Ross Clark Ross Clark

What does this South African study reveal about Omicron?

A healthcare worker in Pretoria prepares to administer a Covid vaccine (Getty images)

While the government’s policy on Omicron is being driven by modelling suggesting the possibility of a huge wave of hospitalisations in January, some more real-world data has come in from South Africa. 

A presentation by the South African Medical Research Council this morning has offered evidence that while Omicron does indeed appear to be more transmissible than the Delta variant, the trajectory of hospitalisations is flatter. 

This would appear to confirm earlier data from hospitals in Gauteng province that Omicron is causing a milder disease than previous variants. Indeed, the graph of the latest outbreak shows a marked decoupling on infection figures for hospitalisation and death figures, compared with earlier waves:

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The data indicates that Omicron is 29 per cent less severe than the original Wuhan strain of Covid. However, it also seems to confirm that Omicron is better able to escape the Pfizer vaccine compared with the Delta variant. Efficacy against infection fell from 80 per cent to 33 per cent, while efficacy against severe disease fell from 93 per cent to 70 per cent. That is data for vaccine efficacy – it has to be weighed against evidence that Omicron is less likely to cause severe disease.

What effect will the new South African data have on UK policy? For now, the current approach appears to have been driven by modelling from the London School of Hygiene and Tropical Medicine (LSHTM) paper of 11 December on the Omicron variant. But this document is fast achieving the notoriety of Imperial College’s paper of 16 March 2020: the one which persuaded the government to change course from a herd immunity strategy to one of suppression, and which led to the first lockdown. 

The LSHTM paper, published on Saturday, set up four scenarios regarding the spread of Omicron, the most pessimistic of which sees hospitalisations for Covid rise to a peak of 7190 a day in January – 60 per cent higher than the peak of January 2021.

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