Less than a third of Vermonters have ever gotten Covid, CDC study shows

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Vermont has had one of the highest Covid-19 case rates in the nation for nearly two months, according to The New York Times, as the highly infectious BA.2 subvariant swept through the state beginning in mid-March. 

So why would Vermont, with at least two-thirds of its population fully vaccinated and famous for low infection rates at the pandemic’s start, be the center of the nation’s latest surge? 

At a recent press conference, Health Commissioner Mark Levine said the reasons were “multifactorial.” But he pinpointed a seemingly paradoxical factor: the fact that so few Vermonters have gotten sick over the past two years of the pandemic.

“Because we continue to be a state with perhaps still the lowest rate of immunity from having had Covid, we do expect the virus to continue to spread,” he said.

Between a quarter and a third of Vermonters had contracted Covid between March 2020 and February 2022, according to new data from the U.S. Centers for Disease Control and Prevention. That’s compared to nearly 60% of the nation as a whole.

The CDC study measured the percentage of people with an antibody in their blood that only occurs through natural immunity — that is, immunity acquired by getting infected with Covid. 

The study’s wide margin of error makes it hard to say exactly where Vermont ranks nationwide, but it is clearly in the minority. Only eight other states also reported that less than half of their population had been infected with Covid since the pandemic began.

On a national level, the Omicron variant caused a sweeping rise in the likelihood of people being infected, raising the number of Americans with antibodies from about 43% to 58% in the course of a single month. 

Vermont, too, reported a rise, but starting from a lower baseline: It jumped from about 18% pre-Omicron to 29% by late February.

Laura Ann Nicolai, deputy epidemiologist at the Vermont Department of Health, said the rise in immunity during Omicron “matches up well” with what state officials had observed. 

“We were seeing exponentially higher daily case counts during that timeframe,” she said. 

The CDC study also estimated how many infections Vermont has had over the course of the pandemic based on its blood samples. Antibody samples showed the state totaled an estimated 180,000 infections — nearly double the 98,000 the health department had reported based on test results when the study was conducted.

“It doesn't really surprise me,” Nicolai said of the disparity. “We think that there were probably a lot of kids who had mild illnesses and who may never have been tested.”

The state also increased access to “home-based testing opportunities” like antigen and LAMP tests, she said, and “people aren't necessarily taking the extra step to report that” to the health department website.

The CDC didn’t release detailed age data for Vermont, but national data shows that people 17 and younger were the most likely to have gotten Covid during the pandemic, while people 65 and older were least likely.

Benjamin Lee, a pediatric disease physician at the University of Vermont Medical Center, researched the rate of Covid antibodies in children in early 2021.

His research found that, as of December 2020, less than 5% of children in the Colchester school district  had gotten Covid. During Delta and Omicron, Lee said last week, state data shows “the proportion of children who represent the total caseload has gone up a lot.”

That’s partly because the Omicron variant was so infectious, and children have the lowest vaccination rate in the state.

“We had lots of kids who still unfortunately hadn't been vaccinated, even though there were many who are age eligible,” he said. “And many kids that hadn't been infected before now (were) meeting the most infectious variants of the virus that we've encountered at a time when a lot of restrictions were being sort of scaled back.”

He said the low rate of Covid among Vermonters overall could likely be traced to two causes: the high vaccination rate statewide, and Vermonters’ willingness to follow public health guidance on masking, quarantining and social distancing.

About 88% of Vermonters 5 and older have at least one dose of the Covid vaccine, and 59% are up to date on all vaccinations, including any necessary booster doses, according to the health department.

According to Lee, although vaccine-related protection against contracting the virus wanes over time, and the vaccine has gotten less effective against different variants, the vaccine may have played a role in Covid rates remaining low in Vermont in 2021.

Vermonters also mostly followed pre-vaccination guidance to prevent illness, according to a survey from UVM researchers conducted from January to April 2021. The majority of respondents said they always followed guidance about wearing a mask, staying at home and quarantining.

“Our results indicate that Vermonters had a high level of trust in and compliance with public health recommendations from the beginning of the pandemic,” Christine Vatovec, one of the authors of the study, said via email.

Are the 70% of Vermonters who have never gotten infected still destined to get Covid? Levine has often quoted Anthony Fauci, chief medical advisor to President Biden, that the question was “not if, but when.”

Nicolai said Vermonters couldn’t expect to “interact in society and never get exposed,” but said they shouldn’t be disheartened by that news.

“The vaccine is still protecting you from a serious illness,” she said. “It's shortening your duration of illness and most likely shortening the timeframe that you are infectious to others as well.”

Asked if he would have traded Vermont’s low infection rates early in the pandemic and let more Vermonters get infected to prevent the current surge, Levine said he would “never take that away.”

“We had that early success before there was even a hint of a vaccine that would ever be available,” he said. “We were really focused on saving lives and keeping people as well as possible during that time.”

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Erin Petenko

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