CDC Hasn't Updated COVID Vax Breakthrough Data

As Americans weigh the risks of holiday gatherings, many are looking for data on COVID-19 breakthrough cases, hospitalizations, and deaths among the vaccinated -- but nationally, that information is not reported in real-time.

In mid-October, the CDC started publishing cases and deaths by vaccination status on its COVID Data Tracker for the first time. But the information was only current as of September 4 -- and the page hasn't been updated since.

In addition, the CDC's page on breakthrough hospitalizations by vaccination status is only current through the end of August.

"It's definitely a problem that here in the U.S., we have not had real-time, reliable data on breakthrough infections," said Leana Wen, MD, a professor of health policy and management at George Washington University. "Why should we be waiting until we see Americans end up in the hospital with breakthrough infections before we take action and recommend boosters more broadly?"

In an emailed statement to MedPage Today, the CDC said it would update its breakthrough case and death data in mid-November, to reflect data through October 2.

Why early October? In its statement, CDC said that's because the data are "reported based on when the patient was tested, not the date they died. Deaths usually occur up to 30 days after diagnosis. This is why CDC allows at least 4 weeks of lag time to link case surveillance data to Immunization Information System (IIS) and vital records data up to a month after the diagnosis."

Yet some states report their data on breakthrough cases, hospitalizations, and deaths in real-time, or at least on a more regular basis.

When asked to clarify their reasoning, CDC did not respond.

David Dowdy, MD, an epidemiologist and associate professor at the Johns Hopkins Bloomberg School of Public Health in Baltimore, said CDC likely reasoned that a breakthrough death today reflects a vaccination status and infection from a month ago, as an infection wouldn't lead to immediate death.

But, Dowdy said, "It should still be possible to present cases and hospitalizations by vaccination status, not instantaneously, but without a four-week lag."

Katelyn Jetelina, PhD, MPH, an epidemiologist at UTHealth School of Public Health in Dallas, said that for researchers, following the numbers in real time is crucial, as is having a way to communicate trends to the public.

"Without a national, coordinated surveillance system that's publicly available, both of those are very difficult to do, and we're basically flying blind right now," Jetelina told MedPage Today.

Guided By the States

Given the lack of national numbers, state-level data provide some insights into breakthrough cases, hospitalizations, and deaths.

A July report from the Kaiser Family Foundation found that 15 states were keeping regular tabs on breakthroughs, and more are doing so now.

In states that have seen recent COVID-19 surges, breakthrough numbers can be substantial. In some cases, breakthrough hospitalizations in particular make up a significant proportion of overall hospitalizations.

Colorado, which is facing a surge of infections, updates its breakthrough hospitalization data daily. As of November 9, current hospitalizations tallied 299 in vaccinated people and 1,127 in unvaccinated or not fully vaccinated people -- thus, about 21% of COVID hospitalizations occurred among the vaccinated in that state.

In New Mexico, which is facing a surge in infections, 14.8% of hospitalizations and 19.6% of cases over a 9-month time period (February 1 to November 8) occurred in fully vaccinated people (and thus, proportions could be higher if focused solely on a more recent time period).

And during North Dakota's peak October surge (the week of October 10), 57 fully vaccinated and 156 unvaccinated people were hospitalized that week, with the vaccinated accounting for about 27% of COVID hospitalizations -- albeit the numbers are small.

During that week, 1,141 new cases in the state occurred in fully vaccinated people, compared with 3,172 in the unvaccinated, translating to 26% of new cases being breakthrough cases.

More to Learn About Breakthroughs

Older age and immunocompromised status increase the risk of a breakthrough infection, as evidenced by the CDC criteria for booster eligibility. Yet neither the CDC nor the states whose breakthrough data MedPage Today reviewed provided information about gender, race, and other demographics for breakthrough cases.

However, Alessandro Sette, DrBiolSci, of the La Jolla Institute for Immunology in California, said breakthrough data shouldn't necessarily influence people's decision to get a booster.

Instead, they should get a booster when they become eligible, regardless of the rate of breakthroughs.

"Even if breakthrough infections did not exist, I feel the recommendation would be to get a booster when you need it," Sette told MedPage Today.

Dowdy said it's also important to remember that vaccines still do an excellent job of preventing serious illness and death. He compared getting COVID-19 after vaccination to getting the flu, with some exceptions.

"We have been willing to have holiday celebrations in the midst of flu season from the very beginning of time, for our country at least," he said. "But at the same time, we are dealing with a new disease that we don't have all the long-term data [for], and we don't know if we're going to be seeing a new wave."

Jetelina added that public tracking of breakthrough infections among those with a booster, too, would be useful.

Updated data, she said, would show the value of the vaccines to the still-hesitant, help science communication, and support regulatory decisions on booster shots for a wider swath of the population.

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