Virginia’s breakthrough case numbers are likely an undercount
Issues with data reporting made it difficult to report and verify cases among vaccinated people
Earlier this week, the Virginia Department of Health updated its public reporting on breakthrough COVID-19 cases to “more accurately represent the impact of vaccinations on infection rates in the commonwealth,” according to a release from the agency.
As the Mercury reported, the data illustrates the higher risk for infection, hospitalization and death among unvaccinated Virginians. But the way it’s presented makes it tough to calculate the prevalence of breakthrough infections in the weeks since the Delta variant began to account for the vast majority of cases across the country.
In other words, VDH isn’t reporting the percentage of breakthrough cases out of all total known infections week-by-week. That makes it hard to know exactly how many of those cases are occurring among immunized Virginians amid the rise of a highly infectious variant that’s been shown to reduce the effectiveness of available vaccines.
Even without that data, though, recent state reporting has seemed to suggest that Virginia’s breakthrough infection numbers are curiously lower than other states — and even localities within the commonwealth. Before VDH changed its dashboard, the department was reporting that less than two percent of all reported COVID-19 cases between January and early August were among vaccinated Virginians. At the same time, some local health departments were reporting numbers that would ostensibly drive up that total.
Prince William, for example, announced that between 25 to 30 percent of its recorded cases throughout the first half of July were breakthroughs.
“And I don’t think Prince William is an outlier,” District Epidemiologist Sean Morris told the Mercury. But even national reporting has described Virginia as strangely immune to infections among vaccinated residents. Last week, The New York Times reported that data from seven states — including Virginia — reflected a rise in breakthrough cases. Virginia was the “outlier” of the bunch with 6.4 percent of its recorded infections among the fully vaccinated. In the other six states, they accounted for 18 to 28 percent of total cases in recent weeks.
It turns out the discrepancy has less to do with Virginia’s good luck and more to do with a likely undercount of breakthrough cases. And VDH officials say that determining the actual prevalence of breakthrough cases from week to week is “discouraged.”
The Virginia Mercury is a new, nonpartisan, nonprofit news organization covering Virginia government and policy.
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