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The latest Omicron coronavirus variant poses a threefold higher risk of reinfection than the dominant Delta variant and the Beta strain, a group of South African health bodies said on Thursday.
The South African Centre for Epidemiological Modelling and Analysis (Sacema) and the National Institute of Communicable Diseases (NICD) said the latest findings “provide epidemiological evidence for Omicron’s ability to evade immunity from prior infection”.
Their statement was issued after a group of South African health organisations published a paper on medrxiv.orgas a pre-print, meaning the work was not yet certified by peer review.
Earlier in the day, microbiologist Anne von Gottberg at NICD had echoed the same views at an online news conference hosted by the World Health Organisation. She said South Africa was seeing an increase in reinfections due to Omicron.
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South Africa had been experiencing a sudden spike in daily infections, with the government reporting 11,535 additional cases on Thursday – up from 312 just 10 days ago.
The NICD said on Wednesday the Omicron variant was able to get around some immunity and was fast becoming the dominant strain in the country. The NICD, alongside a wider network of health organisations, conducts genome sequencing on samples.
Reinfection risk profile
An analysis of routine surveillance data from South Africa from March 2020 until November 27th showed the “reinfection risk profile of Omicron is substantially higher than that associated with the Beta and Delta variants during the second and third waves”, according to the NICD.
An increase of reinfections rather than new infections would be an indication the latest variant has developed the ability to evade natural immunity from previous infection, it said.
Juliet Pulliam, director of Sacema and author of the pre-print paper, said in her article that Omicron's pattern is likely to be established across all provinces of South Africa by early to mid-December, noted the NICD.
The analysis is based on 2,796,982 individuals with positive test results at least 90 days prior to November 27th, out of which 35,670 were suspected reinfections, it added.
South Africa has accelerated its vaccination campaign by giving jabs at pop-up sites in shopping centres and transport hubs to combat the rapid rise in new cases, a week after the discovery of the Omicron variant.
Scientists said they were braced for the surge to continue.
Gauteng province, where South Africa's largest city, Johannesburg, and the capital, Pretoria, are located, is a hot spot of new infections, accounting for more than 70 per cent of the new cases.
Gauteng officials said they were “preparing for the worst” by increasing hospital beds and reopening some field hospitals in anticipation of increased admissions of Covid-19 patients.
Tests indicate that the Omicron variant, first reported in southern Africa, is spreading quickly and is now in five of South Africa’s nine provinces. It is not known how many of the new daily cases involve Omicron because scientists can only do full genetic sequencing on a small number of positive tests.
But it appears that Omicron is “rapidly becoming the dominant variant” in South Africa, according to a statement issued by the NICD. The institute said that 74 per cent of the 249 samples sequenced in November were identified as Omicron.
Is it more contagious?
In October, before Omicron was discovered, the Delta variant was the dominant form of coronavirus in South Africa.
Scientists in South Africa and worldwide are doing genetic sequencing of Omicron samples to learn more about the variant.
Much remains unknown about the strain, including whether it is more contagious, as some health authorities suspect, if it makes people more seriously ill or whether existing vaccines are effective against it.
In a separate development, scientists believe they may have found the "trigger" behind the rare blood clot complications stemming from the AstraZeneca vaccine.
According to an international team of researchers from Cardiff and the US, the reaction can be traced to the way the adenovirus used in the vaccine to shuttle the coronavirus' genetic material into cells binds with a specific protein in the blood, known as platelet factor 4 (PF4).
Researchers think this may spark a chain reaction in the immune system which can culminate in the development of blood clots – a condition known as vaccine-induced immune thrombotic thrombocytopenia (VITT). – Reuters/PA