By Mike Stobbe
Associated Press
A study published this Wednesday by the Centers for Disease Control and Prevention (CDC) concluded, based on data collected in California and New York, that a previous contagion of coronavirus protected better from new infections than the vaccine during the waves of the delta variant in summer and autumn.
These findings, published in the CDC's weekly report, seem to contradict the public message from health authorities that defends vaccination as the best way to avoid coronavirus.
But experts consulted insist that immunization is the best way to protect against the most serious symptoms of COVID-19, as well as hospitalization and death.
The researchers examined infections that occurred in both states last summer and fall, and found that people who were vaccinated and had survived a previous COVID-19 outbreak
had the greatest protection
.
Unvaccinated people with a previous infection ranked second in protection.
In the fall, when the delta variant had taken over but booster doses had not yet been distributed, those people had lower diagnoses than vaccinated people who had no previous infection.
The study was done before omicron was imposed as a variant. Ted S. Warren / AP
The CDC pointed to several potential problems with the research, and some
outside experts were wary of the conclusions
and wary of how they might be interpreted.
"The bottom line is that some immunity is generated from symptomatic COVID infection," said immunologist E. John Wherry of the University of Pennsylvania.
"But it's still much safer to get immunity from vaccination than from infection."
Immunologist Ali Ellebedy of Washington University in St. Louis added that vaccination has long been encouraged, even after a previous case of COVID-19, because both types of protection eventually wear off and
there are too many unknowns .
to rely only on a
past infection, especially from a long time ago.
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"There are so many variables that you can't control that you can't use [this] as a way of saying,
'Oh, I'm infected
, so I'm protected,'" Ellebedy said.
The research aligns with a small group of studies that found unvaccinated people with a prior infection had a lower risk of COVID diagnosis or illness than vaccinated people who had never been infected.
The results seem plausible, according to Christine Petersen, an epidemiologist at the University of Iowa. Petersen said a vaccine developed against an earlier form of the coronavirus is likely to be less and less effective against
new, mutated versions.
[You can now order free COVID-19 tests on this Government website: they will arrive in the mail within 7-12 days]
However, according to Petersen and other experts, there are other possible factors at play, such as whether the vaccine's effectiveness simply faded over time in many people, and the extent to which mask wearing and other behaviors played a key role.
CDC officials noted that
the study was done before the omicron variant took hold,
and before many Americans received booster doses, so it's unclear what impact boosters might have.
[The cost of masks and tests for COVID-19 exacerbates the gap of the pandemic among those most in need]
The analysis also did not address the risk of severe illness or death from COVID-19.
