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Variants, the fourth wave, vaccines and the unlikelihood of herd immunity

- The Scientists Collective

What might happen in South Africa?

The rise of the scary-sounding variants, a South African third Covid-19 wave that was much worse than the first or second for most of the country, and the introduction of multiple vaccines has confused many of us. Uncertainty about the future is always frightening. This is especially so when scientists don’t explain things clearly, or where there is disagreement around ideas like ‘herd immunity’, whether the new variant makes you sicker than the previous ones, and speculation about how the virus will evolve further.

First, some key points in our article (below) about SARS-CoV-2 (the virus)/Covid-19 (the disease) in South Africa:

  • South Africa, like much of the African region, has experienced a devastating third wave, made worse by the very small number of people who were vaccinated when the super-infectious Delta variant arrived.
  • The phrase “herd immunity” is used incorrectly by senior advisers to government, and unfortunately has entered popular vocabulary among politicians, commentators and the media, when it is extremely unlikely to occur.
  • Ongoing mention about vaccinating to reach herd immunity threatens to undermine messaging on the actual value of vaccines, which is primarily to prevent severe disease and death.  
  • Our immune system seems unable to stop SARS-CoV-2 infection in everyone, even after vaccination or previous infection.
  • However, the vaccines (and immunity produced by a previous infection) seem excellent (not 100%, but very close) at stopping severe illness — the kind that puts you in hospital and kills you.
  • Understanding that the primary role of Covid-19 vaccines is to protect against severe disease and death helps us to decide how best to use current vaccines, future possible combinations or “boosters”.
  • A better understanding will also better inform how we use masks, and apply social distancing and lockdowns, to get our society, schools and other institutions back to normal as quickly and responsibly as possible.
  • Experts are cautious about firmly forecasting the future of the Covid-19 pandemic as there are many uncertainties. But we know if a fourth wave arrives towards the end of the year (as previous waves have been roughly five to six months apart), vaccinations for as many people as possible are our #1 priority, as well as preparing and stocking health facilities, and ensuring safeguards against rapid spread are in place in places where people gather in large numbers. Lessons need to be learnt from the experience of the first three waves.
  • In the short term, it is impossible to over-emphasise how important it is to get the vast majority (90% or more) of vulnerable people (those over 60, and those with comorbidities) vaccinated before November 2021.
  • Deal with it! Masks and physical distancing are here to stay until there is high penetration of Covid-19 vaccines among the groups most vulnerable for severe Covid-19.
  • If we get the majority of adults vaccinated, (like the 88% of adults in the UK), especially the most vulnerable, there is a future (maybe a year away) where we may be able to get back to a normal lifestyle and start regarding this virus like the seasonal influenza virus — something that we have to live with and manage.


In this article, we try to explain the current scientific understanding, and, more importantly, some scenarios that may evolve as we stare down a fourth wave, and how you should plan your life.

But first, a few concepts:

What is ‘herd immunity’? (and why is it unlikely to materialise for SARS-CoV-2) 

Herd immunity, simply put, is where even individuals without immunity enjoy protection from an infectious disease because so many people around them have immunity (either from prior infection or vaccine), and do not transmit the infection, in this case the coronavirus SARS-CoV-2. While the unPC term “herd immunity” makes us sound like a bunch of animals rather than humans, it’s become a popular phrase used in the media and by scientific advisers quoting it alongside statistical formulas, which mislead and falsely reassure the public and policy makers alike.

So let’s unpack the term so we know what we mean when we use it in this article.

The term herd immunity, sometimes called population immunity, has been around for about 100 years, and implies we can protect the vulnerable from infection by getting immunity in the people around them, enough to mean they are unlikely to be exposed.

It was rapidly applied to SARS-CoV-2 in early 2020, with some scientists, politicians and other real and self-proclaimed experts advocating that a more or less uncontrolled spread of the infection was a way to get society back to normal. This is a reckless approach in our view.

The reality is that herd immunity does not apply to SARS-CoV-2. This is because the virus is very widespread, highly infectious, and mutates relatively easily. As a result of its characteristics, people who have been vaccinated or infected can still get infected and spread the virus, meaning everyone will get the virus eventually.

