SA COVID Study: ‘No Longer at Code Red’, Prof Madhi Says

Commenting on a recently published South African study showing a high COVID antibody sero-prevalence and decoupling of hospitalisation and death rates, first author Professor Shabir Madhi said that “we [are] no longer at “code red’.”

The study, published in the New England Journal of Medicine, was conducted in Gauteng from October 22 to December 9, 2021, showed a high sero-positivity rate even as the Omicron wave started. Under-12s (56%) had the lowest rate of sero-positivity, while it was 80% in over-50s and 85% in inner city residents. Unsurprising, vaccinated individuals had much higher rates (93%) than unvaccinated ones (68%). Epidemiologic data showed that the incidence of COVID infection increased and subsequently declined more rapidly during the fourth wave than it had during the three previous waves.

The researchers imputed 10.4 million infections, compared to the <1 million COVID cases recorded before Omicron. The researchers also evaluated COVID epidemiologic trends in the province, including cases, hospitalisations, recorded deaths, and excess deaths from the start of the pandemic through January 12, 2022.

At time of Omicron wave onset, 59159 Covid attributable deaths using excess mortality data (rate 396/100,000) in Gauteng. Infection fatality risk for Gauteng 0.57% pre-omicron (substantially higher than 0.019% imputed for seasonal flu pre-Covid calculated using similar methods).

In Gauteng at the start of the Omicron wave. vaccine coverage 36% for at least 1 dose in Gauteng, but 61% in over-50s (responsible for >80% deaths pre-Omicron). The sero-survey showed that, 70% of vaccinated were also infected pre-omicron, indiciating a substantial prevalence of hybrid immunity

Prof Madhi further noted analysis of the incidence trends shows a “massive decoupling” of COVID cases to hospitalisation and death rates over the course of Omicron dominance, which was seen in all age groups.
Omicron was responsible for only 3% of COVID deaths compared to 50% for those in Delta-dominant waves. In the 50-59 age group, Omicron was responsible for only 2% of deaths compared to 53% of Delta-dominant deaths.

They also found that children under 12 were not seriously affected during the Omicron wave, with the Omicron wave making up 26% of hospitalisations and 17% of deaths versus 39% and 47%, respectively with the Delta wave.

The researchers concluded that the SA experience indicates that we are now moving into the convalescent phase of the COVID pandemic. Prof Madhi noted in his tweets that this is likely to be similar in other countries that have had a low or modest vaccine uptake, but which have also seen high rates of natural infection – which, in low- and middle-income countries, has likely been accompanied by significant under-reporting of COVID fatalities. 

Given low rates of vaccine rollout and donations, Africa should focus on vaccinating its vulnerable elderly population, Prof Madhi recommended.

He tweeted that SA had expressed optimism that the pandemic had reached a turning point “which many in high income countries dismissed as ’empirical’ and not applicable to their settings despite high vaccine coverage,” subsequently materialised around the world wherever COVID was “not [a] zero-sum game.”