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Health district: At least 25% of local COVID-19 cases since July 1 were among the fully vaccinated

‘Breakthrough’ cases are rising amid the spread of the Delta variant

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Local “breakthrough” cases of COVID-19 are much more prevalent than initially anticipated -- likely due the rise in the Delta variant, according to an analysis of COVID-19 cases reported between July 1-17 conducted by the Prince William Health District. 

Of the 233 new COVID-19 cases reported in the health district during the first three weeks of July, between 56 to 66 of them -- or about 25 to 30% -- involved people who were fully vaccinated against COVID-19, said Sean Morris, a COVID-19 epidemiologist with the Prince William Health District.

The numbers were first reported by WUSA9 news reporter Jess Arnold on Wednesday, July 28, and are vastly different from what the Virginia Health Department is still reporting on its website regarding the prevalence of COVID-19 cases among fully vaccinated Virginians.

As of Sunday, Aug. 1, VDH’s “COVID-19 cases by vaccination status” web page showed only 19 breakthrough cases among a total 2,686 COVID-19 cases reported across Northern Virginia since July 1. That data suggests that more than 99% of the cases since July 1 were among unvaccinated residents, which was not true in the Prince William Health District according to the new analysis.

The VDH website lists cases by vaccination status only by region – not by individual health districts.

Morris said the discrepancy has to do with the time it takes to fully analyze and report cases to the VDH, which then conducts its own review. 

“Our specific breakthrough case numbers are not posted until they are sent to the state for further review and posting,” Morris said in a July 30 email.

Morris further pointed to a statement on the VDH website that notes that each breakthrough case is reviewed by a “subject matter expert” and matched to the state’s vaccination records kept through the Virginia Immunization Information System.

“This takes extra time and may delay reporting of cases on this dashboard," the VDH website says. 

 “This may help to explain discrepancies between our data and what is posted as they conduct further quality assurance on them,”  Morris said.

The number of breakthrough cases in the Prince William Health District, which includes the county, Manassas and Manassas Park, was not available earlier this week, the health district’s Community Engagement Director Sean Johnson told the Prince William Times on Tuesday, July 27.

Given the rise of the Delta variant, which is at least twice as contagious as the original strain of coronavirus, the rise in breakthrough cases is not unexpected and is in line with what epidemiologists are reporting around the country, Morris said.

Morris also said the data underscores the need for people who are not yet vaccinated to get vaccinated as soon as possible.

“Breakthrough cases are expected as spread increases, and [the Prince William Health District] appears to be in line with national trends,” Morris said. “And with the growth of the Delta variant and a rise in cases, it is vital to get vaccinated now.”

“Even if you get COVID after being vaccinated, the vaccine gives your immune system a head start to fighting it, resulting in an extremely low chance you'll have severe disease,” he added.

Cape Cod outbreak

Indeed, recent COVID-19 outbreaks in and around the Cape Cod beach town of Provincetown, Massachusetts, prompted the Centers for Disease Control and Prevention to change its mask guidance last week. On Friday, the CDC released its report of the analyses of the outbreaks. In all, they involved more than 900 cases that were traced to gatherings in around the July 4 holiday weekend. 

About three-quarters of those infected were fully vaccinated, but few had severe cases. A total of seven people were hospitalized and no deaths were reported.

The CDC report said the cases indicate the Delta variant is highly contagious and that vaccinated people can become infected with the variant and can spread it to others. Importantly, samples from vaccinated people showed they were carrying about the same amount of virus as unvaccinated people, the CDC report said. 

The CDC is now recommending that both vaccinated and unvaccinated people in areas with “substantial” or “high” community transmission of the virus return to wearing face masks in indoor public spaces and even outdoors in crowded settings.

The CDC investigation also suggests that jurisdictions without substantial or high COVID-19 transmission rates “consider expanding prevention strategies, including masking in indoor public settings regardless of vaccination status, given the potential risk of infection during attendance at large public gatherings that include travelers from many areas with differing levels of transmission,” the report says.

Prince William County has been in the “substantial” range for community transmission of the coronavirus since at least Wednesday, July 28, with more than 56 cases per 100,000 residents over the last seven days, according to the VDH. 

Both the cities of Manassas and Manassas Park are in the “moderate” range of transmission, according to VDH data.

Further prevention steps urged

Morris said the new information about the spread of the Delta variant among both the vaccinated and unvaccinated underscores the importance not only of vaccinations but also testing for those who have symptoms of COVID-19 – regardless of their vaccination status.

“Going into the fall where we are seeing a rise in cases, it is vital we all take steps to protect ourselves from COVID and ensure we are working to limit spread and prevent future surges by getting vaccinated, staying home and seeking testing if you feel ill, and following VDH recommendations,” Morris said.

Most cases among the vaccinated are not severe

Almost all breakthrough cases that occur across the nation are either asymptomatic or mild, and hospitalization and deaths in vaccinated individuals are extremely rare, “which is a trend we see in PWHD as well,” Morris said.

Nationally, about 99.5% of deaths associated with COVID-19 since the vaccine rollout have been among the unvaccinated, according to the CDC, and a Yale study has found that vaccination has prevented up to 279,000 COVID deaths nationwide and 1.25 million hospitalizations, Morris said.

The CDC also found a seven-fold reduction in the likelihood of becoming hospitalized after vaccination, and a 20-fold reduction in the risk of hospitalization or death, Morris said.

“While we are all disappointed in the COVID trends we are seeing, the good news is that now we have the tools and knowledge we need to protect ourselves and turn the corner on it,” Morris said.

Reach Jill Palermo at

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