SARS-CoV-2 is a coronavirus; several different coronaviruses are widely circulating among human beings, causing mostly common colds every year. Every person reading this article has had infections with these coronaviruses dozens of times in their life, their immune system primed for repeat challenges when they had their first infections during the early years of life.

Everything we see about SARS-CoV-2 suggests it will do the same with time — simply become one of the circulating viruses causing mild illness that we all deal with every season. The current dreadful illness mainly occurs in those with older or compromised immune systems who have not encountered this virus before, although we are seeing significant severe illness even in younger populations.

Organisms always evolve towards greater transmissibility, though the effect on virulence (the ability to cause harm) is much less clear — virulence can decrease even as transmissibility increases.

Developing full-blown herd immunity for SARS-CoV-2 would require either an evolution in the virus against its own “interests” (infecting as many of us as possible), or a level of immunity as yet unseen from the currently available vaccines; we think both are scientifically improbable.

So, we can’t have herd immunity and shouldn’t use the term. 

We strongly suggest advisers to government or politicians stop using this term, as it creates a misleading idea of what to expect with Covid-19 in the future, and risks creating doubt about the value of vaccines. Perhaps a better term is “population effective protection’’ — how many people have been vaccinated or infected in the population and enjoy protection from severe illness (but not necessarily infection).

This makes it easy to see why vaccines are our only solution out of the pandemic without old and vulnerable people getting sick and dying in large numbers. It also makes it easy to understand that future “booster doses’’ or changes in the pattern of vaccine administration may be needed.

If immunity reduces over time or proves insufficient, for example in immunocompromised people, we may need further jabs (as with flu), or we may find that a certain combination of vaccines confers optimal or even life-long protection against disease. Some people may not need these add-on vaccines — the circulating virus may act as a natural booster, after an initial vaccine or infection.

There is a fortune of research going on in the field of booster vaccine doses — watch this space.

Protection from Covid is available, one way or another. Get it through the vaccine rather than natural infection! 

In a substantial proportion of people, especially the elderly and those with comorbidities like diabetes, but sometimes even in younger and otherwise healthy people, the virus unleashes a serious immune reaction that damages the lungs and other organs. Natural infection seems to be much less severe when you are younger, but it is still bad enough for public health experts to recommend vaccination (this is partly because the vaccines are very safe when compared to the unpredictable risk of developing severe Covid).

We also don’t yet know what the long-term consequences of long Covid will be, which can affect any age group. Natural infection will come your way eventually, but this may be much later than your vaccination date, so by waiting for natural infection you won’t be able to stop the spread of the disease through the population.

Bottom line: getting infected is ultimately inevitable if you engage with other human beings — and being vaccinated when that time comes provides you with maximal protection. Getting protection from illness from a vaccine is very, very safe compared to getting it from experiencing SARS-CoV-2.

Variants are often more infectious:

Viruses mutate as a natural phenomenon, so the news that this happened is not surprising to scientists.  Everyone has heard of the “South African’’ (now named “Beta’’) and the current “Delta’’ variants, and there are others from Brazil and the UK.

So-called “variants of concern”, either have mutations that confer advantage in evading our immune response and/or transmit more easily than the original version of the virus — in the second wave, the Beta variant was responsible for the vast majority of infections in South Africa. In the third wave, the Delta variant caused massive waves of infection in Africa, Europe, Asia and North America. It is inevitable that further variants will still develop.

The variants vary as to how lethal they are or how sick people get. It is important to remember that viruses are not necessarily out to kill you — the goal of any living organism is to reproduce, and so a virus will do this by infecting as many people as possible to spread as far as it can. Your immune system is designed to try to stop or limit the infection before it damages the body.

Vaccines are a wonder of modern science. Even the ones that do not fully prevent infection.

There are actually only three questions we need to ask, concerning how vaccines work: do they protect you from infection? If not, do they stop you getting sick? And finally, will they make you less likely to pass infection along if you get infected?

To the first question, the answer is “mostly” — the virus is less likely to cause infection in the vaccinated, certainly less symptomatic infection, although the variants have shown that some vaccines may be better than others at this.

Should we worry that several of the vaccines are not as good at preventing infection?

