Most omicron cases are reinfections, research in England suggests
Most omicron cases in England are among those who have previously been infected with the coronavirus, research suggests.
Imperial College London's React continual study throughout the pandemic found 64.6 percent of cases from Jan. 5 to Jan. 20 were among those who said they previously had COVID-19.
The researchers caution it is unclear which cases are reinfections and which cases are just recent infections that the PCR COVID-19 test picked up again despite the patient having already recovered from it.
The study said the individuals self-reported if they had a previous COVID-19 infection.
Analyzing the genetic history of some of the cases, the group found 99 percent of the cases in that time frame were from the omicron variant and only 1 percent were made up of the delta variant.
"We observed unprecedented levels of infection with SARS-CoV-2 in England in January 2022 and almost complete replacement of Delta by Omicron," the researchers wrote.
React has been analyzing COVID-19 numbers monthly since May 2020 and found 4.41 percent of the 100,500 swab coronavirus tests were positive in January.
It is the highest recorded positivity since the study began and three times higher than in December.
The high number of cases comes as omicron is known to be more infectious than previous variants, but causes less severe illness than the delta variant.
