Number of COVID-19 ‘breakthrough cases’ lower than expected

Given the number of people fully vaccinated in the U.S.—more than 87 million as of April 20, 2021, according to the Centers for Disease Control and Prevention—the roughly 7,150 so-called “breakthrough cases” of COVID-19 that have been reported is extremely low, according to experts.

“Overall, I am completely surprised that the breakthrough numbers of people in the States is as low as it is,” said Barry Bloom, Joan L. and Julius H. Jacobson Research Professor of Public Health, in an April 22, 2021, Slate article. “And we should be grateful for that.” Bloom and other experts quoted in the article said that some breakthrough cases are normal and expected.

Stephen Kissler, research fellow in the Department of Immunology and Infectious Diseases, said that it’s possible that the proportion of breakthrough cases will increase, because most people were vaccinated recently and haven’t had much time to be exposed. He said it’s also possible that the reported numbers are low because some vaccinated people could have symptomatic breakthrough infections but might not get tested, assuming they can’t be sick with COVID-19.

He added, though, that he doesn’t expect the proportion of breakthrough cases to increase much “because of how effective the vaccine is, both at preventing disease and reducing transmission.”

Read the Slate article: The Really Surprising Thing About Fully Vaccinated People Who Get COVID-19