Omicron in South Africa: even milder than expected - UnHerd



Every number has come in under the projection

by Pieter Streicher

Two weeks ago, when panic about the Omicron variant of Covid was at its peak and it felt imminent that the UK would be going back into lockdown, I gave an interview to UnHerd's Freddie Sayers. I am a PhD in engineering and a research associate at the IFK University of Johannesburg — I am not an epidemiologist — but I had been closely following the data of the Omicron wave that started in Gauteng province in my home country of South Africa.

On 4th of December I put together some basic projections for all the main Omicron variables — cases, hospital beds, ICU beds, ventilated beds, deaths — using simple growth rate extrapolations. Each variable goes through an exponential phase during which daily growth peaks, followed by a period with a consistent decline in growth rate. This consistent decline makes it possible to predict the date of the peak with reasonable accuracy. Once a likely date range for a variable has been determined, it becomes easier to gauge the likely peak levels of all variables. It was clear already by then that the Omicron wave was going to be extremely mild compared to the Delta wave, which my forecasts confirmed.

All the figures have come in under the projected values

What has been remarkable in the intervening weeks — despite the very clear data trends and statements of practitioners like Dr Angelique Coetzee, head of the South African Medical Association, that the variant was mild in all groups — is how slow other countries have been to accept this as fact. Sir Patrick Vallance and Chris Whitty, the UK's chief scientific and medical officers, seem to be the last to admit what has been evident to most observers for almost a month: namely, that Omicron is much milder than Delta. With numbers in UK hospitals rising, a degree of caution is of course understandable, but the refusal to acknowledge the evidence from South Africa has been odd.

It is true that South Africa is a very different country to the UK, with a younger population and a different profile of prior immunity. But the population also has a major obesity problem, poor metabolic health, widespread HIV and had been hit relatively badly by previous waves of the virus. So the idea that 'just because Omicron has not done much damage in South Africa it could still be devastating in the UK' was always hard to believe.

In fact, the Omicron wave in Gauteng turned out to be even milder than my forecasts suggested; since the interview, every single one of the variables came in below projected levels. My estimate that deaths would be 25 times lower than the Delta wave still holds, and I have revised my estimate for the infection fatality rate down from 0.053% (11th December) to 0.036%.

As all variables seem to have peaked, we can also make estimates of the peak numbers per 100,000 — which should be useful for planning purposes in other regions and nations.

0/Post a Comment/Comments