Reports are trickling in of people who contracted COVID-19 even though they were vaccinated, like these four people in Oregon and these 12 in Hawaii. But these are just a few cases out of millions vaccinated. New research confirms that the vaccines are overwhelmingly effective in real-world use, and that breakthrough cases like these are rare.
According to the phase 3 studies that were required before the vaccines could be approved, the Moderna vaccine worked out to be 94% effective against symptomatic infection and the Pfizer vaccine 95% effective. These numbers refer to vaccine efficacy, a number calculated from lab trials. If the number of cases in a group of vaccinated people is 5% as many as in the control group, that vaccine has an efficacy of 95%. It’s an important number to calculate in a trial, but it’s not the same as real-world effectiveness.
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