Prof Salim Abdool Karim Weekly COVID-19 UPDATES

24 February 2022

The cases in South Africa continue to decline to quite low levels of transmission (Slide 3), despite BA.2 becoming the dominant variant and causing outbreaks when schools opened in January. I think we may get a second uptick in cases when Universities open full-swing with students moving back into residences, unless they have high vaccination coverage.

It took quite a while for the Omicron wave to reach the trough but it is now in a comparable situation to what South Africa had in the first 2 waves (slide 4). This is reassuring and supports the considered lifting of some restrictions. Also reassuring is the continued sharp decline in cases globally (slide 6).

One indicator that is not following the past trends is the test positivity rate (Slide 8), which should have been below 5% by now, as it was at this stage in the past waves. I think the higher than expected test positivity rate may be due to the unusual situation we have now with widespread rapid testing, where positive tests need to be reported (Covid-19 is a notifiable condition in South Africa) but negative tests are not reported and so are not in the database, thereby artificially raising the test positivity.

Today, the Deputy Director-General of the Department of Health, who is in charge of the vaccine rollout commented in the Sunday Times on the challenges in raising the vaccination coverage. Vaccination coverage is just under 50% with at least one vaccine dose and 43% of all adults fully vaccinated (slide 9). Looking across the provinces, it is the 2 most populous provinces – Gauteng and KwaZulu-Natal where vaccination rates are well below par. A lot more needs to be done in these 2 provinces to address this situation. So, what should be done? There is no clear answer to this.

Among the suggestions to address the low coverage was to provide financial incentives for vaccination. In New York, you can get $100 to get vaccinated. So, do these financial incentives work?  In a randomized controlled trial (Slide 10) of just over 8,000 participants in Sweden, a $24 incentive did little to improve vaccination uptake – increasing vaccine coverage by just 4%. The impact of financial incentives may be different here in South Africa, but the Swedish experience does not provide much hope that financial incentives will solve this. To move the needle significantly in increasing vaccination coverage in any country, it will need everyone to pitch in, help and contribute – it is not realistic to expect the government to do this on its own without support from community organisation, NGOs, etc. Everyone has a responsibility to help increase vaccination coverage.

One of the important steps to improving vaccination coverage is to make vaccine proof a requirement for certain activities, especially indoor situations. So far in South Africa, this is being done in some workplaces only – it should become a requirement to go indoors in any place of worship, any office complex, shopping mall, etc. ie. going to indoor activities should have proof of vaccination.

Several days ago, I provided you with a set of slides on the 8 benefits of vaccines. Today, I am sharing with you even stronger empiric evidence for the community benefits of vaccines. In this study from England published in this week’s NEJM, 146,243 contacts of 108,498 index patients were tested. 54,667 (37%) were PCR positive (slide 11). When compared to infection rates in the contacts of unvaccinated people, infection in contacts of people with 2 doses of Pfizer had a much lower infection (68% lower) rate, regardless of their own vaccination status and the benefits were present regardless of variant. This is really impressive!!

The AstraZeneca vaccine also prevents secondary infections but is somewhat less effective. It is noteworthy that the prevention of secondary infections diminishes over time, but some level of  protection remains after 2 Pfizer doses. The prevention of secondary cases is higher for Pfizer than AstraZeneca. The Pfizer vaccine does better for both alpha and delta variants. Well, if anyone wanted evidence that vaccination protects unvaccinated contacts at home (or university residence) or at work / educational institution – here is some solid evidence. Universities without vaccination requirements should note that 2 doses of Pfizer could substantially reduce the risk of viral spread on campuses and in residences.

This level of protection for both alpha and delta has broader implications as it suggests that a high enough vaccination coverage level may provide a substantial community benefit – similar to what is described as “herd immunity”. Since we use mostly Pfizer vaccines in South Africa, we are well placed to draw on this community benefit. The challenge is maintaining the benefits with time. Perhaps a future vaccine may provide long-term antigenic stimulation to maintain high antibodies levels. This could be achieved by using replicating vectors like AAV, which is already being studied at present.

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