The UK remains vulnerable to another wave of coronavirus infections once restrictions are eased – in spite of the ongoing success of the vaccine rollout – the government’s chief scientific adviser has warned.
As Downing Street unveiled its roadmap out of lockdown, Sir Patrick Vallance insisted that a slow and gradual reopening is the best approach for avoiding a dangerous resurgence of the virus across Britain.
In terms of the prevalence of infections, he insisted that the UK is in “a not very good position” but admitted the situation was “getting better”.
The government’s staged proposals for lifting the lockdown measures have been informed by a series of modelled scenarios produced by experts at the University of Warwick and Imperial College London.
The modelling takes into account a number of “uncertain assumptions” about the progress of Britain’s immunisation programme and the trajectory of the epidemic, including: the real world effectiveness of the vaccines against severe disease and infection; vaccine coverage and rollout speed; behaviour factors; and the impact of easing restrictions.
Summarising the findings compiled by the government’s Scientific Pandemic Influenza Group on Modelling, Operational sub-group (SPI-M-O), Sir Patrick said many vulnerable people are predicted to remain susceptible to Covid-19 in the months ahead.
This is because either they won’t have received a jab or their vaccination has not prevented them from being infected and falling ill, SPI-M-O said.
Previous scientific modelling, released last month, suggested that even with an uptake rate of 90 per cent among the UK’s top priority groups, up to 1 million at-risk people would remain vulnerable to the disease.
This may be enough to fuel another wave of hospitalisations and deaths if restrictions are lifted too quickly, potentially burdening the NHS for many more months to come.
“Vaccines are predicted as you'd expect and hope to make a big difference but even with high vaccine levels, and indeed quite a high vaccine coverage, it's important to remember that a large number of people in the population remain unprotected,” Sir Patrick said during a media briefing on Monday.
According to a SPI-M-O summary, even with 79 per cent coverage of all adults in the UK, only 62 per cent of the population would be vaccinated.
“As the vaccines do not completely prevent transmission, the reduction in transmission that results would be expected to be lower than 62 per cent,” it adds.
As such, Sir Patrick warned that a faster reopening of society would lead “to a much bigger increase” in infections across the UK.
“The more vaccine you can get out across people, the better it will be,” he said. “But it’s likely you get an increase in cases when you start to open up. That’s likely.
“Exactly when that occurs and exactly how high the numbers are, it's not possible to be precise.
“The sooner you open up everything, the higher the risk of a bigger resurgence. The slower you do it, the better.”
Sir Patrick pointed to Israel where despite high vaccination rates “you're seeing an increase in hospitalisation amongst younger people . . . because they’ve got the older people protected, which is encouraging in terms of vaccine efficacy, but it tells you what you potentially see if you have a big epidemic before you've got everybody vaccinated.”
Under Britain’s phased lifting of restrictions, each stage will be reviewed every four to five weeks, allowing scientists and the government to compile and assess the relevant data before making any new decisions on the course out of lockdown.
“Because we don’t know for sure what the effects of the different measures are, do the steps with enough time between them that you can measure data,” Sir Patrick said.
Pausing to assess the effect of each change was the only way in which Boris Johnson could be sure his route out of lockdown would be irreversible, he added.
Sir Patrick said there were also uncertainties surrounding the effectiveness of the vaccines, what proportion of the population will eventually be covered, what baseline measures (such as mask wearing or social distancing) will be needed in the long term, and the effects of the different seasons.
Because of this, SPI-M-O is much more confident in its modelled outcomes up to the end of May than beyond then.
“The message that comes out of all this modelling is start from a low baseline, so try and get numbers down before releasing, go slowly, [and] go in blocks that you can measure the effect of after four or five weeks,” Sir Patrick said.
After initial hope that the vaccines would restore some degree of normality by spring, the latest science indicates that the UK still has some way to go in bringing the epidemic to an end.
However, SPI-M-O says that further resurgences of the virus could be kept “well below” the level of those seen in January 2021 if a gradual approach to easing restrictions is adopted, the vaccines are rapidly rolled out and longer-term baseline measures, including an effective test and trace system, remain in place.
"Relaxing measures later therefore has two benefits; it allows prevalence to be brought down further, and also allows more people to be vaccinated before R (reproduction number) increases,” the group said in its summary.
"The combined effect of these means a significantly smaller resurgence."
But even in a cautious scenario, a further 58,200 deaths from Covid-19 are estimated up to June 2022, according to the Imperial College modelling.
One of the main concerns expressed among the government’s scientists is a failure among the public to comply with the rules as more and more people are vaccinated.
Professor Dame Angela McLean, deputy chief scientific adviser, said she feared that “people won’t adhere so faithfully because they think vaccines are going to prevent everything”.
“The other issue we're really worried about is uptake won't stay at the current very high levels. We need uptake to stay very, very high in order to minimise the amount of transmission,” she said.
Dame Angela added that there was a risk of the virus seeping into “older and more vulnerable” populations if coverage isn’t high enough among people who don’t typically get sick from the virus, such as the young.