Leading South African experts have predicted that Covid-19-related hospitalisations and deaths during the fourth wave will be much lower than the third wave, which could be due to the vaccination coverage.
At a media briefing hosted by the National Institute For Communicable Diseases on Wednesday, researchers said that even in the worst-case scenario, with an increase in gatherings and a hypothetical new variant, hospitals would be able to manage the surge.
Senior lecturer in the Department of Statistical Sciences at UCT Professor Sheetal Silal said they prepared four potential scenarios based on two factors: behavioural change and an introduction of an immune escape variant.
“We can see across all of the scenarios that we don't get anywhere close to the third wave excess deaths levels, even in the highest scenario where we projected an immune escape variant and an increase in contacts,” she said.
Silal said that while hospitalisations and deaths are predicted to be lower than both the second and third waves, the number of Covid-19 cases recorded could be similar.
“We focused on hospital admissions only, rather than on cases as these become less relevant with higher vaccination coverage. Due to the protection offered from vaccination there’s going to most likely be a week and link between cases and hospitalisation.”
The models assume that the vaccines available in the country are less than 100% protective against infection and severe disease. This is based on clinical trial data for Pfizer and Johnson & Johnson against the Delta variant.
It is estimated in the models that approximately 70% of the adult population would be vaccinated by the end of March 2020 with a 75% coverage in over-60s.
“Seroprevalence has allowed us to estimate that between 60–70% of South Africans have had a Covid-19 infection since the beginning of the epidemic, which is much higher than the northern hemisphere,” said Silal.
Here are the four possible scenarios from the South African Covid-19 Modelling Consortium:
Scenario 1
Scenarios 1 and 2 examine the impact of behaviour change in the absence of a new variant together with a growing nonpharmaceutical interventions (NPI) fatigue.
Researchers modelled an increase in person-to-person contact and a growing NPI fatigue where people are less concerned about physical distancing during the festive season. In this model, there was no immune escape variant factored into the projections.
The model projected that the fourth wave and number of hospital admissions could be considerably smaller if behaviour changes start in January instead of November.
Scenario 2
This hypothetical extreme scenario shows a population that does not change their behaviour in response to growing mortality rates due to a wave. It is a complete abandonment of protective behaviour and no new variant of concern.
“The hospital admissions we are projecting under this scenario are still generally lower than what we observed in the second wave in each of the provinces,” she said.
Scenario 3
Scenarios 3 and 4 explore the impact of behaviour fatigue and NPI fatigue but with the introduction of a hypothetical new variant with a 25% relative reduction in protection from both prior infection and vaccination.
This scenario assumes that there is no behaviour change or NPI fatigue in the upcoming months.
“We see a slow increase in admissions across the provinces but slightly higher peaks,” said Silal.
Scenario 4
The final scenario assumes that there will be behavioural changes over the festive season, NPI fatigue will increase and that there will be an immune escape variant in the country.
“We know that the December holidays will have an increase of migration across the country, increased contact behaviour due to people being on leave, and schools closing.”
This projected scenario is what the fourth wave would look like if there was an immune escape variant emerging in November or January and if there is an increase in gatherings.
