How Does the Body React to the COVID-19 Vaccine?
First appearing in China near the end of 2019, COVID-19 spread to North America and Europe by February 2020. By November 2020, two major pharmaceutical manufacturers had developed vaccines that were shown to be about 95% effective, which means vaccinated test subjects were 95% less likely to get COVID-19 than unvaccinated ones. The U.S. Food and Drug Administration (FDA) approved these vaccines for use within about a year of their inception. Prior to this, the shortest time in which a vaccine had been both developed and FDA approved was four years: for the mumps vaccine, introduced in 1967. At time of writing, there are three primary vaccines in use in the United States, generally known by the names of their manufacturers: Pfizer, Moderna and Johnson & Johnson.

