‘Tier 4’ may be introduced if Tier 3 doesn’t work, Sage experts warn

The current national lockdown is set to end on December 2, with the country moving into a “tougher” version of the previous three-tiered system, Boris Johnson announced on Monday.

However, a Sage scientific advisory panel has separatedly suggested that Tier 3 areas may need to move into a new “Tier 4” where restrictions are failing to adequately stem the spread of infections.

In documents released today, the panel stress that Tier 1 measures alone “are not enough to prevent the epidemic from growing rapidly” and tougher restrictions are significantly more effective.

During a meeting dated November 12, Sage members concluded: “Tier 2 is the minimum intervention required to maintain any degree of control on transmission.

“Though this would not be the case in all places and there is significant uncertainty.

The added: “In most cases moving from Tier 1 to Tier 2 would slow growth rather than reverse it.”

A separate Scientific Pandemic Influenza Group on Modelling, Operational sub-group (SPI-M-O) statement, dated November 11 suggested a “Tier 4” may be required in areas where Tier 3 restrictions are not reducing numbers.

It read: “There is a great deal of uncertainty about the effect of tiers, particularly Tier 3.

“Test and trace, including mass testing, is most effective when prevalence is low.

“Even the most effective test and trace system will have little impact when caseloads are high.

“This is particularly important in the run-up to the winter festive period if relaxation of measures is under consideration. Keeping incidence flat or decreasing between now and then is crucial.”

Sage set out that it is unclear whether baseline Tier 3 restriction alone would be sufficient at a regional or national level to reduce the Covid R rate below 1.

The November 12 documents said: “It is almost certain that prevalence will remain high in some parts of the country at the end of the current national restrictions.

“When policymakers plan transitions from national measures to a localised approach, or between tiers in future, consideration will need to be given to both prevalence and growth rate of new infections.”


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