The Centers for Disease Control and Prevention has changed how it’s tracking breakthrough cases of covid-19—infections in people vaccinated against the viral illness. The changes are said to reflect the astounding success these vaccines have had in preventing serious harm from covid-19, yet some public health experts are worried that the CDC is being too hasty in its decision.
Earlier this month, the CDC quietly announced a change in its monitoring of breakthrough covid-19 cases. As of May 1, it would no longer try to track all reported cases of breakthrough infections in the U.S.; instead, it will now focus on the most serious cases of covid-19 among vaccinated people, which will typically involve hospitalization or death.
“This shift will help maximize the quality of the data collected on cases of greatest clinical and public health importance,” the agency wrote on its page announcing the change.
The change follows a recent report released by the CDC this week on the first 10,000 breakthrough cases reported to the CDC by state and local health departments between January 1 to April 30, 2021. Among these cases, 27% were asymptomatic; 10% involved people who were later hospitalized; and 2% involved people who later died, though not necessarily because of their covid-19 infection.
The report found that these breakthrough cases only occur in “a small fraction of all vaccinated persons and account for a small percentage of all COVID-19 cases.” Moreover, it concluded that “the number of covid-19 cases, hospitalizations, and deaths that will be prevented among vaccinated persons will far exceed the number of vaccine breakthrough cases.”
Research from other countries with high vaccination rates has shown that breakthrough infections are very rare. Some studies have also suggested that these cases should rarely lead to more transmission of covid-19 to other people. Yet at least some public health experts are critical of the CDC’s choice to limit its tracking of breakthrough infections, arguing that more remains to be learned by maintaining a wide net of surveillance. Some fear, for instance, that the CDC won’t be able to spot possible future risks related to the pandemic as easily, such as the evolution of virus variants that significantly evade vaccine-provided immunity (so far, that hasn’t happened).
“We are driving blind, and we will miss a lot of signals,” Ali Mokdad, an epidemiologist at the University of Washington and former CDC scientist told the New York Times Tuesday.
The CDC is conducting more extensive tracking of some vaccinated people, but only in select populations, such as health care workers, according to the Times. Local and state departments also make their own decisions in how to monitor these cases and can still report that data to the CDC, while other countries will have their own systems for tracking breakthrough infections. So it’s likely that there will still be large datasets available for researchers to use in studying the evolution of the virus moving forward.
For the average fully vaccinated person, it remains true that your odds of catching covid-19 are now very low, and will get even lower as the pandemic continues to decline in the U.S and elsewhere. Essentially, though, the CDC is taking a calculated gamble here, betting that it can use fewer resources to track these infections and still reliably keep an eye on any potential surprises the coronavirus has left up its sleeves. Time will tell whether they’re right.