Prof Salim Abdool Karim Weekly COVID-19 UPDATES

6 March 2023

Regarding the global situation (Figure 1), there were 141,155 reported Covid-19 cases and 927 deaths across the world yesterday. The overall 7-day average number of cases has not changed meaningfully from the week before but deaths have continued to decline in the last week, reaching lows last seen in early 2020, under-reporting notwithstanding.

In South Africa, the trends in reported cases show an increase (Figure 2). But the number of reported cases remains low overall, despite XBB.1.5 assuming unchallenged dominance, accounting for almost all viruses sequenced in South Africa last week. While there has been a consistent increase in cases for the last few weeks (see the inset graph). There has been no concomitant upward trend in deaths – a common pattern now. And this is to be expected since we saw in last week’s email that those with omicron BA.1 or BA.2 immunity have good cross-reactivity to the omicron XBB sub-lineage. 

The trend in South Africa where week on week increases in cases are not accompanied by increases in deaths is not an isolated phenomenon. While it is widely recognised that Covid-19 deaths are now substantially lower, it has not been clear whether this occurred consistently across the globe when cases were increasing. Marothi’s new analysis by continent below (Figure 3) shows that this trend holds true for the African continent. While the continent is experiencing an increase in cases, deaths have remained low. Similar trends are observed in other continents as well, but not consistently so – Europe is starting to see an upward trend in deaths a few weeks after an upward trend in cases. The data from Asia are not interpretable because of China not reporting its cases or deaths. China’s lack of transparency on its Covid-19 epidemiological situation skews global trends as well.

In last week’s missive, I covered the issue of the role in past infection in protecting against re-infection. In short, infection with alpha, beta, gamma and delta did well in protecting against re-infection with pre-omicron variants. However, they did not provide good protection against omicron. 

So, just how common is past infection with pre-omicron and omicron variants? The US CDC released some fascinating data that help address this question in the USA (Figure 4). Overall in people >18 years in the USA, 50% had past infection in the early stages of the omicron wave and another 43% had vaccine immunity only. 30% had both vaccine and natural immunity, ie. hybrid immunity. Towards the end of the omicron wave, past infection rose to 59%. Since there were substantial numbers of people who got omicron infection, it suggests that a lot of people who had infection with past variants also got infected with omicron, ie. those at high risk get infected repeatedly. Those with vaccine only immunity dropped from 43% to 35%, showing that vaccinated people were also getting omicron infection, in line with waning immunity and vaccine escape, but only to a limited extent. Note that the 2 periods being compared are not strictly before and after omicron.

The trends across age are particularly interesting.  In those above 75 years, only 25% had natural infection in the early part of the omicron wave and this rose to 29% in the late part of the omicron wave, indicating that the measures taken by the elderly are doing well in protecting them from natural infection. In those above 50 years in the USA, vaccine immunity is more common than natural immunity. 

I was surprised at these data because other sero-surveys have suggested a higher proportion of natural infection. There are some caveats in interpreting these data – it comes from blood bank testing and may not be representative of the population. Also, serology can be problematic to interpret due to waning immunity. Notwithstanding these challenges, the trends across age in these data show that younger people have a lot more natural infection and hybrid immunity. I will leave it to you to pour over this graph at leisure and find other interesting interpretations. If you see a trend that I did not mention, feel free to let me know by email – I will include it in next week’s email. 

These observations from the CDC sero-prevalence data made me think back to the Great Barringdon declaration (and anti-vaxx) proponents. I was wondering what became of them. An investigation into the Brownstone Institute, which housed several of the GBD proponents reveals that it has grown substantially through links with several far-right organisations (Figure 5). Those against Covid-19 measures and pro-GBD seem to be and seem to attract largely right-wing (and in some cases racist as well) people and groups. They have rallied around the Brownstone Institute. 

Following last week’s email, I received an email from Michael Osterholm explaining that the effectiveness of masks in preventing SARS-CoV-2 is complicated by the role of the very small droplets. He was kind enough to share his group’s writings, which differ with “Your Local Epidemiologist” on this, “Our group has written a significant amount about this issue from the very earliest days of the pandemic. Last week we posted the following commentary on the CIDRAP site that does address the Cochran review and more 

Also, Zulfi Bhutta wrote to me about the Wall Street Journal article referring to a US Department of Energy report concluding that the virus emanated from a lab leak though it conceded that it had a low level of confidence in this conclusion. I have had to deal with nonsensical arguments on the origins during AIDS and now during Covid-19. Amongst the most double-speak arguments I have heard is one where conspiracy theorists cobble together various bits of information to make a conspiracy and suggestions of cover-up but provide no evidence that the virus was actually in the lab or lab staff before the outbreak (which is not available due to China’s lack of transparency on this issue). These same individuals when challenged with natural spillover arguments ask for evidence that the virus was in the Wuhan seafood market animals before the outbreak. In other words, lab leak conspiracy supporters set a bar for proof of a natural spillover that they cannot meet for the lab leak theory!

I was not going to write anything about the Dept of Energy report, but then a few others also wrote to me about it. So, I was going to write something but came across these 2 articles on the issue that were well researched and captured the views of experts in this field. Here is the link to the NPR story, which can be listened to or read. I have also included the Axios article, which is a simple explanation of the evidence needed and why it is unlikely that this evidence will be found.

Have a great week.


Salim S. Abdool Karim, FRS
Director: CAPRISA
CAPRISA Professor of Global Health: Columbia University