Science Advisory Group Says the Effects of Ending COVID Restrictions Are 'Uncertain'

Peter Russell

July 13, 2021

The effect on hospital admissions of ending COVID-19 restrictions on July 19 in England is "highly uncertain", experts have said.

The latest summary by the Scientific Pandemic Influenza Group on Modelling (SPI-M) said the aftermath would be dependent on "unknowable factors" that included how the public responded to the end of lockdown over the next few weeks.

Rising Hospitalisations

Prof Matt Keeling/SMC

However, Matt Keeling, professor of populations and disease at the University of Warwick, said the significant easing of lockdown in 6 days' time was "very likely to lead to over 1000 hospital admissions per day at the peak, and probably around 10,000 people being in hospital at that time". Experts from the group stressed that the Government should have contingency plans in place to respond if hospital admissions soared to the point of threatening the smooth running of the NHS.

"The public is going to control which of the trajectories we're on," predicted Prof Keeling. A combination of vaccine uptake and public behaviour would determine whether "we see a very large wave, or do we see something that's much more flattened", he told a briefing hosted by the Science Media Centre.

"So far we have not lived in a country without restrictions for the last 18 months, and the current variant that is circulating is also much more transmissible than the variants that we had last year, or indeed the one that we had at the start of the epidemic," cautioned Anne Cori, lecturer in infectious disease modelling at Imperial College London.

Summer Infection Rate 'Extremely High'

Among other main findings of SPI-M, a sub-group of SAGE, were that:

  • Very small changes in assumptions on vaccine effectiveness and behaviours after July 19 would lead to very large differences in infection trajectories

  • The peak of the summer resurgence of SARS-CoV-2 infection would be lower if people did not suddenly abandon precautionary behaviour, resulting in a wave partially shifted to the autumn and winter

  • The peak in mortality would be lower than that seen in January 2021

  • Prevalence of infection would remain "extremely high" for the rest of the summer

  • The "best estimate" for the R number in England was between 1.2 and 1.5

Prof Graham Medley/SMC

Asked whether there was scope for a further rise in the SARS-CoV-2 infection rate after step 4 of the roadmap out of lockdown, Graham Medley, professor of infectious disease modelling at the London School of Hygiene & Tropical Medicine, said: "I think the simple answer to that question is yes, especially because, you know, the vaccines are not perfect, and we are not vaccinating everybody. And so, there is room for another wave of infection."

A third of the population in England was currently susceptible to the Delta variant of SARS-CoV-2, first identified in India, the group concluded.

"We think there's been about 15 million infections in total, ie, about 27% of the population, and together with vaccination, we'd estimate that this leads to about a third of the population still susceptible to the Delta variant," said Prof Keeling.

That would lead to increasing hospitalisations and mortality after July 19, he said.

Group Urges 'Gradual' Unlocking

Prof Keeling added: "I think what we are just really stressing is that, however we open up and whenever we open up, this has to be a gradual approach, simply because there's this … nature of the system that if we suddenly change behaviour, you get a much, much larger epidemic than if we allow things to move gradually."

Prof Medley told the SMC briefing that he expected the country to achieve herd immunity "one way or another", defined as a reproduction number of around 1.

Commenting on the predictions, Dr Thomas House, reader in mathematical statistics at the University of Manchester, said that the modelling "shows the potential for a significant additional wave of hospitalisations and deaths", but also "considerable uncertainty in what the most likely scenario is".

He added: "As we have seen at several points in the pandemic, the potential of factors such as hospitalisations and deaths to grow exponentially – meaning that they double after a certain number of days – means that such a new wave can quickly cause significant problems from a relatively low baseline. 

"Therefore, as the statement suggests, it is likely to be a good idea to have a plan in place for such an eventuality, while hoping that it does not come to pass."

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