By Dennis Thompson
HealthDay reporter
THURSDAY, February 11, 2021 (HealthDay News) – If you had suffered from COVID-19 earlier in the pandemic, could one shot of a coronavirus vaccine be enough?
Yes, new research demands.
A couple of new, small studies found that patients previously infected with COVID and given their first dose of vaccine had the kind of robust immune response that people generally have after their second “booster” dose.
“People who have previously had COVID produce antibodies in much higher concentrations very quickly than those who have never had the virus,” said Dr. Viviana Simon, lead researcher in one of the studies and professor of microbiology and infectious diseases at the Icahn School of Medicine at Mount Sinai in New York City.
“That led us to conclude that a second vaccination shouldn’t be required in previously infected people,” said Simon. “That would save vaccine doses and also limit people’s complaints when vaccinated.”
However, given the practical considerations about the pandemic, these results are likely a moot point, other experts said.
The new articles recently published on the medRxiv preprint server must be peer-reviewed and verified through follow-up examinations before a single-shot strategy can be implemented on previously infected individuals. This will take valuable time.
Future studies to see if a single dose of vaccine is enough in a group of people “would take several months to get a meaningful answer,” said Dr. Anthony Fauci, director of the US National Institute for Allergies and Infectious Diseases.
“At this point, the amount of vaccine available would almost make this a moot point,” Fauci said during a meeting of the White House’s COVID-19 Response Team Monday. The current shortage of vaccine supplies is expected to improve as Pfizer and Moderna step up production and other vaccine candidates gain approval from the US Food and Drug Administration.
Measurement of the antibody response
Mount Sinai researchers have been tracking health care workers infected with COVID to see how long a natural antibody response to the novel coronavirus lasts and to see if patients have re-infection, Simon said.
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When the COVID-19 vaccines were launched in December, the researchers expanded their study to see how previously infected people would react to the vaccine.
They found that in 41 people with pre-existing immunity, the antibody response matched or exceeded 68 other people who had never had COVID, the results show.
This strong reaction occurred even in people who had no symptoms of their COVID infection or lower antibody levels prior to the first dose, Simon said.
“This makes sense if we look at the natural infection as the main dose, like the first dose, and then the vaccine is like the surge or second shot for someone who hasn’t seen the natural infection,” Simon said.
Another University of Maryland study recently came to a similar conclusion: 33 previously infected people reacted more strongly to their first shot than 26 others who were never infected.
“I believe there is evidence that someone with a previous COVID infection can achieve adequate immunity with just a single dose of a two-dose vaccine,” said Dr. Amesh Adalja, a senior scientist at the Johns Hopkins Center for Health Security in Baltimore. “Previous immunity from natural infection can be boosted by vaccination for more permanent and robust immunity.”
However, Adalja noted that these small studies need to be verified by larger studies, as does Dr. Andrew Badley, head of the Mayo Clinic’s COVID task force.
“The concept of maintaining vaccine supplies by giving those who have recovered from SARS-CoV2 infection a single dose of vaccine instead of the usual two-dose regimen is a very reasonable idea that can actually be effective,” said Badley, an Infectious Disease Expert. “However, today we do not have enough data to recommend this approach, but personally I would recommend testing it under the heading of a controlled clinical trial.”
B memory cells, which are vital for immunity
Dr. Thad Stappenbeck, Chair of Inflammation and Immunity at the Lerner Research Institute at the Cleveland Clinic, is reluctant to accept the one-shot strategy because higher antibody levels don’t always protect people from serious illness.
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“For me these are really the critical data, right? There are hospital stays and deaths. We are trying to prevent that,” said Stappenbeck.
Clinical studies have shown that two doses are incredibly effective at generating antibodies that can fight off not only the novel coronavirus but also the variants that have emerged in recent weeks, according to Stappenbeck.
Most important to this response are the immune system’s memory B cells, which show that the body learned the lessons from the vaccine, Stappenbeck said. More studies would need to be done to show that a single shot would strengthen immune memory sufficiently in previously infected people.
“While the amount of antibodies is important, these B storage cells are really critical,” said Stappenbeck. “A fine-tuned immune response is the key to longer-term immunity.”
More information
Learn more about COVID-19 vaccines at the U.S. Centers for Disease Control and Prevention.
SOURCES: Dr. med. Viviana Simon, professor of microbiology and infectious diseases at the Icahn School of Medicine at Mount Sinai in New York City; Anthony Fauci, MD, director of the US National Institute of Allergy and Infectious Diseases; Andrew Badley, MD, infectious disease specialist, Mayo Clinic, Rochester, Minn .; Thad Stappenbeck, MD, PhD, Chair of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic
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