Pfizer COVID-19 shot efficacy wanes over time in large UK study

A U.K. analysis of more than 400,000 people who received both doses of Pfizer's COVID-19 vaccine showed the shot's efficacy waned slightly after five to six months, CNBC reported Aug. 25.

The shot was 88 percent effective at preventing COVID-19 infection one month after the second dose and 74 percent effective five to six months after the second dose.