CDC Should Track All Breakthrough COVID-19 Cases to Understand Vaccine Effectiveness: Experts

A nurse holds a Pfizer-BioNTech COVID-19 vaccine in Southfield, Mich., on Nov. 5 2021. Jeff Kowalsky/AFP via Getty Images

The Centers for Disease Control and Prevention (CDC) stopped tracking all breakthrough cases of COVID-19—those that occur in people vaccinated against the virus—in May 2021 and has since only tracked breakthrough cases that lead to hospitalization or death.

While the agency has published several studies in the past year as part of an effort to better understand the effectiveness of the COVID-19 vaccines, some critics say that not having a national tally of breakthrough cases is limiting that effort.

“Lack of complete and representative data on breakthrough cases means that it is not possible to estimate the risk of breakthrough cases among vaccinated people,” Dr. Harvey Risch, professor of epidemiology at the Yale School of Public Health, told The Epoch Times in an email.

“[Without the data on breakthroughs,] the benefit of the vaccines for risk of infection cannot be estimated accurately during the Delta and Omicron waves.”

Public health officials including White House chief medical adviser Dr. Anthony Fauci have repeatedly said since the rollout of vaccines that breakthrough cases “are going to happen.” This has been especially apparent since the emergence of the Delta and Omicron coronavirus variants, which are more able to evade immunity.

But the total number of breakthrough cases nationwide isn’t clear, except through examining data in some states that are tracking breakthroughs, despite the logistical challenge of doing so, as it requires matching the vaccine database with the COVID-19 case database.

White House chief medical adviser on COVID-19 Dr. Anthony Fauci listens as President Joe Biden (out of frame) speaks about the 50 million doses of the COVID-19 vaccine shot administered in the United States, in the Eisenhower Executive Office Building, in Washington, on Feb. 25, 2021. Saul Loeb/AFP via Getty Images

“CDC likely determined that they could not do it well, based on a patchwork of differing state reporting practices, thus CDC opted not to do it at all,” Dr. David Boulware, professor of medicine in the University of Minnesota’s Division of Infectious Diseases and International Medicine, told The Epoch Times in an email.

“The Minnesota Department of Health has good data on vaccine breakthrough cases, but it takes them over a month to match up the data and make sure it is correct.”

The Minnesota Department of Health website shows the majority of reported COVID-19 cases to be among people who haven’t been fully vaccinated for the virus.

For the week starting on Dec. 19, 2021, the state agency reported 744 COVID-19 cases per 100,000 of those who aren’t fully vaccinated compared to about 376 per 100,000 of those who are.

For the week of Jan. 10, the state of New York tallied a rate of 996 COVID-19 cases per 100,000 among the unvaccinated, compared to 125 cases per 100,000 among the fully vaccinated.

The state of Delaware also tracks breakthrough cases. Its website states that of the 580,412 fully vaccinated Delawareans, there have been 16,469 breakthrough cases of COVID-19, which is roughly 2.84 percent.

Risch noted that “a large fraction” of new cases have been among vaccinated individuals since the emergence of the Omicron variant, noting that “this is evolving.”

Lawmakers have also pushed at times for the CDC to compile more comprehensive data on breakthrough cases.

Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, testifies on Capitol Hill on Nov. 4, 2021. Elizabeth Frantz/Reuters

The CDC has also relied on state data for many of its studies on vaccine effectiveness.

One study published on Jan. 19 found natural immunity from prior infection offered superior protection compared to vaccines during the surge of the Delta variant cases in the fall. That study analyzed health data from the California and New York public health departments.

Another study published on Jan. 21 regarding the waning efficacy of primary series vaccines and the effectiveness of a third vaccine booster dose looked at emergency department and urgent care encounter data in 10 different states. It found that primary series vaccination effectiveness drops off significantly after six months and that a booster dose restores protection to more than 94 percent for Delta and 82 percent for Omicron.

In an interview with NPR in August, Director of the Yale Institute for Global Health Saad Omer said that “a random sample can be helpful,” but noted that to get ahead of an outbreak, you have to make sure that you’re not just testing severe cases.

“From my perspective and some other experts’ perspective, it is not insufficient to give us an early, complete, robust picture of things that we are not expecting,” Omer said. “It’s the unknown unknowns that get us.”

The CDC uses COVID-NET to track breakthrough hospitalizations. COVID-NET is described on the agency’s website as a “population-based surveillance system that collects data on laboratory-confirmed COVID-19-associated hospitalizations among children and adults through a network of over 250 acute-care hospitals in 14 states.”

Data from COVID-NET is posted on the CDC’s COVID-19 data tracker website and has shown that people who are unvaccinated are more likely to be hospitalized with COVID-19.

Also, World Health Organization head Tedros Adhanom Ghebreyesus warned on Jan. 24 against assuming that Omicron is the last variant of the virus that causes COVID-19, saying that conditions are ripe for more strains to appear.

The CDC didn’t respond to multiple requests for comment. The agency continues to recommend COVID-19 vaccines and booster shots for all eligible populations.