Reinfection from Omicron more common than previously thought, says new study

London: The incidence of reinfection from the Omicron variant of Covid-19 is more common than previously thought.

A study held in Iceland has defined reinfection as a positive PCR test for SARS-CoV-2a-60 or more days from a previous positive test. It also showed that two or more doses of vaccine were associated with a slightly higher probability of reinfection compared with one dose or less.

Elias Eythorsson of Landspitali-The National University Hospital of Iceland said that the findings should be interpreted with caution because of the limitations of the study including the inability to adjust for the complex relationships among prior infection, vaccine eligibility, and underlying conditions.

The team analysed 11,536 PCR-positive persons and reinfection was observed among 1,327 persons (11.5%) during the Omicron period. In the group that received one or fewer doses of the vaccine, 11.7% were re-infected. Among those who received two or more doses, 10.9% were re-infected. The rate of reinfection was high, 15.1%, in the age group 18-29. This is higher than the older population.

Experts noted that the longer time from initial infection was associated with a higher probability of reinfection. "The difference was smaller than expected." Eythorsson said: "Our results suggest that reinfection is more common than previously thought. Now the key question is whether infection with the Omicron variant will produce better protection against Omicron reinfection, compared with other variants."

Omicron is considered to have a higher transmission rate. The relative protection of prior infection against reinfection with Omicron is known to be 56% compared with 92% for the Delta variant.