Collective immunity to COVID-19? It won’t happen, what then?

Any idea that COVID-19 was going to last just a few months was very misplaced in 2020. Especially after it was recognized that the SARS-CoV-2 virus had spread widely through the air, there was every indication that it would cause repeat damage. episodes of waves. This is what happened during the flu epidemic of 1918.

Additionally, very few scientists predicted that we would see the type of mutations that would occur in such a short period of time. This allowed the virus to become both more transmissible and more able to evade immune responses.

The evolution of the virus has been so rapid that the Delta variant, which currently dominates the world, is at least twice as transmissible as the ancestral virus which circulated.

This means that collective immunity is no longer a discussion the world should be having. We should start to avoid using this term in the context of SARS-CoV-2, because it will not materialize – or it is unlikely to materialize – in our lifetime.

When politicians and others talk about collective immunity, unfortunately, they mistakenly think that the current tools at our disposal are adequate to eliminate the virus. This is not what we have on hand at the moment.

Instead, we should be talking about how to live with the virus. The enormous success that is materializing with COVID-19 vaccines allows us to do so, without actually entering the collective immunity threshold.

The peddling of the concept of collective immunity creates a misconception that we are actually going to come to a point where this virus is going to be eliminated. This is unlikely to happen. It will continue to circulate.

There are a number of dangers in continuing to make people believe that it is possible.

First, it could undermine confidence in vaccines. Even if South Africa meets its target of 67% of the population vaccinated – as reported by the Department of Health – there will still be outbreaks of COVID-19.

The result will be that people will start to doubt the benefits of getting the vaccine. Additionally, for the now dominant Delta variant, immunity to infection (not just COVID-19 disease) would have to be closer to 84% for the “herd immunity” threshold to be met.

Second, failing to face the reality that collective immunity cannot be achieved will mean countries like South Africa will continue to believe that the current restrictions will get them there. It will jeopardize people’s lives on several fronts, including education and livelihoods.

What is collective immunity?

Collective immunity is when a person infected with the virus will not infect, on average, another person. Thus, you reach a state where the immunity of the population to infection with the virus is such that there are too few people in the environment for continued transmission to occur to others.

This is because they have developed immunity to the infection, or at least developed immunity to the extent that even if they were infected, they could clear the virus very quickly and could not pass it on to others. other people. .

So, herd immunity essentially means that you have caused an absolute disruption in the chain of transmission of the virus in the population in the absence of other interventions that could also interrupt the transmission of the virus, such as wearing face masks.

But some changes have forced a shift in our thinking about collective immunity. It is now seen much more as an aspiration rather than an actual goal.

What changed

First, the evolution of the virus and the mutations that have occurred.

A set of mutations made the virus much more transmissible or infectious. The Delta variant is one example. Initially, we thought the reproduction rate of SARS-CoV-2 was between 2.5 and 4.

In other words, in a fully susceptible population, each infected person would on average infect about two and a half to four other people. But the Delta variant is at least twice as transmissible. This means that the Delta variant’s reproduction rate is probably closer to six rather than three.

The second change is that the virus has shown an ability to have mutations that make it resistant to antibody neutralizing activity induced by past infection with the original virus, as well as to antibody responses induced by most. current COVID-19 vaccines.

The third big problem concerns the durability of the protection. Our memory responses currently last at least six to nine months. But that doesn’t mean they’ll protect us from infection with evolving variants, even though such memory responses help alleviate the clinical course of the infection leading to less severe COVID-19.

The fourth problem preventing us from reaching a collective immunity threshold anytime soon is the inequitable distribution of vaccines around the world, slow absorption and slow deployment. Unfortunately, this provides fertile ground for the continued evolution of the virus.

No country is going to lock its borders forever. This means that the entire world population must reach the same type of threshold at around the same time. Currently, only 1% of the population in low-income countries has been vaccinated. And 27% of the world’s population.

With the Delta variant, we would need to ensure that nearly 84% of the world’s population develops protection against infection (in the absence of non-pharmacological interventions) in as short a time as possible.

Next steps

The only lasting solution is to learn to live with the virus.

This will require ensuring that the majority of individuals, especially adults, and especially those at higher risk of developing severe COVID-19 and dying, are vaccinated as quickly as possible. In my opinion, this could be achieved in South Africa with 20 million people vaccinated – not the government’s target of 40 million. But the 20 million should include 90% of people over 60 and 90% of people over 35 who have co-morbidities.

If South Africa reaches this milestone, it could return to a relatively normal way of life, even if the virus continues to circulate and cause an occasional outbreak. It would also ensure a threshold that ensures its health systems are not overwhelmed and people die in large numbers.

We’re just going to have to familiarize ourselves with the idea that SARS-CoV-2 will be like one of the many other viruses that circulate and cause respiratory illness every day. Usually mild infections, and less often severe illness.

So, unfortunately, people will continue to die from COVID-19, but certainly not to the extent seen in the past 18 months. A major advance would be that COVID-19 is not more serious than what is observed in each influenza season (10,000 to 11,000 deaths) in South Africa.

The British experience is the direction in which we should be heading. It comes down to a relatively normal lifestyle, provided we have an adequate number of people vaccinated, and especially people who are at a higher risk of developing severe COVID-19.

The UK currently has nearly 85% of adults who have ever received at least a single dose of the vaccine. As a result, they are able to remove almost any restriction.

The UK is seeing an increase in the number of cases of the Delta variant. But they have seen very minimal changes when it comes to hospitalization and death. The vast majority of people (97%) who still end up hospitalized and die from COVID-19 in the UK are those who have decided not to get the vaccine.