What is "herd immunity? Is it a possibility for fighting coronavirus?
Over the past few weeks, Prime Minister of the United Kingdom, Boris Johnson, seemingly revealed that the UK would adopt a different strategy to fight against COVID-19. The government would no longer try to track and trace the contacts of every suspected case, and it would test only people who are admitted to hospitals and ask elderly people to stay at home. Since the virus causes milder illness in younger age groups, most would recover and subsequently be immune to the virus. Therefore, the UK manages was hoping to achieve herd immunity across the nation by allowing the virus to make its way through the population.
However, Is "herd immunity" a possibility for fighting coronavirus? Before this article goes any further, let's define this term first.
What is herd immunity?
According to The Independent, when enough people in a community are vaccinated against a disease, this can make it more difficult for the disease to spread to susceptible individuals who have not yet been or cannot be vaccinated. This, the NHS outlines, is called “herd immunity”.
The Vaccine Knowledge Project at Oxford University uses the analogy of a person being infected by measles in detail to explain it. “If someone with measles is surrounded by people who are vaccinated against measles, the disease cannot easily be passed on to anyone, and it will quickly disappear again,” the organization states.
However, the organization stresses that herd immunity “only works” if the majority of a population has been vaccinated against a condition, adding that it “does not protect against all vaccine-preventable diseases”. “Unlike vaccination, herd immunity does not give a high level of individual protection, and so it is not a good alternative to getting vaccinated,” the Vaccine Knowledge Project says.
Professor Paul Hunter, a professor in medicine at the University of East Anglia, adds that "The relationship of the proportion of people that are immune that you need to prevent an epidemic varies from infection to infection,” he outlines.
“With something like measles that is very infectious, you need something like 90 percent of people immune, but with other infections, you can get away with much less.”
Is herd immunity a possibility amid the coronavirus outbreak?
On Tuesday 3 March, a statement released by the World Health Organisation (WHO) said that while many people around the world have developed immunity to seasonal flu strains, the same cannot be said for the coronavirus.
“Covid-19 is a new virus to which no one has immunity,” the statement read. “That means more people are susceptible to infection, and some will suffer severe disease.”
During an appearance on BBC Radio 4’s Today show on 14 March, WHO spokesperson Margaret Harris stated that as “we don’t know enough about the science of the virus” and “it hasn’t been in our population for long enough”, scientists cannot yet be certain of “what it does in immunological terms”. “Every virus functions differently in your body and stimulates a different immunological profile,” Ms. Harris said.
“We can talk theories, but at the moment we are really facing a situation where we have got to look at the action.”
According to The Independent’s health correspondent Shaun Lintern, there is currently “no chance of herd immunity with coronavirus”.
“As a brand new virus, no one has immunity to it, so every human being is susceptible to the virus,” he explains. “Herd immunity will only come into effect once a huge majority of people have had it and survived so their bodies create antibodies to the virus.”
Lintern“affirms that in order to achieve “a good herd immunity”, approximately 90 to 95 percent of the population would need to have recovered and become immune to the infection, such as in the case of measles, which could subsequently result in a rise in the number of deaths and people in intensive care.
“There is also a risk coronavirus becomes seasonal and like the flu will mutate each season and therefore again herd immunity can’t come into play.”
However, as the coronavirus is “not well-studied” as of yet, “we don’t know how protective the antibody response is long-term, we don’t know how long it lasts, we don’t know any of these things”. “But it is a reasonable expectation that people who have recovered from infection do have some degree of immunity to subsequent infection,” Professor Woolhouse says.
He adds that herd immunity would be more likely to happen if we were to experience “an uncontrolled epidemic”. However, as there are “lots of measures being put in place to stop that happening”, this could reduce the likelihood of herd immunity occurring.
Source: The Independent/ the Atlantic