People who have had COVID may need only one dose of vaccine, releasing vaccines

• Some experts believe that people who have taken COVID-19 should only receive an injection of two doses of vaccines against the coronavirus.
• This would provide protection for these people, while releasing doses of vaccine to others, they say.
• However, other experts warn of the approach it can be logistically difficult and scientifically “risky”.
• Visit the Business section of the Insider for more stories.

Experts are divided on whether people who have received COVID-19 need a complete coronavirus vaccine schedule to protect them from reinfection.

Early studies show that these people produce robust immune responses after just one dose of the two-dose COVID-19 vaccines, such as those made by Pfizer and BioNTech, AstraZeneca and Oxford University and Moderna.

Some experts argue that dispensing the second injection for these people would be safe and would release vaccines for others. Indeed, they say that a previous COVID-19 infection could act as the first injection. France made this position its official policy on February 12.

Other experts, including Dr. Anthony Fauci, the United States’ leading infectious disease specialist, said it was too early to make that call – but even he says the results of those early tests are “really impressive”.

More than 115 million people have been infected with COVID-19 worldwide, according to Johns Hopkins University. That figure includes more than 28.8 million people in the United States, more than 4.2 million in the United Kingdom and more than 3.8 million in France.

“If you could save a dose for every person who took COVID-19, it would be a lot of doses,” Lawrence Young, a virologist at the University of Warwick, UK, told Insider.

Fauci, the chief medical advisor to President Joe Biden, told NBC on February 21 that the “boost” of immunity to give a single COVID-19 vaccine to people who had the virus was “huge” and the data was “really impressive. . “

The US government was therefore “looking very carefully” if a dose was sufficient – but it was still too early to make a change, said Fauci.

The Johnson & Johnson COVID-19 vaccine, authorized in the United States in February, requires only one injection.

There is evidence of mounting single-shot protection for those who have had COVID-19

A US study of more than 100 people showed that those previously infected with COVID-19 had an antibody response 10 times greater after one dose of the vaccine than people who were not infected and received two doses.

The study authors, from Mount Sinai, New York, also said that those who had already taken COVID-19 experienced more side effects after immunization – such as a more painful or redder injection site – than those who were not infected. Giving just one dose can lessen these side effects, they said.

The study, published on February 1, was preprinted and has not yet been examined by other experts in a peer review.

Another American group from the Maryland medical school found that healthcare workers who had previously been infected had a 500-fold increase in antibody response since the study began in 14 days after a single injection. “The response was bigger and faster than those without COVID-19,” Mohammad Sajadi, an associate professor of medicine at the University of Maryland’s Institute of Human Virology, told Insider. The study was published in the Journal of the American Medical Association on March 1.

Initial clinical trials did not observe this phenomenon because volunteers at the time probably had not contracted COVID-19 before, explained Sajadi.

A UK-based study of 51 healthcare professionals published in correspondence with the medical journal Lancet on February 25 reported a 140-fold increase in antibody levels in people previously infected with COVID-19 after a dose – more than those who they didn’t get the virus before.

Another UK study of 72 health professionals in London, published in correspondence with the same newspaper on the same day, showed that those who had a previous COVID-19 infection produced 25 times more antibodies against COVID-19 than people who did not. had. previously infected, and their T-cell responses – another crucial part of the immune system – were approximately 10 times greater, 21 days after the first dose.

Mount Sinai researchers said that changing the policy to give individuals who took COVID-19 a dose of the vaccine could release many “urgently needed” doses.

Sajadi also said that this was a solution to the shortage of vaccine supplies that would not consume many resources.

“In the United States, 9% of people have been diagnosed with PCR or antigen tests to release a 4-5% increase in vaccine supply without doing any extra antibody screening,” said Sajadi.

Assuming that the total US vaccine supply was 500 million doses by the end of June, this could therefore release tens of millions of doses.

William Campbell photo / Getty Images

Sajadi said that we still don’t know how long people would be protected after the first injection if they had already had COVID-19, but said there is evidence that antibody responses can last up to nine months. Immunity to other coronaviruses decreases over time.

He said that dispensing the second dose would not work for everyone. People with weakened immune systems or low levels of antibodies after COVID-19 infection – like older people – would be in a different group. This is the case in France.

The authors of the UK study of 75 health professionals, who do not advocate a change in vaccine policy, said their study suggested that those over 50 and not previously infected with COVID-19 had a weaker immune response to a single dose of the vaccine.

Sajadi said it was also unclear what advice would be given to people with “long COVID”, that is, people with symptoms of COVID-19 lasting more than a few weeks, because the single dose approach has not been tested in this group.

I cannot guarantee protection

Other experts are skeptical. “We don’t know what kind of immunity, duration of immunity or potency of immunity that the two-dose vaccine provides, compared to a single dose on top of a previous infection,” Jonathan Ball, professor of Molecular Virology at the University of Nottingham, said. the Insider.

“So while you may argue that it is a way to save a dose of the vaccine, you cannot guarantee that it will be as much protection as someone who receives both.”

Ball said that in terms of “serious side effects”, none of them came to his attention for those previously infected with COVID-19 who received two vaccines.

“Scientifically, it’s not crazy, we don’t have the same amount of data as we have with clinical trials [that tested two doses]”Said Ball.” It would be a courageous decision to introduce this as a sudden policy. ”

Ball said that where there was a serious supply problem, we may need to try new ways to meet demand, such as prioritizing those who did not have COVID-19 for the first few doses, but we must still ensure that everyone receives two doses eventually.

Professor Paul Morgan, director of the Systems Immunity Research Institute at Cardiff University, told Insider that giving just one injection to those who already had COVID-19 was “a good idea, but risky”.

Morgan said that immunity varies between individuals. “Some are better prepared to defend themselves than others,” he said.

Morgan said it would be “laborious, time-consuming and very expensive” to find out who would be eligible for such a scheme.

Young also said that the mass vaccination effort was already a logistical challenge, and changing the approach could delay the vaccine’s launch.

“People will not know whether they had COVID-19 or not, and we would also have to find out how much of an immune response they had,” he said.

It is also unclear whether the science is valid for other, more contagious variants of the coronavirus.

“It changes the equation,” said Sajadi. “The vaccine may play a role in increasing or altering immune responses in people who have had COVID-19, but more data is needed.”