Is immunity from previous COVID-19 infection or vaccination strongest?There are some tips for new research

New studies in two states comparing coronavirus protection from previous infections and vaccination conclude that taking shots is still the safest way to prevent. COVID-19 (new coronavirus infection.

The study investigated infectious diseases in New York and California last summer and fall and found that those who were vaccinated and survived previous COVID-19 attacks were the most protected.

However, previously infected unvaccinated people were in the immediate vicinity. By the fall, the more contagious delta mutants were inherited, but when boosters were not yet widespread, the group had a higher case rate than previously uninfected vaccinated people. It was low.

The Centers for Disease Control and Prevention, which published the study on Wednesday, pointed out some warnings to the study. Also, some outside experts were paying attention to the findings and being wary of how they would be interpreted.

“The key message is that symptomatic COVID infections give rise to some immunity,” said E. John Wheely, an immunologist at the University of Pennsylvania. “But it is much safer to get immunity from vaccination than to get infected.”

Vaccination has long been sought after previous cases of COVID-19, as both types of defenses eventually diminished. And Ali Ellebedy, an immunologist at the University of Washington, added that there are too many unknowns to rely solely on past infections, especially old ones. In St. Louis.

“There are so many variables out of control that it can’t be used as a way to say,’Oh, I’m infected and protected,'” Ellebedy said.

This study with a small cluster of studies found that previously infected unvaccinated people had a lower risk of COVID-19 diagnosis or illness than previously uninfected vaccinated people. It matches.

The results of the new study make sense, said Christine Petersen, an epidemiologist at the University of Iowa. She said vaccines developed against early forms of coronavirus are likely to be less effective against new variants.

However, experts say that the effectiveness of the vaccine has simply declined over time in many people, how much it was involved in what happened to wearing masks and other behaviors, and so on. There are also some possible factors.

Another thing to consider: “not well vaccinated” is unlikely to be tested, and the study includes only laboratory-confirmed cases, Wheely said.

“In the unvaccinated group, reinfection may not be very high,” he said.

CDC officials have pointed out other restrictions. This study, performed before the Omicron mutant was taken over and before many Americans received booster immunization, has been shown to dramatically increase defense by increasing the level of antibodies that fight the virus. increase. The analysis also did not include information about the severity of past infections. Nor was it able to address the risk of serious illness or death from COVID-19.

The authors of the study concluded that vaccination “continues to be the safest strategy” to prevent infection and that “all eligible individuals need to be up-to-date with COVID-19 vaccination.”

Researchers have investigated infectious diseases in California and New York, which make up about 18% of the US population. They also looked at COVID-19 hospitalization in California.

Overall, about 70% of adults in each state were vaccinated. Another 5% have been vaccinated and were previously infected. A little less than 20% were not vaccinated. About 5% were unvaccinated but had been infected in the past.

Researchers examined cases of COVID-19 from the end of May to mid-November last year and calculated the frequency of new infections in each group. Over time, vaccine-only protection has become less and less impressive.

By early October, the case rates were as follows compared to previously unvaccinated people who had not been infected.

— Those who have been vaccinated but have not been infected before are 6 times lower in California and 4.5 times lower in New York.

— Those who are infected but never vaccinated are one-29th in California and one-fifteenth in New York.

— Those infected and vaccinated are 32.5 times lower in California and 20 times lower in New York.

However, the researchers found that the difference in rates between these last two groups was not statistically significant.

Hospitalization data from California alone followed a similar pattern.

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Contributed by AP Medical Writer Lauran Neergaard.

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The Associated Press’s Department of Health Sciences is supported by the Science Education Department of the Howard Hughes Medical Institute. AP is solely responsible for all content.