State reveals results of first coronavirus antibody tests

The Rhode Island Department of Health offered an update Friday morning on the results of its first round of coronavirus antibody testing, noting much higher numbers for Hispanic and Black participants.

Dr. Philip Chan, the department’s consultant medical director for the Division of Preparedness, Response, Infectious Disease, and EMS, led the discussion, which centered on serology testing done at five Stop & Shop locations around the state. Serology testing is used to determine if someone is carrying antibodies for a virus.

Chan said that of the 5,000 letters mailed out to random volunteers, the response rate was about 10 to 15 percent, which met the department’s expectations. RIDOH used the Abbott Architect antibody test – which Chan said is considered “very accurate” – and performed the study between May 5-22.

“We don’t know if having antibodies is protective against COVID-19,” Chan said on a Zoom call with reporters Friday. “What antibodies and serology are good for, though, is they tell us on a general level what percent of Rhode Islanders had COVID-19 in the past even if they weren’t tested … We conducted the study because it’s important to know how many people in Rhode Island had COVID-19.”

Chan noted that the experiment yielded an average seroprevalence of 2.2 percent across the state. He said that “based on this community sampling … numbers are still relatively low in Rhode Island.”

“A lot of people think they’ve been infected, but the fact of the matter is Rhode Island has had a robust response,” Chan said. “Testing access has been good in Rhode Island. We do feel like the levels of infection in general have been low but also keeping in mind seroprevalence widely varies … among racial and ethnic groups.”

The study – done in conjunction with several other partners, including Brown University – sported confidence intervals of 99 percent, which Chan said set a “very high degree of standards.” He said the rate for Hispanic/Latino participants was around 8 percent, about 7.4 percent higher than white volunteers. Black participants’ figure was lower at around 5 percent, but Chan said there was less of a sample size. Chan specifically said the figures for Hispanic/Latino participants were “statistically significant.”

He dove deeper on the numbers, explaining that the overall range spanned 1 to 3.9 percent, but there were significant differences among the Hispanic and Black and white communities. The range for Hispanic participants was 3.4 to 15.8 percent, while for Black volunteers it was 0.3 to 18.7 percent. The range for white participants was tighter at 0.1 to 2.4 percent.

“A lot of Rhode Islanders are susceptible to COVID-19. This really again highlights the disparities in Hispanic and African American and Black individuals,” Chan said. “We’re working on plans to improve testing in those communities, a robust approach. We just have to do more. It’s on our radar, we’re working toward it.”

Chan said the health department has been working with local partners to increase testing access and help those who are uninsured or may face transportation issues. He said they are trying to set up more sites within walking distance.

“We’ve also launched a media and communications campaign,” Chan said. “That will be coming out this month and we’re focused on that, ramping up the ability to get communication materials out there … If we don't look for the problem, then we aren't going to find it.”

RIDOH will keep track of those who have for antibodies to see if they experience any coronavirus symptoms and test positive for the virus.

“Whether they test positive PCR-wise in the future is how we’ll determined if someone has immunity,” Chan said. “One thing that will happen in the future is looking at everyone that has positive antibody tests, are they PCR-positive or not.”

He added that RIDOH is “working with our health equity zones” to help the reduce disparities.

Chan said the other notable takeaway of the study is that the state continues to be “vigilant” in combating the virus. He said that the 2.2 seroprevlance rate is “a bit lower than some of would have expected” when the virus hit its peak in Rhode Island at the end of April.

“We have gotten additional funding from the CDC and others, we are looking to enhance our system,” Chan said. “We’re looking to collect data on gender identity and sexual orientation. We want to monitor and look at rates in those populations.”

He also addressed the potential of herd immunity warding off the virus, a possibility that he “wouldn’t count on bringing protection at this point.”

“Herd immunity generally starts to come into play when you have a large majority of a population that has been previously infected,” Chan said. “We’re nowhere near that … It’s why we have to be vigilant and adhere to public health guidance.”