A winter Covid wave is likely to be mild compared to last year even without "Plan B" measures, government scientists said as they warned that restrictions may not work as well as in previous waves.

       The latest modelling, released on Friday, suggests that unless there is a rapid increase in transmission rates, coupled with the repeated waning of protection from Covid jabs, hospital admissions will be nowhere near the highs of January.

       The Scientific Pandemic Influenza Group on Modelling (SPI-M) team concluded that admission rates "are unlikely to get significantly higher than those currently seen" if vaccine protection does not wane much further than has already been observed.

       Warwick University modelling shows that even if behaviour returns to pre-pandemic norms and the waning of immunity is high, a winter wave would spike at around 1,500 admissions a day – well below the 4,000 a day at the January peak.

       The London School of Hygiene and Tropical Medicine (LSHTM) calculated that even if infections pass 100,000 a day, admissions would peak at around 800 a day, and deaths at around 150 – far fewer than the 1,300 in the winter wave.

       Only a more virulent new Covid variant could push the trajectory into something resembling last winter in the absence of waning immunity, the scientists believe.

       The Telegraph understands scientists have already advised that "Plan B" should be enacted if case rates are to be brought down, but ministers are sticking with their plan to "live with the virus" rather than attempting to suppress it further.

       The Scientific Advisory Group for Emergencies (Sage) is meeting less frequently as the Government attempts to move from a crisis footing to managing the virus as an endemic disease.

       Hospital admissions are now the main focus for ministers, with scientific sources saying the Government is less concerned about case numbers and more focused on making sure the NHS can cope.

       "Our autumn and winter plan always predicted that the cases would rise around about now, and we're certainly seeing that in the numbers," Boris Johnson said on Friday. "We're seeing high levels of infection, but they're not outside the parameters of what was predicted or what we thought we'd see in the autumn and winter plan."

       He said the "key message" for all over-50s was to "think about getting your booster jabs. When you get the call, get the jab".

       The papers published on Friday also reveal that scientists are unsure whether restrictions proposed in "Plan B", such as mandatory mask-wearing and working from home, would have the same impact as in previous waves.

       The Independent Scientific Pandemic Insights Group on Behaviours (SPI-B) said: "Behaviour is likely to be different from what it was when the measures were originally put in place… testing and isolation rules have been relaxed since the end of the roadmap.

       "One-time effects that previously reduced or increased transmission could not be repeated, such as the Euro 2020 football championship and the isolation of a large proportion of the active population during the so-called 'pingememic'."

       The more infectious delta variant is also now the dominant strain, which could alter the impact of interventions, the SPI-B report said.

       Scientists said booster vaccine uptake was crucial in determining whether "Plan B" would be needed, and recommended that the Government encouraged greater use of home testing and gave more support to people needing to self-isolate.

       They said it would be possible to delay "Plan B" until case numbers were doubling every two weeks. Currently, case rates have only risen by about one fifth in the past fortnight and now stand at around 50,000 a day.

       But some experts believe it is time to let the virus spread through the population so it can become truly endemic.

       "That is how severe disease will be reduced in the long term, and how the pandemic will ultimately become just another cause of the common cold," said Paul Hunter, professor of medicine at the University of East Anglia.

       "As the infection is becoming endemic, pretty much everyone, whether vaccinated or not, will be getting repeated infections from now on, so any social distancing measures will not prevent infection, only delay it. Most epidemiologists doubt we will see anything like last winter."

       Warwick researchers also admitted their roadmap modelling had been wrong, writing: "We clearly have not seen the very large-scale outbreaks that were considered feasible in the Step 4 scenarios.

       "Given the large number of infections that have occurred during the summer months of 2021 and the additional amount of vaccine that has been delivered, it is now impossible to reach the highest levels that were projected as worst-case scenarios in the roadmap."