For people who previously had and recovered from COVID-19, the risk of reinfection from the omicron variant is about 5.4x higher than it was from the delta variant, according to a new study from UK researchers.
The report from Imperial College London, which has not yet been peer-reviewed, indicates that past infection may provide as little as 19% protection from reinfection with omicron, which is currently spreading rapidly in Britain, the United States and other countries.
"This study provides further evidence of the very substantial extent to which Omicron can evade prior immunity given by both infection or vaccination. This level of immune evasion means that Omicron poses a major, imminent threat to public health," Imperial College Prof. Neil Ferguson said in a statement.
Omicron breakthrough infections rising
The study adds to a growing body of evidence on omicron's potential to cause breakthrough COVID infections and reinfection.
A major South African study this week, looking primarily at the decreased efficacy of vaccines against the omicron variant, also found it had a higher propensity to cause reinfection.
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As of Dec. 13, the state of New York said it was aware of almost 227,000 breakthrough infections to-date, just under 2% of the total population of vaccinated people ages 12 and up.
Symptoms of omicron
There is still an active debate about whether omicron infections are more mild than previous types of COVID infection.
The South African study indicated omicron did appear to be less severe, but the Imperial College study said there was no evidence yet that omicron is milder.
Some with more recent infections have described them as feeling like a bad cold, though as with every wave of COVID, experiences differ.
One indication may come from Google Trends, where searches for "scratchy throat vs sore throat" are up 350% in the last week in the United States, and other searches that pair omicron with various throat-related symptoms are on the rise.
