A recent seroprevalence study of students and teachers in the Colchester School District detected antibodies for the coronavirus in 4.7% of participants.
Benjamin Lee, an associate professor in the pediatrics department at the University of Vermont Larner College of Medicine, one of the study’s co-authors, said the findings were “not unexpected” but nevertheless encouraging.
“This is just one additional piece of data and evidence that to me helps confirm our contention that schools are safe environments,” he said.
Serosurveys use serology tests, which look for the presence of antibodies — proteins made by the body in response to infections.
By testing blood samples for antibodies, serosurveys can detect prior infections, including asymptomatic cases, which make them useful at better detecting the full scope of the virus’ spread in a particular population.
Findings from a recent seroprevalence study from the CDC, for example, suggest that only a sliver of Covid-19 cases in children and adolescents were detected in Mississippi last spring and summer.
Serosurveys of the general population in Vermont predate the state’s second wave, Lee said, while the Colchester survey was conducted in December when cases were surging. That makes it tricky to compare this study’s findings with serosurvey results from the larger community. Still, Lee said mathematical modeling suggests the two — rates within the wide community and within school populations — are not so far apart.
“I think overall, the estimate of just under 5% seroprevalence is really sort of right in line with what the thinking is for the state,” he said.
UVM Medical Center researchers took samples from 532 participants in December, including 336 students and 196 teachers and staff. A follow-up collection is planned for later this year. Funding for the study was provided by the Children’s Miracle Network Hospitals Fund.
A total of 622 participants were enrolled in the Colchester survey. The students enrolled represented slightly less than 20% of the overall district student population.
Antibodies for the virus were detected in 4.6% of samples collected from students, and 4.9% of samples collected from teachers and staff. There was a stark difference in seroprevalence rates detected in students of different ages. Antibodies were detected in only 1.8% of students in grades preK-5. But for students in grades 6-12, that number shot up to 6.9%.
The research has not yet been peer-reviewed or submitted for publication. Without more information about the study’s methodology, and given that testing was volunteer-based and not a randomized sample, experts cautioned about reading too much into its findings. Still, they noted at least one data point was in line with what prior research has found.
Kristen Malecki, an associate professor of population health sciences at the University of Wisconsin, said UVMMC’s findings are consistent with other studies — particularly in Europe, where most school-based serosurveys have been conducted — that show younger kids tend to have lower seroprevalence of the virus.
“That’s about all you can say; I don’t know that you can interpret or extrapolate it any more beyond that,” said Malecki, who has directed a large Covid-19 seroprevalence study estimating infections across the state of Wisconsin.
Anne Sosin, policy fellow at the Nelson A. Rockefeller Center at Dartmouth College, said that the serosurvey’s results echo research elsewhere that suggests very young children are less likely than teens and adults to catch the virus.
But she said she would caution anyone from drawing conclusions about how often within-school transmission occurs based on its findings or how prevalent the virus is in student or teaching populations outside the district.
UVMMC’s research helps us understand “the seroprevalence in that population in Colchester under a defined set of conditions,” she said.
“We can’t, however, generalize it to another community or another set of conditions, and the higher seroprevalence in older children highlights the need for caution,” she added.
