Covid models are not always 100% correct, say experts

SOUTH African Medical Association (SAMA) chairperson Dr Angelique Coetzee says the Covid-19 third wave is not likely to come this month as earlier projected.

“Most probably next month or maybe July … it depends on behaviour mostly. Even the latest modelling has hesitated to give a time frame – it all comes down to how well individuals and groups adhere to social distancing rules,” said Coetzee, adding that the latest modelling does not give a time frame due to inaccurate data available despite a notably steady increase in the number of new infections across the country.

The South African Covid-19 Modelling Consortium had earlier warned of a potential third wave this month, adding that in the absence of a new variant, the peak would be lower than the first and second waves.

Coetzee said models do their best to approximate reality, however, modelling is always based on assumptions of what may happen in reality, based on data available to the modellers at the time, and the assumptions are usually based on variables that can change quite considerably.

“There is no 100% guarantee as it is a prediction. All over the world, modellers are struggling to get it 100% correct.”

Meanwhile, award-winning independent public health practitioner Dr Shakira Choonara concurred that models have had their shortfalls.

“In the early days of the pandemic, there were worst-case scenarios, presentations of the peak, number of deaths, etc. by the then chairperson of the Ministerial Advisory Committee (MAC) Professor Abdool Karrim.

“In terms of the best and worse case scenarios presented early in the pandemic, South Africa has averted the worst case scenario; we have a high recovery rate and a low number of deaths,” said Choonara, adding that agencies should always refer to the National Institute of Communicable Diseases (NICD) for official and regular information.

She said there needs to be synergy between modelling and finding ways to come together to disseminate information for the public.

“Looking to other countries as well as our own experience, the third wave and any subsequent waves are likely in the absence of large-scale vaccine rollout and there could be unexpected factors such as the spread of new variants,” said Choonara.