Why the spread of the Delta variant shatters hopes of gaining group immunity


Any idea that COVID-19 was going to last for only a few months was very misplaced in 2020.

Especially after it was recognized that the SARS-CoV-2 virus spreads largely through the air.

All indications pointed to the fact that it would provoke spikes in the infection in waves, as it already happened in the influenza epidemic of 1918.

Furthermore, very few scientists predicted that we would see the type of mutations that we have seen in such a short period of time.

This has made the virus more transmissible and with a greater capacity to evade the immune response.

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 original virus.

This means that herd immunity it is an off-table issue.

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We should begin to avoid using that term in the context of SARS-CoV-2, because it will not materialize, or is unlikely to materialize, during our lifetimes.

When politicians and other groups talk about herd immunity, unfortunately, they have the misconception that the current tools we have are adequate to eliminate the virus.

But it’s not like that.

This is why we should be talking about how to live with the virus.

The tremendous success of COVID-19 vaccines allows us to do so, without actually reaching the herd immunity threshold.

Promoting the concept of herd immunity creates the misconception that we are actually going to reach a stage in which we eradicate the virus.

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That is unlikely to happen.

It will continue to circulate.

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

First, could affect trust that you have in vaccines.

Even if South Africa reaches its goal of vaccinating 67% of the population, as set by the Department of Health, it will still suffer outbreaks of Covid-19.

The result will be that people will begin to doubt the benefits of getting vaccinated.

Also, for the now dominant delta variant, immunity against infection (not just covid-19 disease) would need to be closer to 84% for the “herd immunity” threshold to be reached.

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Second, failing to face the reality that herd immunity cannot be achieved will mean that countries like South Africa will continue to believe that the current restrictions will get them there.

That will put people’s lives at risk on multiple fronts, including education.

What is herd immunity?

Herd immunity occurs when someone infected with the virus, on average, does not infect another person.

Thus, a state is reached in which the immunity of the population against infection by the virus is such that there is too few people for continuous transmission to occur.

This is because they have developed immunity against infection, or at least have 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 other people.

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

But some changes have in turn forced a change in the way we think about herd immunity.

Now it is seen much more like an aspiration than a real goal.

What has 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 just an example.

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We initially thought that 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 between two and a half and four more people.

But the delta variant is at least twice as transmissible.

That means the spawn rate for that variant is probably closer to 6 than 3.

The second change is that the virus has been shown to have the ability to have mutations that make it resistant to the neutralizing activity of antibodies induced both by a past infection and by most current vaccines against COVID.

The third major problem centers on the protection durability.

Our responses last at least six to nine months at this time.

But that does not mean that they will protect us against infection from evolving variants, even if such responses help to attenuate the clinical course of infection leading to less severe COVID.

The fourth problem that conspires against our reaching a threshold of herd immunity in the short term is the uneven distribution of the vaccine around the world, the slow acceptance and the slow release. Unfortunately, this provides fertile ground for the continued evolution of the virus.

No country is going to keep its borders closed in perpetuity.

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This means that the entire world’s population needs to reach the same type of threshold at roughly the same time.

So far, only 1% of the population in low-income countries has been vaccinated.

In total only 27% of the world’s population.

With the delta variant, we would need to approach 84% of the world population protected against infection (in the absence of non-pharmacological interventions) as soon as possible.

Next steps

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

This will require making sure that the majority of people, especially adults, and particularly those who are at increased risk of developing severe COVID-19 and dying, get vaccinated as quickly as possible.

In my opinion, this could be achieved in South Africa with just 20 million people vaccinated, half of the 40 million target set by the government.

But the 20 million would have to include the 90% of people over 60 and 90% of people over 35 who have comorbidities.

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If South Africa achieves this milestone, it could return to a relatively normal lifestyle even as the virus continues to circulate and cause occasional outbreaks.

It would also ensure a threshold that ensures that health systems would not be overwhelmed and that people would not die en masse.

We will just have to get comfortable with the idea that SARS-CoV-2 will be like one of the many other viruses that circulate and they cause respiratory illnesses every day.

Usually mild infections and less commonly severe illness.

Unfortunately, people will continue to die from covid-19, but certainly not to the extent that we have seen in the last 18 months.

An important advance would be that covid-19 was not more severe than what is seen in each flu season (and causing 10,000 to 11,000 deaths) in South Africa.

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The UK example

We should turn to the UK experience.

Back to a relatively normal lifestyle, as long as we have an adequate number of people vaccinated and, in particular, that people with a higher risk of developing severe covid are vaccinated.

The UK currently has about 85% of adults vaccinated with at least one dose of the vaccine.

As a result, they can eliminate almost all restrictions.

The country is experiencing an increase in the number of cases of the Delta variant.

But they have seen very nominal changes when it comes to hospitalization and death.

The vast majority of people (97%) who still end up being hospitalized and dying from covid-19 in the UK they are the ones who decided not to get vaccinated.

* Shabir A. Madhi is Dean of the Faculty of Health Sciences and Professor of Immunization at the University of the Witwatersrand, South Africa. He is also director of the Research Unit for the Analysis of Vaccines and Infectious Diseases of the SAMRC, University of the Witwatersrand.

This article originally appeared on The Conversation. You can read the original version here.


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