COVID-19 vaccine efficacy or effectiveness against severe disease remained high, although
it did decrease somewhat by 6 months after full vaccination. By contrast, vaccine
efficacy or effectiveness against infection and symptomatic disease decreased approximately
20–30 percentage points by 6 months. The decrease in vaccine efficacy or effectiveness
is likely caused by, at least in part, waning immunity, although an effect of bias
cannot be ruled out. Evaluating vaccine efficacy or effectiveness beyond 6 months
will be crucial for updating COVID-19 vaccine policy.
it did decrease somewhat by 6 months after full vaccination. By contrast, vaccine
efficacy or effectiveness against infection and symptomatic disease decreased approximately
20–30 percentage points by 6 months. The decrease in vaccine efficacy or effectiveness
is likely caused by, at least in part, waning immunity, although an effect of bias
cannot be ruled out. Evaluating vaccine efficacy or effectiveness beyond 6 months
will be crucial for updating COVID-19 vaccine policy.