Two doses are needed for the two COVID-19 vaccines from Pfizer and Moderna. The time between the doses depends on the vaccine you are getting. The Pfizer vaccine must be given 21 days (three weeks) apart and the Moderna vaccine must be given 28 days apart (four weeks).
It is very important that you get both vaccine doses, the same product for each dose, and that the doses are given at the correct time apart. The vaccine is only fully effective with both doses of vaccine. If someone only gets one dose, they may not be protected (immune) against COVID-19.
After the second dose, it takes about two weeks for your body to build up protection, so it’s about six weeks total from the first vaccine dose to when you should be fully protected.