Watch: Prime Minister announces Covid-19 winter plan
Boris Johnson rejected a recommendation from his scientific advisors to introduce Tier 4 lockdown measures.
Minutes from a Sage meeting on 11 November and published on Monday reveal that advisors said it is “likely that some localities may need a tier 4 to prevent the epidemic from growing”.
Tiers or local alert levels were implemented in England from 12 October.
The tier system depended on test positivity rates, especially in older or more at-risk age groups, as well as hospital admissions and occupancy.
On Monday, the prime minister announced a return to the stricter “three-tier system” which will be rolled out across England on 2 December, when the second lockdown ends.
More areas are set to be placed in the higher tiers – high risk or very high risk – after lockdown.
But apparently, Johnson did not heed the advice of his scientific advisors on implementing Tier 4.
The paper, entitled Statement on tiers in England and other measures in the Devolved Nations, was published just after the prime minister announced his COVID Winter Plan - which did not include Tier 4 measures - to parliament.
It suggests a Tier 4 would “guarantee” a reduction in prevalence, the proportion of a particular population found to be affected by a disease at one time.
It says: “Tier 3 restrictions, taken as a whole, are associated with slowing growth rates.
“Estimates of the relative reduction in R from tier 1 to tier 3 range from around a quarter to a half. It is therefore unclear whether baseline tier 3 restrictions alone would be sufficient at a regional or national level to reduce R below 1.
“It is likely that some localities may need a tier 4 to prevent the epidemic from growing. A tier 4 that guarantees a reduction in prevalence would be required in most places, if the prevalence is to be reduced.”
The statement said that the implementation of firebreak lockdowns in Wales and Northern Ireland, and the introduction of local protection levels appear to have led to recent decreases in estimates of R-rates.
Wales underwent a “firebreak” national lockdown, also known as a “circuit breaker”, which began on 23 October and lasted until 9 November, with everyone in Wales required to stay home.
The idea behind a “firebreak” is to drastically reduce social mixing, while not inflicting more damage on the economy by prolonging tiered restrictions.
The first minister announced that 11 local authority areas across central and western Scotland, including Glasgow, will enter the highest tier restrictions, which will end on until December 11.
The statement also says that the test and trace system, including mass testing, is most effective when the number of cases are low but that Tier 4 needs to be considered for parts of the country where Tier 3 is not enough to shrink the epidemic.
It says: “Even the most effective test and trace system will have little impact when caseloads are high.
“Given that the impact of tiers will vary depending on the characteristics of different areas, a tier 4 needs to be considered for those parts of the country where tier 3 is not able to shrink the epidemic.
“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.”
Watch: What does the Oxford vaccine announcement mean for the population?
In August, the Department for Education published a four-tier structure, in which all educational institutions would be shut.
Professor Chris Whitty, the chief medical officer, have warned in the past that Tier 3 restrictions were unlikely to be enough to bring down the R rate alone.
Coronavirus: what happened today