England will face a resurgence of coronavirus cases before Christmas if the country returns to the tiering restrictions in place last month when the latest lockdown is over, government science advisers have warned. The concern was raised in a consensus statement released on Friday in a batch of documents prepared by the outbreak modelling subgroup of Sage, the government’s expert advisory committee. The consensus document, signed by modelling teams around the country, warns that while an initial analysis found the most stringent tier 3 restrictions had a “noticeable impact” on transmission, it was unclear whether the measures were sufficient to drive the pandemic into decline. Scientific advisers called in September for a two-week “circuit breaker” and other interventions to contain the pandemic, three weeks before the prime minister announced the three-tier Covid alert levels. Immediately after the announcement, Prof Chris Whitty, England’s chief medical officer, conceded that the most severe tier 3 restrictions would not be enough to drive the R below 1, although extra local interventions were meant to be added to the baseline measures. The R figure reflects the average number of people a person infected with coronavirus passes the disease on to. Figures released by the Office for National Statistics (ONS) on Friday confirmed that the rate of increase in coronavirus infections has slowed across England, while according to Sage R remains marginally above 1, meaning the pandemic continues to grow. In its latest estimates, Sage reported the number of new cases was growing by 1% to 3% per day in the UK. Written the day before the second lockdown came into force on 4 November, the consensus document goes on to warn: “The longer-term outlook depends on both the nature of non-pharmaceutical interventions that are implemented in England after 2 December and policies over the festive period. If England returns to the same application of the tiering system in place before 5 November, then transmission will return to the same rate of increase as today.” Science advisers fully expect the lockdown to push R down over the remainder of the month, meaning that England should start December with fewer daily infections. If people adhere strictly to the lockdown rules, R should drop below 1, signalling that the pandemic has started to shrink, the consensus states. If sustained until 2 December, the number of hospitalisations and deaths would be expected to fall until at least the second week of December before they start to rise again, it adds. But further measures beyond the tiers imposed before lockdown were expected to be necessary in December to prevent cases from rising again. According to the statement, even the top-level restrictions may not do enough to keep infections under control. “Initial analysis shows a clear effect from tier 3 interventions and much less from tiers 1 and 2. It is not yet clear whether tier 3 measures alone are sufficient to reduce the reproduction number below 1,” the document states. Speaking before lockdown, Whitty said the tier system may need to be modified to make it more effective. That could involve tougher recommendations for the extra measures applied on top of the tier 3 baseline restrictions, or moving more regions into tier 2 or 3. Advances in mass testing may also help, advisers believe. New models of the pandemic for the next six weeks which appear in the consensus statement show that without the November lockdown, daily hospital admissions may exceed those in the first wave by the start of December. By pushing R down to 0.8, the models suggest hospitalisations would fall steadily until the second week of December. The latest estimate from Sage puts R between 1.0-1.2 for the UK and 1.1-1.2 for England, both down from 1.1-1.3 the week before. The numbers reflect the pandemic over the previous weeks, given the time lags in the range of data used. That means the apparent slowdown is driven less by the November lockdown than the restrictions in place before. According to the ONS, about 1 in 85 people in the community in England – about 654,000 people – had coronavirus between 31 October and 6 November 2020, with about 47,700 new cases per day, although this does not include cases in settings such as universities or care homes. The previous week the survey suggested 618,700 people, or one in 90, had the virus, with a similar number of new cases per day. But there were reasons for concern. The ONS figures mask stark variations in infection rates among different age groups. Among older teens and young adults, who bore the brunt of new infections after the summer, the proportion of those testing positive has fallen. In under-35s, infections seemed to be levelling off. But in older age groups – those most vulnerable to the virus – infections were still climbing. “Positivity rates continue to increase in those aged 35 years and over and are now above 1% among those aged 35 to 49 and 50 to 69 years,” the team writes. It will be some weeks before any slowdown in the spread of the disease, or even a potential future shrinking of the pandemic, is seen in the death toll. Paul Hunter, professor of medicine at the University of East Anglia, said it was too early to know what drove the surge in new infections reported on Thursday. But he warned that if the rise was caused by people socialising more in the week before the new restrictions came into place, it could reduce the benefit of the lockdown.