What is herd immunity? Why top scientists are calling for new approach to managing Covid-19 - and Great Barrington Declaration explained
Sweden was the only country in Europe that didn’t implement a national coronavirus lockdown
The coronavirus pandemic has largely been handled in the same manner across the world, with countries imposing strict national lockdowns to contain the spread.
The main strategy has been to restrict social contact as much as possible in an effort to minimise the risk of transmission, resulting in social distancing measures, bans on household mixing, and more stringent hygiene practices being introduced across the globe.
In the UK, a national lockdown was in place for almost six months, and brought with it the closure of schools, shops, pubs and restaurants, as well as a ban on international travel.
However, not all countries followed the same approach, with Sweden opting for a different strategy in handling the outbreak.
What did Sweden do?
Sweden avoided imposing a national lockdown in response to the pandemic, instead opting for a largely voluntary approach to guidelines.
It was the only country in Europe not to introduce strict lockdown measures at the start of the outbreak, with scientists believing that such an approach may have helped it to avoid a second wave of infections.
The country only implemented minor restrictions to help curb coronavirus infections, which included simple guidance on social distancing and hand washing, a five month ban on gatherings exceeding 50 people, and asking people over the age of 70 and in vulnerable groups to self-isolate.
However, shops, bars and restaurants were kept open throughout the pandemic, as well as borders, while schools were kept open for children under the age of 16.
The country was initially criticised in the early stages of the pandemic, after recording a spike in mortality rates that was five times that of Denmark, and 10 times higher than both Norway and Finland. However, Sweden has recently seen its average daily deaths drop dramatically, with figures now behind that of 13 countries, including the UK and the US.
It is thought that because many young people in Sweden have now already had coronavirus, it has less chance to spread through the population, suggesting the country may have achieved herd immunity.
Recent studies suggest that an infection rate of 43 per cent may be enough to achieve herd immunity, a figure that is much lower than the previously cited 60 per cent.
What is herd immunity?
Herd immunity is achieved when the vast majority of a population becomes infected with a virus to prevent it spreading.
If such a high proportion of a population have already had the virus, or have become immune after a vaccination, it reduces further spread, helping to protect those who have not yet been infected.
Depending on how contagious a virus is, around 70 to 90 per cent of a population needs to be immune to protect the uninfected and achieve herd immunity. However, recent studies have suggested this figure may actually be much lower.
The threshold differs between illnesses and its level of contagion, with the likes of measles, for example, requiring around 95 per cent of people to be vaccinated to stop it from spreading.
Could Sweden’s approach work in the UK?
While Sweden has attempted to achieve herd immunity, it has come at the cost of thousands of lives.
Statistics have shown that the country had high mortality rates among the most vulnerable, which suggests the same may occur if such an approach was implemented elsewhere, such as here in the UK.
Sweden’s method has come under fire for not being able to successfully protect the vulnerable population, but there have been calls from UK academics to allow those who are less susceptible to the effects of coronavirus to be allowed to return to normal life.
A new declaration, which is earning thousands of signatures from medical professionals, academics and the general public, has called for a herd immunity approach to tackle the pandemic while protecting the most vulnerable populations.
The declaration, named the Great Barrington declaration, has been backed by academics from the universities of Oxford, Nottingham, Edinburgh, Exeter, Cambridge, Sussex, York, St George’s University of London, Strathclyde, Leicester, Queen Mary University of London and the University of East Anglia, among other experts from around the world.
It calls for a herd immunity approach to tackling coronavirus, in which the old and vulnerable are shielded while those who are less susceptible can resume ordinary life.