For everything else, including when it’s cool to take Tylenol and what to do if you missed your second dose, VICE consulted several experts on the COVID-19 vaccine to get your most pressing vax-related questions answered. The vaccine gives a pretty standard immunity to those who get it, which is a key step in reaching herd immunity, Dery said. Data on how effective just the first dose of the Pfizer or Moderna vaccine is varies across studies. The sooner you get your second dose done, the sooner we all can re-enter the world and do all the things we miss doing. If the doses are the same thing, why does the second shot seem to make people so much sicker with side effects?