Omicron may be able to break prior infection immunity: South African study

The Omicron
coronavirus variant could be three times more likely to cause reinfection compared
to the Delta and Beta strains, scientists in South Africa have found raising
further fears over the highly-mutative variant that has now become the dominant
strain in the country and spread to at least 30 others. The paper that makes
the claim has been uploaded on a medical pre-print server but is yet to be
peer-reviewed, reports AFP.

The study is based
on data collected through South Africa’s health system which has seen a steep
spike in COVID-19 cases over the last week as well as a rise in
hospitalisations. The critical aspect of the study is that it provides the
first epidemiological evidence about Omicron’s ability to evade immunity from
prior infection.

Also Read | Delta vs Omicron: Two COVID variants of concern

Until November 27,
there were 35,670 suspected reinfections among 2.8 million individuals with
positive tests. Cases were deemed as reinfections only if patients tested
positive 90 days apart.

“Recent
reinfections have occurred in individuals whose primary infections occurred across
all three waves, with the most having their primary infection in the Delta
wave,” Juliet Pulliam, director of the South African DSI-NRF Centre of
Excellence in Epidemiological Modelling and Analysis wrote on Twitter.

Also Read | Does omicron pose greater risk to infants? Scientists explain

The scientist did
caution that the authors did not have information about the vaccination status
of individuals who had been reinfected and therefore could not assess if
Omicron evades vaccine-inducted immunity. The researchers intended to study
this aspect of reinfection this week.

Pulliam said that
there is urgent need for data on disease severity associated with Omicron
infection, including in individuals with a history of prior infection.

Also Read | Will omicron elude vaccine protection? Some, but not all: Report

Michael Head, a
scientist at the University of Southamptom, called the research high quality
adding that the analysis does look very concerning with immunity from previous
infections being relatively easily bypassed.

South Africa was
reporting just around 200 to 300 cases mid-November. On Thursday, South Africa
reported 11,500 new infections, up from 8,500 Wednesday, from 4,373 the day
before and 2,273 on Monday.