Covid-19 Weekly Updates

 

1. BA.2 mini-waves across several countries mimic SA’s trend from 2 months ago

Watching the global trends in SARS-CoV-2 cases (slide 2) is déjà vu. About 2 months ago, I wrote about South Africa’s BA.2 mini-wave (Slide 3) at the tail end of the country’s omicron wave (largely due to BA.1). In Slide 3, you can see the way in which cases went up towards the tail end of the decline in cases – this little “hook” in the way cases were declining only to get a short-lived increase before it continues its decline. This trend has repeated itself in several countries and the global trend mimics what happened in South Africa 2 months earlier – just highlighting the importance of learning from other country’s experiences.

 

2. Trying to Solve a Covid Mystery: Africa’s low death rates – New York Times

We are so fortunate to have some outstanding newspaper articles on Covid-19. One such article was Stephanie Nolan’s article in the NY Times on the enigma of the low reported death tolls in Africa – has Africa really been spared the pandemic deaths? In slide 11, I have summarised new hot-off-the press preprint (not yet peer-reviewed) that makes 2 important points:

a) Officially reported Covid-19 deaths in Zambia are only 4,000 but the country has >80,000 excess deaths over the first 2 pandemic years. The Zambian excess death per population ratio is similar to the rate of excess deaths in South Africa! Yet, its reported deaths suggest a country largely spared the ravages of Covid-19.  

b) Covid-19 PCR testing of corpses in the Lusaka morgue, indicate that identification of Covid positive patients in grossly under-estimated. Over 2 years, about one third of corpses tested positive, while only one tenth of those tested prior to death were positive, suggesting that testing is only picking up a small fraction of those infected. About 90% of corpses tested positive during the wave peaks, few being identified before they died.

As I said in the Times article (slide 11), there is no reason to think that any African country has been spared mortality, especially in their elderly. Due to the continent’s younger population, the actual number of deaths is lower but age-specific Covid-19 death rates in the elderly are comparable to other countries. But there are still some countries in Africa that seem to have enigmatically low death tolls, as there are in some of the other regions as well.

 

3. Should we just let the virus spread unhindered and focus on reducing severe disease and deaths?

There are some who are now arguing that there is no point in having any public health restrictions in place – because we should just focus on preventing severe disease with vaccines as vaccines cannot reach herd immunity and public health restrictions do not work. The point about letting the virus spread unhindered is similar to the arguments contained in the Great Barringdon Declaration with one major difference in that the declaration was written before vaccines were available. But the declaration essentially argued that the virus should be allowed to spread unimpeded in the population while the vulnerable and elderly were protected in order to get natural-infection driven herd immunity. 

 

Many of my colleagues and I argued vociferously against the Declaration in 2020. In 2021, I discussed the shortcomings of the Declaration in a lecture I delivered at MIT (Slide 12). This was long after the declaration was drawn up and so I drew upon the benefits of hindsight, eg. the writers of the declaration could not have known the SARS-CoV-2 would develop variants that can escape natural immunity. In my MIT lecture, I explained the 5 fundamental fallacies of the declaration. But, the same idea is being promoted again but this time to let the virus spread in the population which has some level of vaccine immunity. 

 

The argument that the public health measures do not work is not true – several trials have shown their efficacy, eg. the Bangladesh trial showed the benefits of masks. Also, public health measures have prevented the usual annual burden of Respiratory syncytial virus (RSV) and influenza in South Africa – in 2020, we had no flu season. There are, of course, differences in trial efficacy and real-world effectiveness due to human behavioural factors, but the measures do work when used properly.

 

On the issue of herd immunity (which the WHO also refers to as “population immunity”), there has been spectacular changes in views by some scientists. For example, on 5 August 2021, Professor x said that “the only way to ‘defeat’ Covid-19 would be to ensure herd-immunity is reached in the country as soon as possible.”  Six weeks later, on 20 September 2021, the same Professor x says “We need to stop talking about herd immunity because it’s not going to materialise with Covid-19. That is not the reason we are vaccinating.” 

 

In reality, herd immunity was always going to be a major challenge as vaccines would have to be highly effective in preventing secondary infections. Information is only emerging now to show that vaccines reduce secondary attack rates by up to 72% (last week’s slides have this information). Whether this is good enough remains to be seen. But the reproductive rate of each new variant of the virus is increasing. Since herd immunity levels rise as the reproductive rate rises, herd immunity gets progressively more difficult to reach as virus transmissibility rises. But there are benefits to be gained from vaccine immunity even well below the levels required for herd immunity, as I explained a few months ago based on the study from Israel that showed reductions in transmissions as vaccination coverage rose at low coverage levels.

 

But the biggest fallacy of this argument is that it does not take into account the effects of the virus in those with asymptomatic, mild and moderate infections. Long Covid (Slide 13) is estimated to occur in about 10%-20% of those infected, regardless of the presence or severity of symptoms of the original Covid-19 infection. One year after infection, regardless of severity, there is a 50% increase in strokes, heart attacks and myocarditis (Slide 14) with significant long-term cardiac effects. A major concern is the neurological effects, which see a loss of up to 2% of grey matter in the brain from Covid-19 infection in those with mild or asymptomatic infection (slide 15). While small losses of brain matter may not have an immediate impact in most of us as we only use a small amount of our brain capacity, in elite US football players (Slide 16), who have to use more brain capacity during matches, there is a 10% reduction in the number of passes (a key performance indicator) they make in a football match. So, preventing infection is important. It may be particularly important in the future as we deal with the long-term effects of Covid-19. 

 

So, preventing severe disease and death is very important but it is also important to try to minimise and slow the spread of the infection generally, choosing measures carefully by maximising those that are effective and feasible but minimise disruption to people’s everyday lives.