Elderly and vulnerable people must get their booster jabs if a rise in Covid cases in the UK is to be prevented, the prime minister has said, as he warned of “storm clouds” forming over parts of Europe. Germany, Austria, Slovakia and Croatia are among countries that have recently seen a surge in Covid cases, with the former recording its highest coronavirus case numbers since the start of the pandemic. Speaking in a broadcast clip, Boris Johnson said the situation was of concern. “I’m seeing the storm clouds gathering over parts of the European continent. And I’ve got to be absolutely frank with people: we’ve been here before. We remember what happens when the wave starts rolling in,” he said. The World Health Organization’s Europe head, Hans Kluge, has said a lack of uptake of Covid vaccines is behind the increase. While Johnson noted that cases in the UK had been “drifting down for a while”, he said it was unclear if the trend was set to continue. “I’m looking at what’s happening overseas, and I’m simply saying to the British people … this is the moment to get your booster,” he said. After coronavirus restrictions were lifted in England over the summer, infection levels rose: by October the UK was experiencing one of the highest case rates in Europe. While figures still remain high, daily case data and the latest figures for infection levels from the Office for National Statistics suggest there has been a fall, with the latter revealing an estimated one in 60 people in the community in England had Covid in the week ending 6 November – about 925,400 people. That is a decline since late October, when one in 50 people in England were thought to have a Covid infection. A drop has also been recorded in Wales, although in Scotland the rate of people testing positive has remained level and the trend is unclear in Northern Ireland. While the decline in England was seen in all age groups and in most regions of the country, it appears the trend is strongest among older children. However, the question remains whether infection levels will rise again now schools have returned from recent half-terms, or whether – as some have argued – growing levels of immunity in children could mean a peak has been reached. “With a marked decrease in infections among secondary school children in England, the half-term break may have played a part, though infections were decreasing prior to this time,” said Sarah Crofts, the head of analytical outputs for the Covid-19 infection survey. “Over the next few weeks we will see if this decline continues.” The situation is far from clearcut. The ONS survey records existing and new infections, whether symptomatic or not. However, people can test positive for some time, meaning changes in the ONS data lag behind the daily reported cases – which are based on those who have come forward for testing – by about two weeks. The latter suggests cases may be showing signs of rebounding, at least to some degree. While daily reported cases in the UK showed a decline during the second half of October and early November, they had risen for four consecutive days, reaching 42,408 on Thursday. On Friday 40,375 new Covid cases were reported in the UK. Prof Rowland Kao, an epidemiologist at the University of Edinburgh, said the recent rise in cases tied in well with a return to schools, but the situation remained in the balance. “Whether or not the [rise] represents a sustained increase, is of course difficult to tell. Vaccinations and boosters continue to be rolled out and with ever-increasing levels of natural immunity as well, it could still go either way,” he said. Prof John Edmunds, an epidemiologist at the London School of Hygiene and Tropical Medicine, who sits on Sage, said half-term was always going to have a big effect, adding that cases were now at roughly the same level, or a little lower, in most regions and nations of the UK than two weeks or so ago – before the half-terms. However, there are exceptions, such as Scotland where cases still appear to be climbing. Edmunds said such a pattern would be expected if the epidemic was left to peak naturally, as has largely been the case. “It should be stressed, though, that a natural peak will be much more drawn out than a lockdown-induced peak, so I would expect to see high rates of infection, hospitalisations and deaths for many weeks – or even months – yet,” he said. Dr Vishal Sharma, the British Medical Association’s consultants committee chair, said the NHS was already overwhelmed. “There’s no doubt that patients are not receiving the standard of care they should be from a fully functioning health service and if more isn’t done to protect the NHS, we risk taking an already fragile recovery backwards,” he said. “The government says it will only act when the NHS is at risk of being overwhelmed. Our members – doctors working on the frontline – are clear that this is not just a risk, but it is happening right now”