By Annika Kim Constantine -
CNBC
According to a recent study,
having contracted COVID-19 before receiving the vaccine weakens people's immune responses to vaccines against the virus
, which could leave some vaccinated individuals less protected against a new infection.
People who had COVID-19 before being vaccinated have a weaker immune response than those who never had the virus, potentially leaving them less protected against another infection, the research revealed.
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The study, co-sponsored by the National Institutes of Health, casts doubt on other research findings suggesting that prior COVID-19 infection increases the immune response of vaccinated people, a phenomenon known as hybrid immunity , which
some
scientists they believe it provides the best protection against another infection.
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Researchers at Stanford University looked at how immune cells in the blood, called CD4+ T and CD8+ T, responded to a COVID-19 infection and to vaccines.
Those cells work together to produce a response that helps fight off the virus, also killing other cells that have been infected.
The study found that vaccinated people who had never been infected with COVID-19 produced a more "robust" CD4+ and CD8+ cell response to the virus.
Vaccinating these people also generated molecules that send signals to cells and recruit other immune system cells to help in the battle against COVID-19, they explained.
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In contrast, the researchers said that vaccinated people who had previous COVID-19 infections produced a "considerably lower" cell response with "less function."
Unvaccinated people who contracted the infection had even lower levels of CD8+ cells, they noted.
According to a recent study, having contracted COVID-19 before receiving the vaccine weakens people's immune responses to vaccines against the virus.Getty Images
The researchers said these results suggest that COVID-19 infections impair an important immune cell response that is crucial to fighting the virus, which could leave vaccinated people with previous infections less protected.
"The apparent damage to the CD8+ T cell response to viral infection
is cause for concern and may leave people vaccinated but with prior infections at risk
of subsequent infection or other health problems," the study authors stated.
They cautioned that the results underscore the need to develop new vaccine strategies that specifically boost CD8+ T cell responses in people previously infected with COVID-19.
Researchers suggest that COVID-19 impairs an important immune cell response, crucial to fighting the virus
Dr. Stuart Ray, a professor of medicine at Johns Hopkins University, said the study is surprising in that it calls into question what we know about hybrid immunity.
Ray said the results may stem from the way the study was designed, specifically pointing to the fact that the researchers looked at immune cells in the blood, but not in the tissues.
"The cells in the blood are not an absolute measure of everything in the body. The cells that we know protect us are also in the tissues," he told CNBC.
"It's like when you're looking under the lamp for something, when it's in the next field. Maybe you're not looking at all the cells we care about."
Ray said the study, while interesting, needs to take into account long-term insights into how immunity to COVID-19 works: "It's probably not the last chapter in our story," he said.
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The study comes as researchers continue to unravel the impact of COVID-19 on people, even after they recover from the virus,
which has infected more than 100 million in the United States
since the start of the pandemic alone.
The nation continues to have nearly 150,000 new cases each week, according to the Centers for Disease Control and Prevention.
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The new research also comes as
public health officials are considering new COVID-19 vaccines that could reduce the number of doses per year
, or require drugmakers to periodically update vaccines to combat new variants of the virus.
Nearly 81% of the US population is vaccinated with at least one vaccine, while about 70% have completed the primary series of doses, according to the Centers for Disease Control and Prevention.