- South Africa is expected to have fewer Covid-19 hospital admissions during the predicted fourth wave.
- The scientists behind the report, however, stressed that the prediction was based on modelling.
- They provided a set of scenarios based on different assumptions and drivers.
Hospital admissions and deaths during South Africa's expected fourth wave of Covid-19 infections are "projected to be considerably smaller than those of previous waves" thanks to the country's vaccination coverage, according to the latest report from South African Covid-19 Modelling Consortium scientists.
Using modelling, the team explained during a media briefing on Wednesday that they considered various fourth wave scenarios and took into account vaccinations and variants.
The scenarios were also based on two factors: people's behaviour in the coming months, and the emergence of a hypothetical new variant of concern (VOC) evading vaccine-induced immunity.
The projections, however, should be interpreted with caution, said Dr Sheetal Silal, a statistical scientist who researches mathematical modelling of infectious diseases.
"There is considerable uncertainty in that nobody knows when this next wave is going to start. Nobody can tell you what the next variant is going to look like or when it's going to emerge, and that is why what we are showing today are not forecasts.
"These are scenario analyses, not forecasts. Forecasts take into account the current situation and they give you an idea of what may happen in the future. It's an idea of a probable future. But scenario analyses are 'what if' questions."
By asking "what if", the scientists are able to analyse what the future might hold if their assumptions materialise, she said.
Past infection and vaccine effectiveness
Some key assumptions were:
- Vaccine coverage may reach 70% of the adult population by the end of March 2022 (75% coverage in the 60+ age group), with the 12–17 years age group excluded.
- Vaccines were not fully effective against infection and severe disease, based on clinical trial data for Pfizer and J&J against the Delta variant.
- Vaccine effectiveness against infection was assumed to wane over six months for individuals who were not previously infected with SARS-CoV-2 (the virus that causes Covid-19).
- Vaccine effectiveness against hospitalisation or severe illness does not wane in their projection window.
By 17 November, just over 24.3 million vaccine doses had been administered across the country. More than 60% of adults aged 60 years and older have received at least one dose.
Most realistic scenario
The most realistic scenario, which involves the introduction of an immune escape variant, would be one involving non-compliance with non-pharmaceutical interventions (NPIs), including physical distancing, mask-wearing, and hand sanitising, in the coming months, said Silal. This concept of NPI fatigue is relevant to the upcoming holiday season, migration, and increased contact behaviour as people are on leave, she explained.
But even if this hypothetical variant emerged in November or January 2022, and there was an increase in socialising between people (and therefore Covid-19 transmission), the situation might not be too bleak.
"If we compare the peak of these [hospital] admissions to those observed in previous waves, we can see that in most cases, with the exception of the Free State and Northern Cape, these peaks are generally lower than what was observed in the second and third waves," she said.
According to the report, if increased socialising occurs in January, as opposed to November, "later and smaller waves are expected as a larger proportion of the population will be vaccinated".
Silal said: "Even with continuing NPI fatigue, rapid vaccination of the population provides a powerful tool to reduce severe illness and death."
A message for hospital managers
Despite the above, Silal clarified that it didn't necessarily mean that hospitals would cope during the next surge.
"Some of the emergency measures are no longer in place. Perhaps wards are being reallocated to previous functions; emergency staff are no longer being employed; and elective surgeries are now being allowed.
"What this means is the available capacity to manage an increase in Covid admissions is different to what it was in the second and third waves. That means that even a lower peak than what we had observed in previous waves might be sufficient to breach capacity," she said.
The team's message to planners and those in hospital management was to assess the projections and peak sizes with regard to current hospital bed capacity, and not the capacity that was available during previous waves.
The report read: "Whether or not the admissions will result in overwhelmed hospitals and avoidable Covid-19 deaths also depends on how much hospital capacity can continue to be made available."
Virus to become endemic
What’s clear now is that the current vaccines' effectiveness against infection is not high enough to eradicate SARS-CoV-2, said Dr Harry Moultrie, a senior epidemiologist at the National Institute for Communicable Diseases (NICD).
"This means that we are on a long road trajectory towards endemicity. What we're going to see is waning of immunity (either natural immunity or vaccine-derived immunity); we're going to see new people entering populations because of births ... and so we're going to see fluctuations of SARS-CoV-2 for many years to come."
Not set in stone
At the moment, it's unclear to what extent the virus will be influenced in the long run.
"It's going to be a bumpy ride," said Moultrie, and there could be substantial resurgences in the years to come. He added that there was still a lot of space for viral evolution.
'We don't know where this virus is going to take us. It has surprised us a number of times to date in the last 18 months. But in the long run, we are going to move towards endemicity where people get re-infected (with mild infections) and get re-boosted with vaccines or infections."
Resurgences will be manageable, he said, but South Africa will still see Covid-19 admissions and deaths for years to come.
"But the future of the epidemic is not set in stone," said Moultrie. Instead, it is determined by every person's behaviour as well as the virus's evolution and how those two interact. He stressed the importance of continuing to follow public health measures, such as avoiding crowded indoor spaces, wearing masks, and hand sanitising going forward, as people approach the holiday season into December