The COVID-19 vaccine typically takes about 1 to 2 weeks after vaccination for the body to build immunity and for the vaccine to start working effectively. This time allows the immune system to produce protective cells like T-lymphocytes and B-lymphocytes. Protection tends to be more robust after the complete initial dose series, such as after the second dose for two-dose vaccines. The vaccine's effectiveness is highest in the first few months following vaccination, with protection levels potentially waning over time, leading to recommendations for booster doses to maintain immunity.