Nearly 30 million people in the United States – and probably many others whose illnesses have never been diagnosed – have been infected with the coronavirus so far. Should these people still be vaccinated?
Two new studies answer this question with an emphatic yes.
In fact, research suggests that for these people, just one dose of the vaccine is enough to boost their antibodies and destroy the coronavirus – and even some of the more infectious variants.
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The results of these new studies are consistent with the findings of two others published in recent weeks. Taken together, the research suggests that people who took COVID-19 should be immunized – but a single dose of the vaccine may be sufficient.
“I think it is a very strong reason to explain why people who were previously infected with COVID should receive the vaccine,” said Jennifer Gommerman, an immunologist at the University of Toronto who was not involved in the new research.
A person’s immune response to a natural infection is highly variable. Most people produce large amounts of antibodies that persist for many months. But some people who had mild symptoms or no symptoms of COVID-19 produce few antibodies, which fall quickly to undetectable levels.
Vaccines “up to the playing field,” said Gommerman, so that anyone who has recovered from COVID-19 will produce enough antibodies to protect themselves against the virus.
The latest study, which has not yet been published in a scientific journal, looked at blood samples from people who had COVID-19. The findings suggested that their immune systems would have trouble defending themselves against B1351, the coronavirus variant first identified in South Africa.
But an injection of the Pfizer-BioNTech or Moderna vaccine significantly changed the picture: it amplified the amount of antibodies in your blood a thousand times – “a huge boost,” said Andrew T. McGuire, an immunologist at Fred Hutchinson Cancer Research Center in Seattle, who led the study.
Full of antibodies, samples from all participants were able to neutralize not only B1351, but also the coronavirus that caused the severe acute respiratory syndrome, or SARS, epidemic in 2003.
In fact, the antibodies appeared to perform better than those in people who did not have COVID and received two doses of a vaccine. Several studies have suggested that the Pfizer-BioNTech and Moderna vaccines are about five times less effective against the variant.
The researchers obtained blood samples from 10 volunteers from the Seattle COVID Cohort Study, who were vaccinated months after contracting the coronavirus. Seven of the participants received the Pfizer-BioNTech vaccine and three received the Modern vaccine.
Blood drawn about two to three weeks after vaccination showed a significant jump in antibody amounts compared to samples collected before vaccination. Researchers still do not know how long the increase in antibodies will persist, but “hopefully, they will last a long time,” said McGuire.
The researchers also observed increases in immune cells that resemble and fight the virus, said McGuire. “It seems very clear that we are increasing your pre-existing immunity,” he said.
In another new study, researchers at New York University found that a second dose of the vaccine did not bring much benefit to people who had COVID-19 – a phenomenon that has also been seen with vaccines for other viruses.
In that study, most people had been infected with the coronavirus eight or nine months earlier, but they saw their antibodies rise a hundred to a thousand times when they received the first dose of a vaccine. After the second dose, however, the antibody levels did not increase any more.
“It is real proof of the strength of immune memory that they receive a single dose and have a large increase,” said Dr. Mark J. Mulligan, director of the NYU Langone Vaccine Center and lead author of the study.
In some parts of the world, including the United States, a significant minority of the population has already been infected, Mulligan noted. “They should definitely be vaccinated,” he said.
It is unclear whether the 1,000-fold increase in antibody levels recorded in the laboratory will occur in real-life environments. Still, research shows that a single injection is enough to significantly increase antibody levels, said Florian Krammer, an immunologist at the Icahn School of Medicine at Mount Sinai in New York.
Krammer led another of the new studies, which showed that people who took COVID-19 and received a dose of a vaccine had more serious side effects from the inoculation and had more antibodies compared to those who had not been infected before.
“If you put all four documents together, it will provide very good information about people who have already had an infection and just need a vaccination,” said Krammer.
He and other researchers are trying to persuade scientists at the Centers for Disease Control and Prevention to recommend only one dose for those who have recovered from COVID-19.
Ideally, these people should be monitored after the first injection, in case their antibody levels plummet after a few weeks or months, said Dennis R. Burton, an immunologist at the Scripps Research Institute in La Jolla, California.
The fact that the supercharged antibodies seen in the new study may fight the 2003 SARS virus suggests that a single dose of the vaccine may have caused volunteers’ bodies to produce “widely neutralizing antibodies” – immune molecules capable of attacking a wide range of viruses said Burton.
He and other scientists have investigated for decades whether widely neutralizing antibodies can fight multiple versions of HIV at once. HIV mutates faster than any other virus and quickly avoids most antibodies.
The new coronavirus mutates much more slowly, but there are now several variants of the virus that appear to have evolved to be more contagious or to hinder the immune system. The new study may provide clues on how to make a single vaccine that stimulates the production of widely neutralizing antibodies that can destroy all variants of the coronavirus, said Burton.
Without this vaccine, scientists will need to adjust vaccines whenever the virus changes significantly. “You are stuck in a Whac-a-Mole approach,” he said. It will probably take many months, if not more, to develop and test this type of vaccine against coronavirus, but “this is the long-term way of approaching this virus”.
This article was originally published in The New York Times.
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