When does the COVID-19 booster shot become effective?

According to a preliminary study in Israel, breakthrough cases of COVID-19 were more prevalent among those who received the vaccine at an earlier date. That’s because antibody levels start to wane around six months after vaccination. “Having fewer circulating antibodies means there will be a delay in your immune response to COVID infection compared to when antibodies are circulating in greater numbers,” Dr. Shruti Gohil, an associate director of epidemiology and infection prevention at University of California Irvine Health, told Good Housekeeping.