A Maryland county offered antibody tests to all its employees. It says its COVID precautions are working.

Howard County EMT Christina Castro stands in the ambulance bay at the West Friendship Volunteer Fire Department. Castro was among hundreds of county first responders who volunteered for a blood test as part of a state health department study to see if she had antibodies for the virus.

Like many of her colleagues in the Howard County fire department, Christina Castro has worried about whether her job put her family at risk during the coronavirus pandemic.

“The last thing I ever want to do is bring something home from work,” said Castro, a firefighter-paramedic who wondered if she might unknowingly carry the virus to her husband and children after interacting with COVID-19 patients.


So Castro was among hundreds of county first responders who volunteered for a blood test as part of a state health department study to see if she had antibodies for the virus. Castro’s results were negative.

Antibodies are proteins that fight infections. If they are in someone’s blood, that suggests they have been previously infected — even if they showed no symptoms. A negative antibody test does not always mean someone was never infected. It can take one to three weeks after an infection for the body to make antibodies, and some people can take longer or may not develop antibodies, according to the CDC.


Overall results show that less than 2% of the nearly 600 public-safety workers — including police officers, sheriff’s deputies, firefighters and corrections officers — who were tested between late October and early December had antibodies present in their blood, county officials said.

That is lower than the current overall infection rate in the county. Howard County has seen 10,898 confirmed cases of the virus, which represents about 3.3% of its population, according to state health data based on viral testing.

County leaders believe the low rate among emergency workers confirms they are adhering to basic practices — mask-wearing, hand hygiene and social distancing — and that those precautions are working.

When general-government employees were tested for antibodies in early December, the rate was a little higher: Roughly 3.5% of about 300 who participated tested positive.

The tests provide valuable health information on the individual level and also represent a contribution to scientific understanding, said Angela Cabellon, the county’s chief innovation officer and the deputy chief administrative officer.

County Executive Calvin Ball has taken a keen interest in this kind of research — known as serology — saying it will help paint a clearer picture of the true prevalence of the virus and show whether precautions are working to protect public employees. The research could also help scientists better understand how long antibodies last in the population.

In addition to taking part in the state health department study of first responders like Castro, the county offered antibody testing to all its employees through Quest Diagnostics. Ball had his blood drawn at a lab for an antibody test in December, and the results were negative.

Now the county government is working with the Johns Hopkins Applied Physics Laboratory in Laurel to design an even broader antibody study of county residents.


“There’s so much to learn,” said Ball, a Democrat. “We thought that not only could we help improve the safety of our communities, but also add to the body of knowledge. … We might be actually informing people a century from now.”

The Johns Hopkins APL researchers hope to take a deeper look at COVID-19 antibody prevalence among various demographic and occupational groups within the county population, said APL project manager Teresa Colella.

“The reason we’re looking at this is because there are a lot of people who have been asymptomatic carriers,” she said. “They didn’t know that they were ever infected. Or maybe they were sick, they thought it was a cold, and they never got tested for COVID.”

APL is still designing the study and digging into existing data, which include six months of anonymous serology test results from Red Cross blood donations made by county residents.

Firefighter/Paramedic Christina Castro (L)  drawing blood of Lieutenant Amy Breznak as part of the antibody testing done in Howard County.

The county used about $59,000 in federal CARES Act funding for the testing design phase, Cabellon said. County officials hope to secure more federal funding as the project moves forward.

Researchers around the country are examining COVID-19 antibodies in particular communities in hopes of better understanding how the virus has spread through geographic areas and identifying which groups are at highest risk. Other antibody studies have shown that the virus is more widespread than previous COVID-19 testing revealed.


In Houston, for instance, health officials recently found that up to four times as many residents could have been infected than what was indicated by testing. Antibody data there showed that about 13.5% of residents there had been infected by Sept. 19.

In Maryland, a recent Johns Hopkins University study of autopsy reports also suggested that far more residents have been infected with the virus than previously thought. Researchers looked at 500 Maryland autopsy reports from several weeks in May and June and found that 10% had antibodies for COVID-19.

In another study of about 200 firefighters and parademics at a South Florida fire department, researchers found that the prevalence of COVID-19 antibodies was low compared with infections in the wider community. There, 8.9% of the workers tested positive for antibodies, and the community infection rate was double that. Researchers there believe consistent use of PPE and decontamination practices helped protect the employees, despite their frequent exposure to members of the public.

The results from the Howard County employees are limited in that not all employees were tested because the studies were voluntary, said Dr. Matthew Levy, medical director for Howard County Fire and Rescue. But about a third of the county workforce participated, which he said is a good sample size — and the results suggest that the steps the county is taking to prevent the virus from spreading among first responders are working, Levy said.

No individually identifiable data from the tests were made available to the county administration, Levy said.

Lt. Darrin Granger, commander of the administrative services unit for the county sheriff’s office, said he took the test in part out of curiosity.


“I wanted to know and I’m sure a lot of other deputies wanted to find out if they were affected,” said Granger, who tested negative. “My guys are out on the street every single day. Some of them are coming back to the office.”

Granger said the low rate of antibodies gives him confidence that precautions like social distancing and PPE are working to protect employees.

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Because COVID-19 is new, scientists do not yet know how long the antibodies last or how protective they are against the virus, said Dr. Georges Benjamin, executive director of the American Public Health Association and a former Maryland health secretary.

“It doesn’t necessarily mean you’re immune,” Benjamin said. “We’re still telling people you’ve got to wear masks, wash your hands and keep your distance.”

Benjamin said the low antibody rate among county employees “should be reassuring to people that the kinds of thing people are doing to protect themselves” are working. At the same time, “it should reinforce the need for people to get vaccinated.”

Benjamin noted that some of the early COVID-19 antibody tests were “terrible” in terms of accuracy. The ones approved more recently have been more accurate, he said.


“It’s an additional piece of information,” Benjamin said of antibody testing. “It has to be used very carefully, though.”

County officials said they don’t want antibody testing to give anyone a false sense of security. People who tested positive were counseled to continue taking all the normal precautions, like wearing a mask and social distancing, Levy said.

“We will be very honest and transparent in saying, there’s still a lot science is learning,” Levy said.