Every current vaccine significantly reduces the chances of hospitalisation and death (and probably long Covid) remarkably well. Currently, in some cases, vaccinated individuals do experience what health professionals call “breakthrough infections”, where the virus finds its way past the body’s initial defences, and illness occurs (usually it feels like a cold), but the rest of the immune response will prevent any spread and severe harm.

Indeed, this kind of partial protection is likely to happen eventually with ALL the current crop of vaccines. We do not need to worry about this, so long as the vaccines continue to prevent the serious consequences of Covid-19.

This is excellent news — none of us lives in fear of the common cold apart from germaphobes.

Finally, will it prevent transmission?

Preliminary data suggest there are fewer people infected in households where more members are vaccinated. This makes sense, as people who are vaccinated tend to shed less virus when they get infected. However, it has been shown that the Delta variant makes you shed far more virus than other variants.

The research question here is critical to us getting back to normal society — does being vaccinated make you less infectious to others? Again, too early to know for sure. Watch this space, but we are hopeful.


Will there be a fourth wave, and when?

Frustratingly, this is not clear. We are guessing any time from October/November, because it seems to be following a cyclical pattern in many places, every six months, here and elsewhere. But the surges in different places, even between South African provinces, vary widely, with the peaks differing by two to three months, as well as in severity.

Many countries, like ours, had a worse second and far more intense third wave; others have had two waves but with high levels of infection in between, and in some, the second wave wasn’t as bad. Portugal had a third wave just a few weeks after the second. India’s third wave was devastating. So, wait and see and be prepared. In highly vaccinated countries, almost all the deaths are in unvaccinated people, which is why South Africa should single-mindedly focus on this.

So, what scenarios await us? Based on the understanding we have of SARS-CoV-2 so far (set out above) we have detailed some possible scenarios below:

Scenario 1 (and the one we think most likely)

The infection becomes more like a common cold or like seasonal flu.

After several further epidemic waves, the virus continues to circulate indefinitely in a series of smaller waves, infecting people (vaccinated and unvaccinated) repeatedly every year or two, like the other circulating human coronaviruses. We may see more major waves if a new more transmissible variant similar to Delta emerges, but it is likely the most transmissible versions are fighting it out (keep an eye on the Lambda variant in South America).

For people with prior infection or who have been vaccinated, every subsequent infection means on average less severe illness. For instance, a first infection can range from no symptoms at all, to a severe illness putting you in hospital or to giving you long Covid (which we explained in a previous article) after even initial mild infection, but subsequent infections are less and less severe.

Why do we think this scenario is possible?

Large studies, including in health workers, show that once you have had it the first time, subsequent infections are almost always far less severe. We see the same with vaccines — when you get infected, it’s usually minor or asymptomatic. Some people still get sick the second time, but severe illness is very unusual. There is a theory (read here) that this is how one of our endemic coronaviruses arose, in the 1890s — it surged through the world, killed lots of people, and those who survived developed immunity and thus adapted to it.

What are the implications of this scenario?

Paradoxically, this is the happiest scenario, but ONLY with mass vaccination. If we don’t quickly vaccinate a large number of people who have not been infected yet, then the elderly, and those with comorbidities in particular, will still be at risk of severe illness and death.

Some poorly thought-through commentaries have called for “natural infection’’ to accelerate this process, arguing that getting as many young people infected as possible will speed us towards herd immunity. If the scientific scenarios above are valid, this is a dreadful option, as herd immunity in the context of Covid-19 is such flawed thinking. If they are wrong and we are right, and this is allowed to happen, a huge number of people will get sick (even young people have a small chance of severe illness), potentially have chronic illness (long Covid), and die for nothing.

In summary, it’s a race: you get the virus or you get the vaccine. If you gamble on the virus, as some anti-vaxxers will, you put yourself and others at risk of all the Covid-19 consequences, and if lucky, will survive and be immune. You will also put others at risk, even if your own infection remains without symptoms or runs a mild course. If you get the vaccine, you fast-track your immunity at a far lower risk of illness.

