Omicron variant is ‘at least 2.4x more likely to re-infect’ than original Covid strain

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A study from South Africa found that the risk of reinfection in November, when the Omicron variant of coronavirus was circulating, was 2.39 times higher than in the first wave of the pandemic

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The Omicron variant of coronavirus is 2.4x more likely to reinfect people than the original stain, a study from South Africa suggests.

The research, which has not been peer-reviewed, found people who had tested positive for Covid could pick up the virus again.

It did not say how the variant will behave when spreading in a highly vaccinated population such as the UK, or whether the virus can evade the protection offered by vaccines against severe disease.

The new study estimated that the risk of reinfection for November 1 to 27, when Omicron was circulating, was 2.39 times higher than in the first wave of the pandemic in early 2020.

In contrast, the risk of reinfection in South Africa was lower in the Beta and Delta waves than in the first wave.

The findings suggest Omicron could cause a wave of infections in people with some prior immunity.

The Omicron variant of coronavirus has “substantial” ability to cause reinfection, a study suggests
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Image:

SIPA USA/PA Images)

The researchers, from the National Institute for Communicable Diseases (NICD), looked at data from almost 2.8 million people with Covid-19 who had a positive test result at least 90 days before November 27.

Some 35,670 suspected reinfections were identified among the 2,796,982 people (1.2%).

The authors concluded: “Population-level evidence suggests that the Omicron variant is associated with substantial ability to evade immunity from prior infection.

“In contrast, there is no population-wide epidemiological evidence of immune escape associated with the Beta or Delta variants.

The findings suggest Omicron could cause a wave of infections in people with some prior immunity
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Image:

POOL/AFP via Getty Images)

“This finding has important implications for public health planning, particularly in countries like South Africa with high rates of immunity from prior infection.

“Urgent questions remain regarding whether Omicron is also able to evade vaccine-induced immunity and the potential implications of reduced immunity to infection on protection against severe disease and death.”

Dr Abdou Salam Gueye, regional emergency director for the World Health Organisation’s Regional Office for Africa, told a press briefing there was concern about reinfections.

She said: “We monitor these reinfections (and) for the Beta and for the Delta wave we didn’t see an increase in reinfections over and above what we (would) expect when the force of infection changes when the wave stops.

“However we are seeing an increase for Omicron. And that speaks to the fact that in our population with a high seroprevalence – so where many people have had previous infection – we believe that their previous infection does not provide them protection from infection due to Omicron.

“However, hopefully it provides them with protection against severe disease, hospital admissions and death.”

She said the susceptibility of the population of South Africa “is greater now because previous infection used to protect against Delta and now with Omicron and doesn’t seem to be the case”.

But she added: “We believe that vaccines will still, however, protect against severe disease because we’ve seen this decrease in protection using vaccines with the other variants – the vaccines have always held out to prevent severe disease and admission into hospital from death.

“The same things that held true for the other variants, I think, to a large extent hold true for this variant.”

Professor Francois Balloux, from University College London (UCL), said the findings were not surprising given the number of mutations in the new variant. He said the research could not account for waning levels of immunity.

He added: “Risk of reinfection by the Omicron variant was estimated to be around three times higher than by the Alpha and Delta variant.

“The study is competently performed and highly timely as it provides the first direct evidence for the increased ability of the Omicron variant to partially bypass prior host immunity conferred by prior infection.

“The study does not provide any insight on the robustness of vaccine-induced immunisation against the Omicron variant. It also does not report any data on infection severity.

“South Africa has a low vaccination rate but a large proportion of the population has been infected during previous Covid-19 waves.

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“The population of South Africa also tend to be fairly young with a median age of 27.6 years.

“As such, the results from this study are not directly portable to other settings such as Europe or North America, and more data will be needed before we can make more any robust prediction about the potential threat posed by a global spread of the Omicron variant in different parts of the world.”

Dr Michael Head, senior research fellow in global health at the University of Southampton, said: “This analysis does look very concerning, with immunity from previous infections being relatively easily bypassed. Might this all still be a false alarm? That is looking less and less likely.

“We do not yet have up-to-date information on vaccine effectiveness.

“However, the situation should, to some extent, be different with vaccine-generated immunity. The immune response from vaccination is much stronger when compared with infection-acquired immunity.

“Whilst there is likely to be some impact, it is likely vaccines will still provide some level of protection.

“The booster dose may be key here in maintaining a high level of protection.

“Whilst we await more data to emerge over the coming days and weeks, the message to the general public has to be: go and get all the doses you are eligible for. Keep that protection as high as possible.”

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George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.

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