Olmsted County’s spike in COVID-19 cases and emerging vaccinations serve as bookends to an effort to gather more information about how the virus is spreading in the community.

Mayo Clinic researchers have partnered with the county, city of Rochester and others to determine how many people might have been walking around with the virus and not known it.

“We are actually in a good time to be conducting this study and recruiting people,” said Jennifer St. Sauver, a Mayo Clinic epidemiologist and co-principal investigator with the Rochester Epidemiology Project.


Newsletter signup for email alerts

The study aims to test approximately 700 people who are at greater-than-average risk of being exposed to COVID-19 to determine whether they have developed antibodies to the virus without knowing it.

The current focus is on county staff with public-facing jobs, city police officers and firefighters and private daycare providers.

“I think we are going to get a good span of people working in the community,” said Celine Vachon, chairwoman of Mayo Clinic’s Division of Epidemiology.

County staff members, from front-desk workers and county deputies to people working behind the scenes, have a variety of exposure levels, she said. While the results will be tracked without identifying individuals, they will be able to show how the virus might move differently between daycare workers, public safety staff or general county staff.

Dan Jensen, the operations chief for Olmsted County’s COVID-19 response, said 230 people have been tested so far, with four more testing events planned.

A sample is tested for antibodies in a Mayo Clinic lab. (contributed photo)
A sample is tested for antibodies in a Mayo Clinic lab. (contributed photo)

He said the testing, which involves a fingerstick, was originally scheduled to start earlier but ended up being delayed after the local spike in COVID-19 cases began to emerge.

St. Sauver said the delay means there are likely more people in the test group who have been caught COVID-19, even if they haven’t shown symptoms, adding a layer of interest to the study.

“Not only do we get to understand what has happened with this recent spike that we had, but also there will be enough people that were studied who have had these antibodies,” she said.

How long the antibodies stay in a person’s bloodstream remains uncertain.

“A lot of studies are showing antibodies do decline after three to four months after natural infection, although there is other data suggesting that different types of tests show individuals might be positive for antibodies longer,” said Elitza Theel, who directs Mayo Clinic’s Infectious Diseases Serology Lab.

That means catching people with recently developed antibodies also offers a chance for more insight, since participants have agreed to follow-up testing in some cases.

Some people being tested might have known they had contracted the virus, but St. Sauver said the majority being tested, which includes families of county staff for added insights, haven’t had confirmed cases, so researchers are also asking participants questions about symptoms linked to COVID.

“We can’t really get at them in any other way than by directly asking people if they have ever had symptoms and then by actually measuring whether they have antibodies to the virus,” St. Sauver said.

Vachon said the current study will add to the understanding of how the virus is spreading locally. Mayo Clinic tested health care professionals last year, and the plan is to seek members of the public for future testing.

Regardless of the results, Theel warned that vaccinations are still recommended for lasting immunity.

“Even if you test antibody positive in this study or any other study, that shouldn’t preclude you from getting the vaccine,” she said.

St. Sauver agreed. “We just don’t understand a lot about immunity to this particular disease, so we don’t understand how long immunity lasts among people who were naturally infected,” she said.

Vachon said it also means that masking and adhering to other public health measures remain important until there is a better understanding of how the virus is spreading and how well it can be controlled.

“We really don’t understand in Minnesota how much asymptomatic spread there has been,” she said.