What is herd immunity- and can it stop the coronavirus?

The term 'herd immunity' has been hitting headlines during the coronavirus pandemic. But what is it - and can it help protect us?
  • We earn a commission for products purchased through some links in this article.
  • Last week, the government announced its plan to “delay” the peak of the coronavirus until the summer, when NHS services are under less pressure.

    As part of the delay plan, the government was thought to be considering  ‘herd immunity’ as part of their approach to tackling the coronavirus outbreak in the UK.

    On Friday Sir Patrick Vallance, the UK’s Chief Scientific Advisor, said the aim of herd immunity is to “reduce the peak [of the coronavirus], broaden the peak, not suppress it completely; also, because the vast majority of people get a mild illness, to build up some kind of herd immunity so more people are immune to this disease and we reduce the transmission”.

    However, there has been some backlash against the idea that the UK would be using herd immunity to prevent the prolonged spread of the coronavirus, due to the number of people who would be exposed to the virus.

    Writing in the Sunday Telegraph on Friday, Health Secretary Matt Hancock was quick to clarify the Government’s plan, saying it was “based on the expertise of world-leading scientists”. He added also, “Herd immunity is not part of it. That is a scientific concept, not a goal or a strategy. Our goal is to protect life from this virus, our strategy is to protect the most vulnerable and protect the NHS through contain, delay, research and mitigate.”

    As reported by ITV, one of alternative measures proposed by the Health Secretary Matt Hancock included over 70s staying at home for the foreseeable future to “‘shield’ older and medically vulnerable people from the virus.” Alongside continued self-isolation for all those experiencing flu-like symptoms and rescheduling or cancelling mass gatherings such as sporting and music events.

    What is herd immunity?

    Herd immunity is when a population becomes resistant to a contagious disease. It happens if enough people become immune to the disease that it’s harder to spread, as less people are able to catch it and pass it on.

    The benefits of herd immunity were first realised when it was successfully used to wipe out small pox and whooping cough bacterial meningitis.

    MORE: Stockpiling food: food to stock up on in an emergency

    However in these cases, it was the creation of a vaccine that helped to create full herd immunity . This is also how the tactic of herd immunity has also helped to slow the spread of more common viruses like the flu.

    Unfortunately, we currently don’t have a vaccine for the coronavirus. So, instead it’s thought by those advocating an this approach that through the natural spread of the virus through the population, we will eventually achieve herd immunity.

    How does herd immunity work?

    The more infectious the disease, the more people need to be infected with the disease for herd immunity to be successful.

    For example, measles is highly contagious. Therefore for herd immunity to be effective, 90 per cent of the population have to be immune to the disease. This is why the MMR (measles, mumps and rubella) vaccine is highly advised by doctors.

    Jeremy Rossman, Honarary Senior Lecturer in Virology and President of Research-Aid Networks at the University of Kent, says that in order for us to achieve herd immunity for the coronavirus, we would need 60 per cent of the population to be affected, which is about 47 million people. This is because the coronavirus is less contagious than measles for example, but more contagious than the common flu – which requires 40 per cent immunity in the population to prevent it from spreading.

    He goes on to write in the World Economic Forum that, “Slowing the spread of COVID-19 is a promising strategy, especially when combined with enhanced measures to protect the elderly and those with underlying health conditions. By slowing the spread of the disease, the NHS might have more time to prepare, we might be able to develop treatments or vaccines and we will be closer to the summer when we have lower incidences of other diseases that burden the NHS, such as the flu.”

    This useful diagram from the National Institute of Allergy and Infectious Diseases shows how herd immunity works:

    Will herd immunity work to prevent the spread of the coronavirus?

    According to ITV journalist Robert Peston, the government’s strategy to minimise the impact of the coronavirus “is to allow the virus to pass through the entire population so that we acquire herd immunity, but at a much delayed speed so that those who suffer the most acute symptoms are able to receive the medical support they need, and such that the health service is not overwhelmed and crushed by the sheer number of cases it has to treat at any one time”.

    However, many have criticised the policy to just let the virus pass through the community as an ineffective – and even dangerous – public health strategy. This is because the immunity would be mainly generated in younger people, as they are considered to be capable of handling the virus. So in other words, younger people (aged 20-40) would get the virus, ideally becoming immune and therefore not able to pass it on to anyone older. Naturally, this doesn’t include those younger people with weakened immune systems through conditions such as diabetes.

    The criticism comes as those between the ages of 20 and 40 are also often in contact with those who are vulnerable to the coronavirus. In some cases this will be someone who is caring for a family member, or those who work in healthcare and care homes.

    Essentially, for the short term, the best way to prevent the spread of the virus is to follow the latest guidelines from the NHS.

    MORE: Hand washing video: are you washing your hands properly?

    This includes washing your hands with soap and water often for at least 20 seconds, avoiding contact with people who are unwell and covering your mouth and nose with a tissue or your sleeve when you cough or sneeze.