At least 30 million people in the United States – and probably many others whose diseases have never been diagnosed – have so far been infected with the coronavirus. Do these people still need to be vaccinated?
Two new studies answer the question with an emphatic yes.
In fact, the research suggests that just one dose of the vaccine is enough for these people to turbocharge their antibodies and destroy the coronavirus – and even some more contagious variants.
The results of these new studies are consistent with the findings of two others published over the past few weeks. Collectively, the research suggests that people who have had Covid-19 should be vaccinated – but a single dose of the vaccine may be enough.
“I think this is a very strong reason why people who were previously infected with Covid had to get the vaccine,” said Jennifer Gommerman, an immunologist at the University of Toronto who was not involved in the new research.
The immune response of a person to a natural infection is very variable. Most people make large amounts of antibodies that last for many months. However, some people who have had mild or no symptoms of Covid-19 produce few antibodies that drop rapidly to unfathomable levels.
The vaccinations “even the playing field”, said dr. Gommerman said, so that everyone who has recovered from Covid-19 produces enough antibodies to protect against the virus.
The latest study, which has not yet been published in a scientific journal, analyzed blood samples from people who had Covid-19. The findings suggest that their immune systems would have problems with the defense of B.1.351, the coronavirus variant first identified in South Africa.
But the uptake of the Pfizer-BioNTech or Moderna vaccine significantly changed the picture: it boosted the amount of antibodies in their blood a thousandfold – a massive boost, ‘said Andrew T. McGuire, an immunologist at Fred Hutchinson, said. Center for Cancer Research in Seattle, who led the study.
Abundant with antibodies, samples from all participants could not only neutralize B.1.351, but also the coronavirus that caused the SARS epidemic in 2003.
In fact, the antibodies appear to perform better than those in people who have not had Covid and received two doses of vaccine. Several studies have suggested that the Pfizer-BioNTech and Moderna vaccines are approximately five times less effective against the variant.
The researchers found blood samples from ten volunteers in 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 Moderna vaccine.
Blood taken approximately two to three weeks after vaccination showed a significant jump in the amount of antibodies compared to the samples collected before vaccination. The researchers do not yet know how long the increased amount of antibodies will last, but “hopefully they will last a long time,” said Dr. McGuire said.
The researchers also see increases in immune cells that remember and fight the virus, said Dr. McGuire said. “It seems pretty clear that we are increasing their existing immunity,” he said.
In another new study, researchers at the University of New York found that a second dose of the vaccine did not have much benefit at all for people who had Covid-19 – a phenomenon that has also been observed with vaccinations for other viruses.
In the study, most people had been infected with the coronavirus eight or nine months before, but they increased their antibodies by a hundredfold to a thousandfold when they received the first dose of a vaccine. After the second dose, however, the antibody levels did not rise further.
“It is a true proof of the strength of the immunological memory that they are receiving a single dose and have a tremendous increase,” said Dr. Mark J. Mulligan, director of the NYU Langone Vaccine Center and lead author of the study, said.
In some parts of the world, including the United States, a significant minority of the population is already infected, Dr. Mulligan noted. “They definitely need to be vaccinated,” he said.
It is unclear whether the thousand-fold increase in antibody levels recorded in the laboratory will occur in the real environment. Yet research shows that a single shot is enough to significantly increase antibody levels, said Florian Krammer, an immunologist at the Icahn School of Medicine in Mount Sinai, New York.
Dr. Krammer led another of the new studies, which showed that people who had Covid-19 and received one dose of vaccine had worse side effects from the vaccination and that they had more antibodies compared to those who still had not previously infected.
“If you put together all four papers, it provides pretty good information about people who have already had an infection but only need one vaccination,” said Dr. Krammer said.
He and other researchers are trying to convince scientists at the Centers for Disease Control & Prevention to recommend only one dose for those who have recovered from Covid-19.
Ideally, people should be watched after the first shot if their antibody level drops 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 anti-inflammatory bodies observed in the new study can fight the 2003 SARS virus suggests that a single dose of the vaccine may have led the volunteers’ bodies to “neutralize antibodies in general”. – immune molecules capable of carrying a wide range of related viruses, said Dr Burton.
He and other scientists have been researching for decades whether antibodies can be broadly neutralized to tackle multiple versions of HIV simultaneously. HIV mutates faster than any other virus and evades most antibodies quickly.
The new coronavirus mutates much more slowly, but there are now several variants of the virus that appear to be more contagious or to thwart the immune system. The new study could provide clues on how to make a single vaccine that stimulates the production of neutralizing antibodies that can destroy all variants of the coronavirus, Drs. Burton said.
Without such a vaccine, scientists will have to adjust the vaccinations each time the virus changes significantly. “You’re stuck in a kind of Whac-a-Mole approach,” he said. It will probably take many months not to develop and test the type of vaccine against the coronavirus, but ‘this is the long-term way to approach this virus.’