The ‘collective immunity’ route to fight the coronavirus is unethical and potentially dangerous – Health

As most of the world tries to suppress the spread of the coronavirus, some countries are doing it alone, trying to control the pandemic through so-called “collective immunity”.

Herd immunity means allowing a large number of people to contract a disease and therefore develop immunity to stop the spread of the virus.

The Netherlands reportedly plans to use collective immunity to combat the coronavirus epidemic, just as Britain is withdrawing from such plans after warnings that it could lead to 250,000 deaths.

The World Health Organization has criticized a “collective immunity” strategy, which said much greater measures are required. Other health experts say the approach is experimental at best and dangerous at worst.

So can collective immunity protect us from the coronavirus, and should countries adopt it?

First, let’s understand immunity

Our bodies fight infectious diseases like the coronavirus through our immune system. The body produces antibodies in response to intruding organisms to fight and eliminate them.

Once the body has fought a disease, it retains a “memory” of the germ and how to fight it better and faster next time.

Once a person has developed immunity to a virus, they will probably not get it again. The theory behind herd immunity is that once many people develop immunity to a virus, it will eventually stop spreading to people who have not yet contracted it.

Reduction of numbers in the collective immunity

Collective immunity is essentially a numbers game.

It is all based on the basic reproduction rate, in other words, how many new infections each case will generate.

A rate with a value of 1 would mean that one person can pass it on to at least one other person. The higher this number, the more infections in that case. So, to finish the spread, this number should drop below 1.

The reproduction rate of the coronavirus is between 2 and 3.

As the infection spreads, the group of susceptible people shrinks as more immunity develops. Herd immunity aims to reduce the number of susceptible people to the point where the reproductive rate falls below 1 and the spread of infection is stopped.

For measles, 95 percent of people need to be immune for the infection to stop. For the coronavirus, I estimate this figure to be around 40%, based on a 2.6 reproduction rate. So if around 60 percent of people are immune to the infection, this is enough immunity to stop the spread of the coronavirus.

(There have been a few reports of people infected with the coronavirus twice, but they have not been based on peer-reviewed research, so it can be ruled out for now.)

So is collective immunity a good plan?

At first glance, a crowd immunity strategy may seem wise. But the absence of a coronavirus vaccine means that you are at very high risk.

The best way to rapidly develop collective immunity is through vaccination. A vaccine delivers a small amount of virus to the body, and the immune system learns to fight it without having to get sick. But we don’t have a coronavirus vaccine yet.

If vaccines are not available and the infection spreads, some people will develop a mild version of the disease and recover. But it is dangerous and unethical to trust this method to fight the disease.

First, the medium and long-term consequences of the coronavirus are not yet known. And second, although some people are not severely affected by the disease, under a collective immunity strategy, they could still transmit the virus to older people who are at high risk of dying.

Expert analysis found that creating collective immunity in the UK would require more than 47 million people to become infected. With a death rate of 2.3 percent and a severe illness rate of 19 percent, this could lead to the deaths of more than a million people and the need for critical care for another eight million.

What should we be doing?

Let’s say Australia and New Zealand relied on collective immunity. Now let’s assume, conservatively, that 10 percent of the population was infected – 500,000 New Zealanders and 2.5 million Australians. For a short period, those numbers would disastrously overwhelm the nations’ health systems.

The safest public health strategy is to prevent the occurrence of coronaviruses at all costs. This would buy the health system time, “flattening the curve” so that hospitals were not inundated with cases all at once.

That is why it is so important to control movement across our borders, impose self-isolation, restrict public meetings, track contacts of existing cases, and isolate those with the virus. Australia and New Zealand are now essentially following these steps. It may also be advisable to screen passengers at departure terminals for signs of the virus and perform tests when necessary.

It is also essential to educate the public about safe hygiene and ensure the supply of disinfectants, hand sanitizers, safe food, soap and water, as well as access to services when needed. Now is also the time to take special care of our elderly.

With these measures in place, we give ourselves the best opportunity to put the coronavirus genius back into the bottle as soon as possible, and minimize the number of deaths.

***

Arindam Basu is an associate professor of epidemiology and environmental health at the University of Canterbury.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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