Leading up to lockdown on the 23rd March, the Government and its Scientific Advisors made two significant mistakes.

The first was to decide on the 12th March that the virus was transmitting at such a rate within the community, that contact tracing was no longer feasible.

Whilst this was a correct assessment at the time, it was one spawned out of a long-term lack of planning within Whitehall for a virus of this kind. Despite two major coronavirus outbreaks since the turn of the century, the UK had continued to focus on preparing for a flu pandemic. In the event of a major flu outbreak, contact tracing would be largely ineffective. Add to this a Government that took until April to promise any significant increase in testing capacity, and thus it was clear contact tracing would not be possible in the U.K.

In February, Public Health England informed SAGE that current testing capacity would only be able to ‘manage 5 new cases a week, tracing 800 contacts’. Between 28th Feb and 29th March, 1,356 separate incursions of Covid-19 are estimated to have come from abroad alone.

Secondly, the Government misjudged how prevalent the virus was, and how quickly it was spreading. This was, in part, a result of not being able to test sufficient numbers. On the 20th March, Government modellers suddenly undermined earlier assumptions. They informed COBRA that cases were doubling every 3-5 days, not 5-7, and that the reproduction rate was higher than the 2.4 previous models had been based on.

It was these errors that helped lead to lockdown. In the face of a virus, still largely unknown, and with no accurate knowledge of its spread, the Government was forced to shut down the country. The public understood the need for such a drastic policy response, helped by the way countries from east to west had helped legitimate its worth. They also sympathised with the Government, appreciating how unprecedented the situation was.

Neverthess, at its heart lockdown represented the last line of defence, when all other possible interventions had failed. The failure of the UK’s initial defences was understood in March, they may not be again.

Over the summer, the Government had time to increase testing. And yet this morning, it is reported that ministers are still unsure over the spread of the virus, increasingly relying on hospitalisation figures rather than cases, due to testing failures.

The resurgence of the virus was not unexpected either. On analysing China’s lockdown in February, Imperial College London informed SAGE that when “measures are lifted a second peak can be expected”.

When discussing the possibility of enforcing the following measures in combination – closing schools, home isolation of symptomatic cases, voluntary household quarantine, and social distancing – SAGE agreed that they “reduce r to 1” but then “result in a second large epidemic once lifted”. As a result, SPIB would “prefer a subset of measures which would have a more moderate impact, avoiding a second wave”.

The verdict was clear. According to official documents, “SAGE was unanimous that measures seeking to completely suppress Covid-19 will cause a second Peak”.

It is for these reasons that a second lockdown would be seen as such a failure. The resurgence of the virus over the winter was expected. There has been time for the Government to improve its armoury, and thus having to rely on its last line of defence again, will be met with greater criticism.

A solution to avoiding a second national lockdown , can be found in some of the proposals discussed by SAGE during February and March.

The answer is essentially months of restrictions being periodically tightened.

A paper prepared by the London School of Hygiene and Tropical Medicine, reveals a scenario where restrictions are implemented each time a certain number of ICU cases are recorded.

London School of Hygiene and Tropical Medicine

In the second column, the ‘cocooning of the elderly and self-isolation’ is implemented for seven months. In the third column, an aggressive, short term (3 week) lockdown is triggered when ICU services are ‘stretched’.

In their modelling LSHTM used different triggers for the implementation of the lockdown: 5, 10, 15 cases per week In ICU, and lockdown is in place until incidence is reduced under the threshold.

LSHTM concluded that “periodic aggressive measures added onto a background of social distance measures can mitigate the epidemic, preventing ICU services from being overstretched”. Whilst admitting this would mean “a longer epidemic, lasting perhaps a year”, the overall reduction on the number of cases would be “dramatic”.

Similarly, Imperial College London on the 16th March informed the Government of an “adaptive policy, in which social distancing is initiated after weekly confirmed case incidence in ICU patients exceeds 200 per week”. At this point, additional restrictions are implemented. This would “keep” case numbers “below surge limits”.

Imperial College London

Thus if the months ahead are likely to be a turbelent ride of restrictions being switched on, off and then on again, how does this ever end?

For LSHTM, aggressively following such a policy would eventually lead to a situation where some form of herd immunity is reached.

One of the problems with a population gaining herd immunity though, is that there is ‘overshoot’ – when more people than are required contract the virus. This is because at the point herd immunity is reached – the peak – ‘there is still a very large number of infectious individuals’.

Under LSHTM’s model scenario, drafted in March, vulnerable individuals would be shielded for 7 months. The country would then enforce an ‘aggressive 3-week lockdown’ when ICU capacity is close to being exceeded. During a lockdown, all contacts outside the household would be reduced by 90%.

Overall the epidemic is not allowed to overshoot and the total number of cases is reduced ‘appreciably’. Yet this would involve significant disruption to the economy and daily lives, “that would undermine any perceived benefits from avoiding lockdown”. It would also continue for ