RESEARCHERS have called for a two-track approach to easing lockdown which would strengthen protection for the most vulnerable but relax restrictions for the majority of the population.

The approach, known as 'segmenting and shielding', has been recommended by a group of scientists from Edinburgh and London including one of the Scottish Government's Covid advisors.

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Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh, said: “Segmentation and shielding recognises that, although social distancing impacts on the whole of society, the public health burden of Covid-19 is concentrated in a subset of vulnerable people.

"By targeting protection to those that need it most, the strategy helps to ensure that the health system is not overwhelmed by severe cases, while giving policy makers greater leeway to partially relax social distancing measures for the majority of the population.”

It is believed to be the first time that 'segmenting and shielding' has been put forward as a major public health strategy. It is better known as a way of 'cocooning' infants through the immunisation of close family members against disease.

The team from Edinburgh University, Imperial College London, and the London School of Hygiene and Tropical Medicine have modelled a range of scenarios to illustrate how different restrictions could be applied to different groups.

They show "the effects on the epidemic curve of a gradual ramping up of protection for the vulnerable population and a gradual ramping down of restrictions on the non-vulnerable population over a period of 12 weeks after lockdown"

Their findings have been made available to the UK and Scottish Governments.

The strategy involves segmenting the population into different risk groups, based on a person’s medical history and potential healthcare needs.

READ MORE: Scotland's death rate from Covid likely to be lower than rest of UK due to lockdown timing

As a result, younger healthy adults and children, as well as over-70s without any ailments associated with an increased risk from Covid, would resume something closer to normal life.

Those most at risk - who currently fall within the shielded category - would continue to stay at home, with the added safeguard of targeted virus screening.

They write: "Intensive screening would, ideally, include daily checks for symptoms, daily tests for virus presence (preferably with results available the same day to prevent pre-symptomatic transmission), regular serological [antibody] testing and monitoring of frequent contacts (e.g. household members) of shielders.

"If too large fraction of the population were to be classified as ‘shielders’ this would quickly overwhelm current testing capacity in the UK.

"Nonetheless, routine rapid testing of shielders could have a significant impact and further increase the scope for relaxing restrictions on the entire population."

Researchers say lockdown restrictions could be eased for most people, as long as sufficient public health measures stay in place to keep transmission rates low.

These would include self-isolation of people with Covid-19, quarantining affected households, contact tracing and voluntary social distancing.

The most vulnerable – the frail elderly and those with underlying medical conditions such as cancer, heart or respiratory diseases – would still need to be shielded from contact with anyone potentially infected with the virus.

To achieve this, people sharing a house with a vulnerable person, care workers and health professionals would need to protect themselves from infection.

However, the risk to the rest of the population could be managed without resorting to lockdown.

Asked about a potential "two-tier approach" to leaving lockdown, First Minister Nicola Sturgeon said policymakers had to weigh up "the fairness or potential unfairness" of any approach.  

"Is it fair? The judgement might be yes, it is, because we can't allow the quest for perfection to be the enemy of good progress. But we have to think about these things.

"None of us want to have a two-tier or a multi-tier society."

The study stresses that the general non-shielding population will continue to be the "main reservoir of infection", therefore surveillance measures to contain the spread of the virus will be essential, say the researchers.

They write: "It is therefore vital that transmission rates are kept as low as possible, even if this population is allowed to exit lockdown.

"Measures including self-isolation of cases, quarantining of affected households, contact tracing and voluntary physical distancing will be necessary to achieve this.

"In all our scenarios the vulnerable segment is subject to increased protection indefinitely. [Segmenting and shielding] is also more likely to succeed if there is less or no relaxation of restrictions on shielders."

They say that contact tracing can include "both traditional and app-based" methods.

However, the researchers caution that not enough is known about the build-up of immunity in affected populations and stress that this aspect of the epidemic needs to be monitored very closely.

Dr Bram van Bunnik, Postdoctoral Research Fellow at the University of Edinburgh’s Usher Institute, said: “Easing the measures taken during the lockdown is important as they currently have a tremendous effect on our society, but this should only be done in a way that is both safe for the people that are most vulnerable as well as for the health and safety of NHS staff.

"Segmentation and shielding is a possible way of achieving this: measures could be eased for a large proportion of the population, however the vulnerable population likely still needs to be protected for a prolonged period.”