Prof Salim Abdool Karim Weekly COVID-19 UPDATES

13 February 2023

Let’s start with the global situation (Figure 1). Yesterday, there were about 165,650 reported cases and 1,733 deaths across the world. The overall 7-day average number of cases declined by more than 10% in the last week (actual cases are much higher). Deaths have also declined in the last week. The map on the right side of Figure 1 shows the countries that have high case rates. 

In Figure 2 below, I have provided the 5 small countries (population < 20 million) and the 5 large countries (population > 20 million) that are the biggest contributors to new cases over the last 7 days. Note that the colour code on the number indicates the incidence rate ie. those that are yellow are large increases off a low base while red indicates both large numbers of confirmed cases and high incidence rates. Taiwan, Japan and South Korea have both rising numbers of cases and high incidence rates. Figure 3 provides similar data for deaths.

Figure 4 below provides a snapshot of the latest distribution of variants in selected countries from each continent/region. 3 omicron variants – BA.5, BQ.1 and XBB continue to be the most common viruses being transmitted in the past 2 weeks. The fraction due to XBB is increasing.

South Africa remains in low transmission, though small outbreaks are continuing to occur (Figure 5). These localised transmissions are resulting in small increases in cases. While still low, deaths are also increasing in South Africa.

Today, I am providing some updates on the issues I covered in the last few weeks. 

On cholera, you may recall my missive on the sharp rise in cases in Malawi. When I met with Trevor Mundel over lunch this week, he informed me that the Gates Foundation was providing Malawi with cholera vaccines. There are concerns about global cholera vaccine supply, which the Foundation is addressing. 

South Africa had its 3rd case of cholera this week. Importantly, this 3rd case acquired the infection locally and is not an imported case. At this time, there is no need for concern. However, poor sanitation in South Africa’s informal settlements, where rivers are still a source of water for locals, could pose a potential threat to the spread of vibrio cholera in these settings. 

Thanks for the many comments on last week’s Paxlovid update. Several people wrote to me about whether Paxlovid should be prescribed to those below 65 years in light of the data provided in the article by Arbel et al in the NEJM showing no benefit in those below 65.

I realised that in trying to be brief, I did not provide adequate information on the real world effectiveness of Paxlovid across the different age groups. There are now several studies on the impact of Paxlovid in clinical practice; I will summarize just 2 of them, which capture the key benefits across many studies.

In the Lancet ID article in Figure 6, Paxlovid reduced hospitalisations by 55% and deaths by 85% across all ages combined. While the benefits were more marked in the elderly (where those above 65 years had 63% lower hospitalisation), the benefits were also present in those 18 to 64 years, where a 47% reduction in hospitalisation was observed. 

One of the largest analyses is the EPIC study which included 567,560 patients - 146,256 received Paxlovid and 421,304 did not. I have attached the results of this study for those who want more detail. In Figure 7 below, the differences in the hospital admission rates and case fatality rates are self-evident. The benefits of Paxlovid on hospitalisation are present in all age groups, but the scale of the benefits gets progressively lower going from the elderly to the young. The authors use a cutoff of 50 years to make their point that hospitalisation is 3 times lower in people under 50 years who took Paxlovid.

In summary, anyone above the age of 18 years taking Paxlovid would have a lower risk of hospitalisation. The reductions in hospitalisation rates in those below 50 years are modest, while those above 50 years derive substantial clinical benefits from Paxlovid. 

The results of a trial using pegylated interferon lambda to treat Covid-19 was published in the NEJM this week. The results were somewhat surprising. Various interferons have been studied in multiple trials but have had little or no meaningful clinical benefit. Figure 8 below provides a snapshot of some of the key trial results, illustrating the lack of clinical benefit or when some benefits were observed, they mainly related to time to recovery – not hospitalisation or death. 

In contrast to the past disappointing results from interferon trials, pegylated interferon lambda halved hospitalisation of emergency room visits. While this may not look as impressive as the Paxlovid trial outcomes, this is an important finding because interferon may be helpful in future respiratory epidemics. Interferon lambda receptors are more plentiful in the respiratory system, which may explain why it is more effective than other interferons. Its success in reducing Covid-19 severity suggests that there is a good chance that it may be effective as a treatment of future respiratory epidemics

To summarise:
  1. Cholera is continuing to spread within Malawi and now has started spreading in South Africa.
  2. Anyone above 18 years taking Paxlovid derives the benefits of a lower hospitalisation rate, but the benefits diminish with age.
  3. Pegylated interferon lambda showed early promising results in reducing hospitalisation from Covid-19. This could be important for future respiratory viral epidemics.    
Have a great week.
Salim S. Abdool Karim, FRS
Director: CAPRISA
CAPRISA Professor of Global Health: Columbia University