NEW HAVEN — The use of convalescent plasma as a treatment for COVID-19 has yet to show a great deal of promise, though Yale New Haven Health is using it as a treatment in the sickest patients, Dr. Thomas Balcezak, chief clinical officer of the health system, said Monday.

The Food and Drug Administration issued an emergency use authorization for convalescent plasma Sunday.

During an online press conference, responding to reports of people coming down with COVID a second time, Balcezak also said, “Right now, the number of patients that have been demonstrated to be truly reinfected with the virus is vanishingly small.”

Also, the Phase 3 trial of a vaccine, in cooperation with Pfizer, has more than 300 subjects signed up, but more can volunteer, he said.

Plasma, which is taken from people who have recovered from COVID and who have antibodies in their blood, is being used “in every single one of the Yale New Haven Health System hospitals,” Balcezak said. Giving plasma to patients has been part of an expanded-access trial at the Mayo Clinic.

He said patients given convalescent plasma “may have gotten somewhat better from it, although we have seen no spectacular improvement.” He said any benefit is “probably quite mild.”

Balcezak said “one of the challenges” in interpreting the data from the Mayo Clinic study was a lack of a control group. “There was no placebo arm to that trial. … So while there was demonstrated to be a little benefit, it was not a remarkable benefit. And because there was no harm demonstrated … and a little benefit, that’s why they have granted the emergency use authorization. It is no panacea.”

The New York Times reported Monday that a confirmed case of reinfection with the coronavirus had been reported in Hong Kong more than four months after the first infection, suggesting that immunity may last only a matter of months.

“I think the remarkable thing here is how few cases of reinfection have been reported around the world,” Balcezak said.

“And I think while it is only a sporadic case here and there, while millions and millions of people have had this disease, it tends to make me believe that reinfection is extremely rare,” he said.

Balcezak said reports that the amount of antibodies in the blood “falls rapidly after three or four months” has been shown in several studies. But he said little is known about the chances of becoming reinfected. He said as more becomes known it will have “implications potentially for how often we’re going to need to re-vaccinate people.”

In the Pfizer trial, patients will have six follow-up visits to check their antibody levels for two years after being vaccinated. Balcezak also said antibodies are only one way the body can fight reinfection, such as T cell-mediated immunity and memory B cells, which can last for years.

“So it’s possible that you can have a loss of a large number of antibodies but still remain immune, but that still remains to be figured out,” he said.

Balcezak said the vaccine for the Pfizer trial will be arriving soon, possibly this week, but there are challenges, including that the vaccine must be kept at a temperature of 112 degrees below zero Fahrenheit.

The Yale Center for Clinical Investigation is conducting the trial and volunteers may sign up to participate at yalecovidvaccine.org.

Balcezak and Marna Borgstrom, CEO of Yale New Haven Health, said they were encouraged by the continued low rates of cases in the state, with only 24 patients in the system as of Monday. But Balcezak cautioned about growing lax about social distancing, mask wearing and hand washing.

“We’ve seen a little flare-up in Danbury. There have been some additional efforts to try lock down and control crowds in Danbury to try to reduce the spread.”

He called the spike “a cautionary tale” because a spike could occur anywhere.

On Friday, the state Department of Public Health reported that there were at at least 178 new COVID-19 cases in Danbury between Aug. 2–20, up from 40 during the previous two weeks.

“While it’s disappointing and unfortunate that there’s been a spike in cases in Danbury, I think they’re handling it very aggressively and appropriately, and we are going to need to do the same should we see a spike,” Balcezak said.

Borgstrom said there were two fewer cases at Yale New Haven Hospital, totaling 17, and one new case at Greenwich Hospital, which had had no cases the day before. But Balcezak said that patient was a woman coming in to give birth and was found to have COVID-19 because all patients are tested when they are admitted.

“We are admitting people for a condition and it may turn out that they have COVID-19 as well … but they’re not cases that are coming in for care because of the COVID-19; they’re coming in because they have other conditions that require care,” he said. “This disease exists in our communities, whether we recognize it or not.”

On Monday, there were four cases reported at Bridgeport Hospital, one at Lawrence and Memorial Hospital in New London and one at Westerly Hospital in Rhode Island. At its peak, there were more than 800 COVID-positive patients in the health system’s five hospitals.

Connecticut Media Group