Had Covid-19 already? SA warned natural immunity unlikely to protect against reinfection with Omicron

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  • A high percentage of people in SA have been infected with Covid since the start of the epidemic.
  • But this previous infection is unlikely to protect against reinfection with the Omicron variant.
  • Covid cases are rising fast in the country, with hospital admissions on the increase.

Early evidence from researchers in South Africa suggests that Omicron, the new Covid-19 variant of concern, has a “substantial” ability to escape protection from past natural infection.

The scientists, at the National Institute for Communicable Diseases (NICD), published their findings to preprint server medRxiv on Thursday, AFP reported.

This is the first real-world study looking at the Omicron variant’s ability to evade immunity derived from natural infection – and it was found that the risk of reinfection was lower with the Beta and Delta variants, which dominated SA’s second and third waves. 

The team warned that their findings have important public health implications, “particularly in countries like South Africa with high rates of immunity from prior infection”.

Risk of reinfection 2.4 times higher

This risk of reinfection with Omicron was found to be 2.4 times higher when compared to Beta and Delta, the researchers noted.

Michael Head, a scientist at the University of Southampton, said that the analysis looked “very concerning”, AFP reported.

“Might this all still be a 'false alarm'? That is looking less and less likely,” he said.

The SA Covid-19 Modelling Consortium team recently stated that around 60–70% of people in the country had been infected with the virus throughout the past three waves of infections.

The current study did not assess Omicron’s impact on vaccine-induced immunity, or whether the reinfected cases with the new variant were more likely to have severe disease, but Dr Juliet Pulliam, one of the study's co-authors, said the team plans to study this next. 

"Data are also urgently needed on disease severity associated with Omicron infection, including in individuals with a history of prior infection," she tweeted.

In a media briefing on Friday, Dr Michelle Groome, head of the division of public health surveillance and response at the NICD, said that it was too early to say whether Omicron causes more severe disease than previous variants.

Hospital admissions on the rise

Hospital admissions have been increasing nationally, but admission trends in Gauteng were higher than in the previous waves, said Dr Wassila Jassat, Public Health Specialist at the NICD. It is believed that the rapid rise in cases in the province are being driven by Omicron.

Health minister Joe Phaahla said that there had been a steep rise in Covid cases in the last seven days. "It is much steeper than all the other curves we have seen in the last three waves," he said.

Cluster outbreaks started in Tshwane, but it has since spread across Gauteng and other provinces. 

However, he stressed that the vaccines are likely to remain protective, even in the face of Omicron. 

"The evidence is very clear thus far, like all previous variants protection lies with vaccination. We must not hesitate to take the vaccine. It offers protection from serious illness and hospitalisation,” he said.

Additional reporting by Tebogo Monama

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

READ | Covid-19: Reinfections three times more likely with Omicron variant, early research finds

READ | Omicron variant: Why everyone still needs to be vaccinated, even if they've had Covid-19

READ | More reports that Omicron appears to cause mild Covid - but too early to say for sure, experts warn

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