COVID-19 Antibodies In Conn. Residents, Health Workers Give Clues To The True Spread Of The Virus | Connecticut Public Radio
WNPR

COVID-19 Antibodies In Conn. Residents, Health Workers Give Clues To The True Spread Of The Virus

Aug 14, 2020

At least two Connecticut studies and a federal report show that the percentage of health care workers and residents in the overall population who have been previously infected with COVID-19 remains small, despite ongoing cases and hospitalizations.

And the numbers don’t come close to achieving herd immunity, when disease transmission is minimal because most people in a community are protected after vaccination or previous infection. 

Health researchers say the results are likely a testament to how well social distancing and other prevention strategies have been working in the state. But Dr. Harlan Krumholz said they also indicate just how vulnerable the population remains to widespread infection.

“The vast majority of people in the state remain susceptible, and the vast majority of people in the state likely do not have immunity,” he said. “We’re not out of the woods.”

Krumholz, a Yale cardiologist and director of the Yale New Haven Hospital Center for Outcomes, Research and Evaluation, is a lead author of a Yale study recently published in collaboration with Gallup, an analytics firm that conducts polling worldwide, Quest Diagnostics, and the Jackson Laboratory for Genomic Medicine.

Using Gallup’s polling methods, researchers analyzed survey data and blood samples from a random selection of 505 adults who lived in Connecticut between March 1 and June 1. They looked for the presence of COVID-19 antibodies, which are proteins that form after an initial infection and help fight off future exposures.

Based on the study’s results, Krumholz and his team estimate that only 3.1% of the state’s general population have these antibodies and have survived a bout of the virus, whether or not they ever had any symptoms.

But many questions remain about the significance of these antibodies.

“We’re not even sure that people with antibodies are protected [against future infection]. But it is some indication of how far the virus has spread in the state,” he said.

Scientists still don’t know how long COVID-19 antibodies stay in the body, and what level of immunity they have against additional exposures. A lack of answers is why the World Health Organization has come out against the idea of “immunity passports,” or a designation for people with antibodies to travel and return to work “risk-free.”

That’s why Krumholz said studies that follow people and populations over time, rather than snapshots, can better guide public health decisions.

“They’re more useful if we can then accumulate some perspective over time -- the degree to which it’s [the pandemic] growing, and who is starting to develop antibodies, who’s losing antibodies,” he said. “And then we have to understand what that means. So, we’re still unfortunately too ignorant about this virus and so many aspects of it.”

The U.S. Centers for Disease Control and Prevention is conducting ongoing antibody, or seroprevalence, studies in specific cities, regions and states, including Connecticut.

The federal agency has partnered with commercial laboratories to test “de-identified clinical blood specimens” from people who had lab tests ordered for reasons unrelated to COVID-19, like for routine bloodwork or because of sickness.   

The CDC estimates that about 5.2% of Connecticut’s population had COVID-19 antibodies in May, more than four times the number of positive diagnostic cases recorded by the state at the time.

It’s slightly higher than Yale’s estimation, but accounting for margins of error, Krumholz said they’re similar enough.  

In an ongoing study, Hartford HealthCare is testing its employees for antibodies to determine how many of its health care workers and other personnel had been infected with COVID-19 since early March. Early results show that 6.6% of 6,000 employees have antibodies for the virus.

“It included people who did not know that they had contact with the virus, they were completely asymptomatic, and they were surprised that they had antibodies,” said Dr. Pavlos Papasavas, principal investigator of the study.

“It also included people who were very sure that they had the virus because anecdotally they said, ‘I had the symptoms and I’m 100 percent sure I’m going to have the antibodies,’ and they were surprised not to have them [antibodies].”

Health care workers are more likely to come in contact with people infected with COVID-19, especially those working in Connecticut hospitals over the last several months. Papasavas said the use of personal protective equipment and strict disease mitigation protocols likely played a big role in keeping transmission down.

“We started using PPE early, and these results are a testament that the PPE really protect our employees and our patients,” he said. “This is why we don’t see twice the rate in our health care employees compared to the public.”

Papasavas said the health system will continue to test more employees for antibodies. His research team also plans to test this first group of workers again around November to get more information on the longevity of these antibodies.

Health experts say until a vaccine is available and widely distributed, and scientists know more about the virus, people should do what they can to avoid contracting COVID-19, or spreading it to others.

“In the end, it’s going to be about us making smart and wise choices,” said Krumholz, “having some idea about what’s going on, and then some educated guesses, because no one has all the answers.”