credit: Gov. Tom Wolf
More than 200 million U.S. residents have gotten at least one shot of a COVID-19 vaccine with the expectation that the vaccines slow virus transmission and save lives.
standard for medical research. The studies found the vaccines to be very effective at preventing severe COVID–19 and especially good at preventing death. But it’s important to track any new treatment in the real world as the population-level benefits of vaccines could differ from the efficacy found in clinical trials.
For instance, some people in the U.S. have only been getting the first shot of a two-shot vaccine and are therefore less protected than a fully vaccinated person. Alternatively, vaccinated people are much less likely to transmit COVID-19 to others, including those who are not vaccinated. This could make vaccines more effective at a population level than in the clinical trials.
