Scientists are looking at whether it will be safe to give a COVID-19 vaccine to previously infected individuals, since many of them may not be aware that they had the coronavirus.
Army scientists, the nation’s top clinicians and pharmaceutical researchers working on COVID-19 vaccines also want to know whether vaccinating individuals who have already recovered might boost their natural immunity, helping stave off a potential second infection.
Answering those questions will be critical to determining the effectiveness of a vaccine, the potency of naturally induced antibodies, and whether individuals who want to be vaccinated will require antibody testing beforehand to determine whether they had COVID-19.
According to government estimates, nearly half of all cases could be asymptomatic.
“Can you get a vaccine after you’ve been infected?” Dr. Kayvon Modjarrad, director of emerging infectious diseases at the Walter Reed Army Institute of Research, said in a recent interview with McClatchy. “We’re concerned that if you get infected, you may not have long-term immunity – that you may get reinfected.”
“If you get a vaccine boost after infection, will that give you better protection and longer protection than if you didn’t get a vaccine at all?” Modjarrad continued. “We are going to be looking at that. There are other companies that are going to be looking at that.”
Walter Reed scientists plan to conduct studies in animals — and eventually in people — on the impact of vaccinating those who have been previously infected, Modjarrad said.
That research is already underway with volunteers in Phase III clinical trials being conducted around the country with the leading vaccine candidates.
Dr. Larry Corey, who is co-leading the coronavirus vaccine clinical trials for the COVID-19 Prevention Network under the National Institutes of Health, told McClatchy that the trials have excluded individuals who said they already had COVID-19.
The primary goal of the trials is to get as much data as possible on whether the vaccine is safe and effective for those who have not yet been infected, Corey said. But if the individual did not report having COVID-19 they would continue in the trial.
“If they did not say that, and were found to be seropositive at entrance, they are continued in the trial, as we want to see if the vaccine is safe in people with prior evidence for infection,” Corey said, referring to blood testing that detects the presence of the virus.
Any finding that vaccines are not safe in individuals who have already been infected could create new challenges to the distribution of a vaccine.
Three vaccine candidates produced by Moderna, Pfizer and AstraZeneca are currently in advanced human trials in the United States.
While the Army vaccine candidate being produced at Walter Reed is still in animal testing, Modjarrad said that his team hopes to produce a vaccine and research that addresses any remaining questions or needs after private industry vaccines become available to the public.
“Initially, in our first clinical trial, we want to make sure that the vaccine is generating a strong immune response in those who are naïve to infection,” Modjarrad said in an email after the interview. “But building upon that, we want to see if vaccination even after infection can boost immunity to provide longer-term protection.”
“The immediate goal is to get a vaccine that protects people now,” Modjarrad said. “We need to also be thinking for the long term; that a vaccine protects people for years, not months, without the need for multiple boosters.”