Immunity to SARS-CoV-2 may prove to be transitory, and reduce to next to nothing over a few years, much like with flu. With flu, getting the disease or getting the vaccine protects you, but immunity is lost quickly, which is why we have to vaccinate annually. The best-case scenario is that natural infection or vaccines provide permanent protection; the “flu’’ scenario the worst, and again there are variations where we may have to “boost’’ in more vulnerable populations every so often.

We think that if the above scenario is in play, and mass vaccination occurs quickly, we can be back to almost or total normal within a year, provided 80% or more of adults are vaccinated. In this scenario, vaccinated or previously infected people can probably congregate as normal, with little or no restrictions.

Until large numbers of people are infected or get vaccinated, though, and we see that subsequent infections are shrugged off like the common cold, the masks and physical distancing will need to stay — to protect the unvaccinated. There are variations of this scenario, where the virus mutates to a more benign form, or even spontaneously disappears (we think this is highly implausible), or we get a super-vaccine that totally protects from repeat infections (also unlikely)  — but means the same thing — life gets back to a normal.


Scenario 2: Not much changes 

The virus continues to circulate indefinitely, evolving as it goes to escape our efforts at becoming immune, and continuing to cause lots of severe disease as it’s doing now. We think this is not likely because both natural and vaccine-derived immunity would have to fail to be significantly protective against severe disease for the new variants, and that’s not what we’re seeing. Our immune system is incredibly sophisticated, and the virus likely has a limited number of options of evading it while causing severe disease.

Scenario 3: Eradication

We include this here, even though as we explain above, we think this scenario is frankly impossible.

Some commentators continue to advance an eradication/control option. In this scenario, lockdowns, public health interventions and contact tracing with aggressive quarantining brings the virus under control to the point of eradication, as they have done in New Zealand and Iceland. This isn’t feasible since society is then perpetually vulnerable to having the virus run through its immunologically ill-prepared population and undoing all your hard work (see Australia at the moment).

Obviously, eradication would be ideal, but the level of societal change required, especially in the context of a global travel network and porous borders, combined with the fact that the seeding of the virus is so widespread (and rare patients continuing to excrete the virus for months), that it seems incredible. As we describe above, herd immunity approaches to eradication using infections and vaccines are impossible.

We are aware we are putting our heads on the block with these scenarios somewhat, but South Africans need to start thinking about the possible futures that await them and prepare for these different scenarios. The health, economic and social costs that the pandemic has had on our society have been exacerbated by inadequate strategy and poor planning. We also need to understand why vaccines are critical to any normal future, including reviving our economy. If the vaccines continue to work as well as they have, a vaccinated future holds hope of a return to normality.


The following scientists have contributed to this article:

Prof Shabir Madhi, Respiratory and Meningeal Pathogens Research Unit, University of Witwatersrand; Dr Jeremy Nel, University of Witwatersrand; Prof Marc Mendelson, University of Cape Town; Prof Lucille Blumberg, National Institute of Communicable Diseases; Dr Nomathemba ChandiwanaDr Samanta Lalla-EdwardsTaylor JohnsonProf Francois VenterHolly FeeDr Chelsea KrugerDr Karlien MollerDr Simiso SokhelaDr Joanna Woods, all of Ezintsha, University of Witwatersrand; Dr Regina Osih, The Aurum Institute; Prof Glenda Gray, Medical Research Council; Prof Yunus Moosa, Department of Infectious Diseases, UKZN; Prof Wolfgang Preiser, University of Stellenbosch; Prof Lucy Allais, Department of Philosophy, University of the Witwatersrand; Prof Shaheen Mehtar, University of Stellenbosch; Prof Vinodh Edward, The Aurum Institute; Dr Fareed Abdullah,  SAMRC and Steve Biko Academic Hospital; Prof Imraan Valodia, Faculty of Commerce, Law and Management, and Director of the Southern Centre for Inequality Studies, University of the Witwatersrand; Dr Aslam Dasoo, Progressive Health Forum; Prof James McIntyre, Anova Health Institute; Prof Eric Decloedt, University of Stellenbosch; Prof Colin Menezes, University of the Witwatersrand; Prof Guy Richards, University of the Witwatersrand; Dr Jantjie Taljaard, University of Stellenbosch; Prof Morgan Chetty, KZNDHC and IPA Foundation.

This article was first published in Daily Maverick/Maverick Citizen.