Pfizer's COVID-19 vaccine found effective in big 'real world' test, prevents illness and death

Pfizer's COVID-19 vaccine found effective in big 'real world' test, prevents illness and death

Pfizer's COVID-19 vaccine was 92% effective at preventing severe disease after two shots and 62% after one. Its estimated effectiveness for preventing death was 72% two to three weeks after the first shot, a rate that may improve as immunity builds over time.