How long does it take after the second dose of a covid vaccine (either pfizer or moderna) for immunity/resistance to the virus to build up? i've always been told it takes about 2 weeks with the flu vaccine. how long for the covid vaccine?

Immunity: It is thought that some immunity builds up about one week after the first dose and reaches a peak about two weeks after the second dose.

COVID 19 vaccine: You should reach full immunity about 2 weeks after your second dose of COVID 19 vaccine.

Agree with Dr. F&C: You are expected to be immune in about 2 weeks after the second dose. However, at this stage it is still recommended that you take usual precautions of social distancing, wearing a mask and hand hygiene. Have a healthy diet, exercise 30 minutes/day, drink plenty of water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV vaccine.

Not straightforward : The Moderna vaccine maybe effective 1 week after dose two, Pfizer two weeks, but if prior infection, maybe even earlier. Best safety do TWO WEEKS and not split hairs