COVID cases after vaccination are still very rare—variants aren’t changing that

Enlarge / Residents wait in an observation area after receiving COVID-19 vaccines at a vaccination site in Richmond, California, on Thursday, April 15, 2021. (credit: Getty | Bloomberg)

On Tuesday, the Centers for Disease Control and Prevention released the latest data on breakthrough COVID-19 infections, which are infections among people who have been fully vaccinated against the disease. Yet again, the data suggests that the vaccines are highly effective against infection, as well as severe disease and death. The data breakdown also hints that vaccines are winning the race against variants, which don't seem to be breaking through at higher rates than expected.

Among approximately 101 million vaccinated people in the US as of April 30, the CDC collected reports of 10,262 breakthrough cases from 46 states and territories. That works out to about 0.01% breakthrough cases among the fully vaccinated. This number is almost certainly a significant undercounting, the CDC acknowledges.

Breakthrough monitoring is passive and voluntary; vaccinated people who had asymptomatic or mild COVID-19 infections may not have gotten tested or reported their cases. Only about 27 percent of the cases tallied by the CDC were considered asymptomatic. Transmission of COVID-19 was also very high during the monitoring period reported, with about 355,000 COVID-19 cases reported nationally in the week ending on April 30.

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