Researchers from the University of Washington say it's the most comprehensive data compiled so far showing national immunity protection against the virus. The findings were released Thursday, Feb. 16 in the peer-reviewed journal, The Lancet.
The research identified and analyzed 65 studies from 19 different countries.
"Our meta-analyses showed that protection from past infection and any symptomatic disease was high for (COVID-19) ancestral, alpha, beta, and delta variants, but was substantially lower for the Omicron BA.1 variant," the report said.
Protection from re-infection from ancestral, alpha, and delta variants declined over time but remained at 78.6 percent at 40 weeks (around 10 months). Protection against re-infection by the Omicron BA.1 variant declined more rapidly and was estimated at 36 percent over that same 40-week period, the report states.
On the other hand, it said, protection against severe disease remained high for all variants, with 90.2 percent for ancestral, alpha, and delta variants, and 88.9 percent for Omicron BA.1 at 40 weeks.
The US Centers for Disease Control and Prevention (CDC) says there are still an average of over 40,000 new COVID cases in the country per day.
Since protection from COVID does not last forever (unlike some other viral infections such as chickenpox or measles) even those with natural immunity will probably still need an annual COVID booster shot, according to the CDC.
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