Federal health officials this month decided to limit how they monitor vaccinated people who have been infected with Covid-19, drawing concern from some scientists who say that may mean missing needed data showing why and how it happens.
At the start of May, the CDC shifted from monitoring all reported breakthroughs to only those that result in hospitalization or death, Tom Clark, head of the vaccine evaluation unit for the CDC’s vaccine task force, said in an interview. The goal of the new strategy, according to the agency: maximize the quality of data collected on cases.