COVID-19 infection may offer similar immunity as vaccination
COVID-19 infection may offer similar immunity as vaccination

COVID-19 infection may offer similar immunity as vaccination

In the pre-Omicron variant era, previously symptomatic COVID-19 infection in unvaccinated patients provided a level of protection against subsequent infections at the level of mRNA vaccines, but prolonged, according to a US examination of more than 121,000 participants published today in JAMA Network Open.

Of course, the results do not suggest that infection is preferred over vaccination, which is the much safer alternative.

Nearly 120,000 patients examined

Researchers from the University of Chicago led the study using data from COVID-19 test results at 1,300 locations in six western states at Providence Health & Services from October 1, 2020 to November 21, 2021. Both vaccinated and unvaccinated patients were monitored for COVID- 19 infection starting 90 days after vaccination or initial illness.

A total of 24,043 unvaccinated, previously infected patients and 95,572 vaccinated patients (controls) tested positive during the study period. Among them, 0.4% of previously infected patients and 2.8% of the controls tested positive for COVID-19 during the study period.

Previously, COVID-19 was bound to protection of 85% against re-infection, 88% against hospitalization and 83% against COVID-19 that does not require hospitalization. This protection remained stable without decreasing up to 9 months after the first disease.

Hazard ratio (HR) to test positive for COVID-19 among previously infected patients was 0.15 (95% confidence interval) [CI]0.13 to 0.18), while it was 0.12 (95% CI, 0.08 to 0.18) for COVID-19 admission and 0.17 (95% CI, 0.13 to 0.21 ) for infection that does not require hospitalization.

Vaccination ‘significantly safer’ than infection

The study authors said their results are similar to those of previous studies that found COVID-19 protection given by previous infection at 80.5% to 100%. “The results of this study may have important implications for vaccine policy and public health,” they wrote.

The results, the researchers said, “suggest that natural immunity was associated with similar protection against mild and severe disease,” they added. “mRNA vaccines are associated with similar long-term protection against severe COVID-19 as found in our study, although vaccine-associated protection against mild COVID-19 has been shown to decrease after 6 months.”

In a Providence Press releasesaid senior author Ari Robicsek, MD, that while previous infection provided similar protection as mRNA COVID-19 vaccination, “vaccination is a significantly safer way to gain that immunity.”

The study’s limitations include the possibility that participants may have undergone COVID-19 testing or vaccination at a health facility outside the Providence system, and COVID-19 survivors may behave differently than coronavirus-na├»ve participants, the researchers warned. “Strengths include large sample size, long duration of follow-up, and inclusion of only unvaccinated individuals with symptomatic COVID-19,” they wrote.

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