A new study in two states that compared coronavirus protection from prior infection and vaccination has concluded that getting the shots is still the safest way to prevent COVID-19.
The study examined infections in New York and California last summer and fall and found that those who were vaccinated and who survived the pre-COVID-19 battles had the most protection.
But unrelated people with previous infections were a close second. By the fall, when the more infectious delta variant had taken over, but boosters were not yet widespread, that group had lower case rates than vaccinated people who had no previous infection.
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The Centers for Disease Control and Prevention, which released the study Wednesday, issued several caveats to the research. And some outside experts were wary of the findings and wary of how they might be interpreted.
“The basic message is that with symptomatic COVID infection you produce some immunity,” said immunologist E. John Vary of the University of Pennsylvania. “But it’s still much safer to get your immunity from infection than it is to get vaccinated.”
Vaccination has long been urged even after a prior case of COVID-19 because both types of protection eventually wear out – and there are too many unknowns to rely only on previous infection, especially From a long time ago, Ali Elebedy, immunologist at the University of Washington, has been added. in St. Louis.
“There are so many variables that you can’t control that you can’t use it as a way of saying, ‘Oh, I’m infected so I’m safe,'” Elebedy said.
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The research comes in line with a small set of studies that found that uninfected people with a previous infection had a lower risk of a COVID-19 diagnosis or disease than those who had never been infected before.
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The new study’s findings make sense, said University of Iowa epidemiologist Christine Peterson. He said a vaccine developed against an earlier form of the coronavirus is likely to be less and less effective against newer, mutated versions.
However, experts said, there are several other potential factors at play, including whether the effectiveness of the vaccine in many people simply fades over time and the extent to which mask-wearing and other behaviors played a role in what happened.
Another thing to consider: Trials for “strongly unconfirmed” are unlikely and the study only included laboratory-confirmed cases, Veri said.
“It could be that we are not picking up as many reinfections in the uninfected group,” he said.
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CDC officials noted other limitations. The study was done before the arrival of the Omicron version and before many Americans received a booster dose, which has been shown to dramatically increase protection by increasing levels of virus-fighting antibodies. The analysis did not include information on the severity of past infections, or the risk of serious illness or death from COVID-19.
The study authors concluded that vaccination “remains the safest strategy” to prevent infection and that “all eligible individuals should be up-to-date with COVID-19 vaccinations.”
Researchers looked at infections in California and New York, which together account for about 18 percent of the US population. He also looked at COVID-19 hospitals in California.
Overall, about 70 percent of adults in each state were vaccinated; The other five percent had been vaccinated and had a previous infection. A little less than 20 percent were not vaccinated; And roughly five percent were not vaccinated but had a previous infection.
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Researchers looked at COVID-19 cases from late May to mid-November last year, and calculated how often new infections occurred in each group. As time went on, vaccine-only protection became less and less effective.
As of early October, compared to unvaccinated people who had not previously had the infection, the case rate was:
– Six times less in California and 4.5 times less in New York among people who were vaccinated but not already infected.
– 29 times less in California and 15 times less in New York among people who were infected but never vaccinated.
– 32.5 times less in California and 20 times less in New York among people who were infected and vaccinated.
But the difference in rates between those last two groups was not statistically significant, the researchers found.
Only hospitalization data from California followed a similar pattern.
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