null
Covid-19
Omicron’s capacity for reinfection appears unprecedented
But early data suggest its symptoms are milder
TWO WEEKS AFTER the Omicron variant was identified, hospitals are bracing for a covid-19 tsunami. In South Africa, where it has displaced Delta, cases are rising faster than in earlier waves. Each person with Omicron may infect 3-3.5 others. Delta’s most recent rate in the country was 0.8.
Moreover, Omicron has unprecedented capacity for reinfection. A recent study showed that the number of South Africans who test positive at least 90 days after their last positive test is more than you would expect based on earlier waves. And antibodies generated by Pfizer’s vaccine are less effective against Omicron than against earlier variants.
Data on virulence are more heartening. In hospitals Omicron has not yet shown a pattern of worse disease in older people. Among covid-positive hospital patients in the South African city of Tshwane, 70% of those aged 50-69 and 90% of over-80s had severe cases during the Delta wave. This share is now around 30% for all ages.
Sources: NICD, South Africa; Trevor Bedford; “Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa”, by J.R.C. Pulliam et al. (working paper)