OPINION | What should SA’s virus endgame strategy look like?

SA has aggressively intervened to contain the local coronavirus  epidemic. But it is far from clear which strategic outcome is being pursued. Is it following the lead of countries such as New Zealand or South Korea and trying to stop virus transmission altogether until a suitable vaccine becomes available? Or is it attempting to manage the infection rates so that extreme peaks in morbidity are prevented?

As the government’s strategy is not currently explicit, the intervention framework implemented so far appears consistent with a wide range of possible policy objectives. The rapid emergence of the pandemic defaulted policy to intervene first and ask questions later. But the dust is now settling, and the strategic endgame can and should be made transparent.

Any strategy requires a rational combination of what is known with what isn’t. What’s not known includes the possible outcomes of interventions, as well as contingencies that can materially influence the trajectory of the disease. Given the substantial uncertainties of disease elimination, SA should adopt at least a multi-year strategic perspective — that is the time until a vaccine or treatment is probable and has been implemented.

The strategy should, however, allow for the possibility that each month introduces more certainty about the success of public health interventions and the options for treatment and vaccines.

We discuss three possible approaches, and consider the efficacy of each.

The various options mapped out below take into account what is known, and what is not.

What’s known: First, the  coronavirus is highly infectious. In the absence of interventions it has an average reproduction rate (R or R0) every four days of roughly 2.5. Infections are also associated with levels of morbidity and mortality that make an active public health response necessary.

Second, no vaccine is available yet and no drug has been shown to prevent transmission. Third, no virus-specific treatments exist to mitigate the current levels of morbidity. Fourth, the complexity of the economic and social problems arising from general lockdowns brings a new range of severe socioeconomic problems.

Where does uncertainty lie? First, the extent to which one can rely on social distancing and lockdown strategies in SA’s high-density, poor and informal settlements is in question.

Second, SA appears unable to get testing to the levels necessary to successfully manage a health prevention strategy based on testing and contact tracing.

Third, it is unclear when a vaccine will become available.

Fourth, therapeutic options based on existing treatments are still speculative and unlikely to prove wholly successful.

Fifth, therapeutic options based on new technologies are unlikely to be available in SA until the latter part of 2021.

Given the above background we explore three options that SA could pursue.

Option 1 is to target complete disease control within 2020, without waiting for a successful treatment or vaccine. This would require that public health interventions achieve a sustained reproduction rate of the disease (R) below 1. This would require selective, targeted lockdowns, ongoing social distancing and high rates of population testing, tracing and quarantining.

Option 2 is to keep new infections relatively low, but accept that the epidemic will continue until a vaccine or some other treatment becomes available. This strategy would require keeping the R at around 1, by limiting daily, countrywide new infections to roughly 250 to 300. This approach is premised on the assumption that no public health approach, or other intervention, will be able to eliminate the epidemic in 2020, but that a combination of treatment and vaccinations will do so during the course of 2021.

Option 3 is to keep new infections sufficiently low that they prevent excessive morbidity at any point in time to avoid health services becoming overwhelmed, but sufficiently high as to achieve early herd immunity within, say, the next 18 months. While this approach assumes an average R of more than 1 for an initial period and roughly 1 thereafter, the daily levels of new infections would be higher than option 2, but should still be kept manageable using targeted public health interventions.

Of the above, the third option — allowing infections to rise to achieve herd immunity — is ill-advised, at least for now. To achieve herd immunity over a period of just two years, assuming that only 60% of the population would need to have achieved immunity, would require roughly 51,000 new infections per day. At these levels it can be expected that more than 2,500 people will require hospitalisation each day and that approximately 500 will require intensive care, most of whom would die.

This leaves options 1 and 2. A generalised lockdown is unlikely to succeed as a preventive option in SA. As a result much depends on whether more focused public health measures — such as testing and contact tracing, social distancing, employer health protocols, generalised requirements to wear masks and border management — are sufficient to hold R at 1 or below 1. If these interventions can’t be relied on, the outlook for SA would be bleak, as a runaway epidemic would be more, rather than less, probable. The de facto consequence would be option 3.

But it is plausible that a strategy able to maintain a low level of daily new infections over a two-year period could hold out the opportunity for disease elimination if public health prevention improves over time.

For instance, while significant constraints exist to scale up testing, contact tracing and quarantining in the short term, these can reasonably be expected to lift progressively over a 12-month period.

The current best option is for the government to pursue option 2 as a minimum strategic goal — keep new infections relatively low, but accept that the epidemic will continue until a vaccine is available.

Alex van den Heever; Imraan Valodia ; Lucy Allais ; Martin Veller ; and  Willem Daniel Francois Venter are academics at the University of the Witwatersrand. This article was originally published in The Conversation.

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