Breakthrough case reporting: Once again, outside researchers do the CDC’s job

In May, the CDC switched from tracking and reporting all cases that occur in vaccinated Americans to reporting only those that cause hospitalizations or deaths. At the time, I criticized this move as a lazy choice that left the U.S. without critical information as Delta and other variants spread through the country.

Now, Delta is causing the vast majority of cases—and the CDC still isn’t reporting on non-severe breakthroughs. As a result, entities outside the federal government are once again compiling data from states in order to fill in gaps left by the national public health agency.

On Friday, both Bloomberg and NBC published breakthrough case analyses. Bloomberg reported 112,000 total breakthrough cases from 35 states, as of the end of July. This is a tiny fraction of the vaccinated population—over 164 million Americans—but it is far higher than the national breakthrough case number reported by the CDC in May, pre-reporting switch.

Bloomberg’s report includes plenty of expert critiques of the CDC’s May decision, suggesting that the lack of data led to many local public health officials flying blind as Delta spread.

With better understanding of how delta spreads, different public health measures or warnings could have been put in place for vaccinated people, said Rachael Piltch-Loeb, a Harvard Chan School of Public Health researcher on public health emergency responses.

According to NBC, America’s breakthrough case total is even higher: at least 125,000 cases from 38 states. Nine states, including Pennsylvania and Missouri, failed to provide NBC with any breakthrough case information, while 11 did not provide death and hospitalization numbers. Still, these cases have clearly increased substantially in the past two months, NBC reports:

In Utah on June 2, 2021, just 27 or 8 percent of the 312 new cases in the state were breakthrough cases. As of July 26 there were 519 new cases and almost 20 percent or 94 were breakthroughs, according to state data.

Now, it’s important to emphasize that breakthrough cases are still very rare and very mild, compared with non-breakthrough COVID-19. The 125,000 cases reported by NBC comprise less than 0.08% of the 164 million Americans who’ve been fully vaccinated. And the CDC reports just 6,600 severe breakthrough cases (leading to hospitalization and/or death) as of July 26.

Any news article, headline, or tweet about breakthroughs should make that denominator explicitly clear—something that one NBC reporter failed to do when sharing his outlet’s story on Friday.

Also on Friday, the Kaiser Family Foundation (KFF) published detailed annotations on state breakthrough case reporting. 24 states and D.C. have provided public data on this topic, according to KFF; some are reporting data regularly, while others have included the information in limited press releases and other reports.

If your state is one of the 26 states not providing any public breakthrough case data at all, I’d recommend reaching out to the state public health agency and asking why not. Yes, it’s challenging to identify these cases when vaccinated people tend to have mild symptoms and might not think to get a test. And yes, the vast majority of people who have a breakthrough case will likely be fine in a couple of weeks. But the information is vital as Delta continues to wreak havoc across the country.

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