MODELLING CONSORTIUM (PROJECTIONS)
COVID-19 MODELLING UPDATE: CONSIDERATIONS FOR A POTENTIAL FOURTH WAVE (17 November 2021)
The South African COVID-19 Modelling Consortium was established to project the spread of the disease to support policy and planning in South Africa over the coming months. Due to the rapidly changing nature of the outbreak globally and in South Africa, the projections are updated regularly as new data become available. As such, projections should be interpreted with caution. Changes in testing policy, contact tracing, and hospitalisation criteria will all impact the cases detected as well as the number of hospital admissions and deaths that can be positively identified as associated with COVID-19.
Our updated projections show the following:
- This report focuses on projections of hospital admissions as the primary outcome. The numbers of infections and detected cases may be comparable to earlier waves, depending on the scenario; however, the ratio of admissions and deaths to infections and cases is expected to be substantially lower than in previous waves, as a result of the vaccination coverage, particularly among the elderly, and protection from prior exposure.
- Model scenarios depict admission waves of different sizes in each of the provinces as a result of changes in behaviour, which reflects a combination of government-imposed restrictions and individual actions.
- Even in the hypothetical scenario of a complete abandonment of a behavioural response to resurgence, the size of the 4th wave in admissions is projected to be smaller than the 3rd wave, in the absence of a new variant.
- If a variant with a 25% relative reduction in protection from prior infection and vaccination enters circulation, the resultant wave in admissions is expected to be higher (compared to the no variant scenarios), though vaccines will continue to have an impact and may protect the most vulnerable from severe illness.
- If increases in contacts occur in January, as opposed to November, later and smaller waves are expected as a larger proportion of the population will be vaccinated.
- It is important to note that smaller peaks in admissions do not necessarily imply that future waves will have less impact on the health system and health care workers. 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.
- Even with continued behavioural fatigue, rapid vaccination of the population provides a powerful tool to reduce severe illness and death.