The government's chief scientific adviser has warned the future situation of COVID-19 in the UK is "quite uncertain".
Sir Patrick Vallance admitted that waning immunity and the public's behaviour will be the main factors that decide if the country sees further spikes in cases.
“Nobody is really clear which direction this is going in, but they are clear about the two big variables that could change that," he told BBC Breakfast.
“One is waning immunity; so if immunity wanes faster than expected, you’ll see a bigger increase, and that’s why it’s so important to get booster shots going in the vulnerable and the elderly in particular.
“The second is the behavioural change, how quickly we return to pre-pandemic behaviours… if you aggregate the models, most are saying: ‘Actually, it looks fairly flat, don’t expect the very big peaks we’ve had in the past, it looks fairly flat, but at a very high level at the moment.’"
Adding: “So, the high level remains a concern and from a high level you can go up quite quickly.”
Watch: Climate crisis: People need to change their diet and flying habits to help planet, chief scientific adviser Sir Patrick Vallance warns
The government is anxious about waning immunity and has introduced a booster programme, which is forming a key part of their strategy to avoid the reintroduction of draconian social distancing measures this winter.
Experts have expressed concern about the steep rise in case numbers over the last month, however in recent days there are signs infection levels may be tapering off and declining.
Vallance was asked whether 40,000 COVID-19 cases a day was an acceptable figure; 43,941 were reported within a 24-hour period on Wednesday along with 203 deaths.
"Well, that’s a societal question," he said.
“There are high levels, and those high levels, of course, translate into levels of hospitalisation, but the levels of hospitalisation are very much reduced by vaccination.
“The lower the levels [of COVID], the better in terms of overall overall outcome, but there are costs and consequences of decisions in both directions there."
Earlier this month the UK recorded the second highest number of infections in the world, and it is at odds with many of its European neighbours over social distancing measures like mandatory face masks in certain settings.
The NHS Confederation has called on the government to implement its "Plan B" strategy to tackle COVID, which would involve the reintroduction of mask wearing, guidance on working from home, and vaccine passports to enter certain venues – warning that the NHS risks being overwhelmed.
However, the government has insisted there is not yet evidence the NHS would come under "unsustainable" pressure under current measures.
When it comes to the long-term, Vallance warned that the virus was here to say but hinted the infection will become less severe.
“I will say though – and it’s an important point to make – that, as this infection becomes gradually becomes endemic, it will occur year on year, we will see this circulating every winter, I suspect, in particular," he said.
“And so, gradually, as immunity builds, the protection will be there, the consequences will be reduced, but we’re not not there yet.
"We’ve still got, clearly, people going into hospital, it’s still a significant risk.”
The UK reported 43,941 coronavirus cases on Wednesday, with the total down 4% from the previous seven days. It also reported 207 deaths.
Watch: Boris Johnson 'confident in steps taken' as winter approaches