Prof Salim Abdool Karim Weekly COVID-19 UPDATES
- A week ago, the 7-day moving average was 3,097 (slide 2) – today it is 52% higher at 4,693 (slide 3). If we were in a wave, the 7-day moving average would have doubled every 2-3 days (and so we would have expected over 10,000 cases per day a week later), given the high transmissibility of omicron and its sub-variants. We have only seen a modest rise in cases. However, the problem could be that the increased case numbers are not evident because the holidays have led to a situation where testing has not increased as expected. That testing is so low that we are only seeing a 52% rise in cases even though cases are going up much more than this.
- The slow increase (perhaps more aptly referred to as a meandering increase) is evident in slide 5 – compare the green and red lines after they each hit the threshold of 5 cases per 100,000 population per day. Looking inside the red circle on slide 5, the slow increase is evident when comparing it to the omicron BA.1 increase we saw in SA in December last year.
- The slowing of the increase in cases (provided it is not an artifact of the holidays) is evident across the board in most provinces. While the increases looked steady and rapid the previous week (slide 22), they are slowing this week and are not following a rocket-like upward trajectory (slide 23), we would expect in a 5th wave.
- A few weeks ago, I shared the Rossler data (slide 6) from the NEJM showing that omicron generated good immunity to the past variants of concern. I pointed out that omicron has spread quite widely due to its high level of infectiousness and so many people (most, in some countries) have been infected by BA.1 and so have immunity to Delta, BA.1 (and BA.2) which would make it difficult for one of the past variants of concern to return to cause a new wave of infection. Incidentally, I have seen some data from Penny Moore that suggest that BA.1 immunity may not be as good against some of the other variants of concern in unvaccinated people. Regardless, BA.1 has probably generated enough immunity to prevent a new wave with BA.1 or BA.2. But what about BA.4 and BA.5? Alex Sigal is a miracle worker in the lab – he has already produced data from his live virus assay – he grew BA.4 and BA.5 in his lab. He tested the serum of vaccinated and unvaccinated people who got infected with BA.1 to see if the BA.1 immunity neutralised live BA.4 and BA.5 viruses. His answer is available in the preprint on slide 7. Vaccinated people who had BA.1 breakthrough infection have good neutralisation of BA.4 and BA.5 – so, we can expect only a few BA.4 or BA.5 infections in this group. In unvaccinated people who had BA.1 infection, they have reasonable neutralisation of BA.4 and BA.5 in their blood but much less than the levels we see in vaccinated individuals. So, we can expect some BA.4 and BA.5 infections in unvaccinated people who had BA.1 infection (like children who do not yet qualify for vaccination) – more than we will likely see in vaccinated individuals. But, in both instances, the number of new BA.4 and BA.5 infections will likely be quite limited in those who had BA.1 infection a few months ago.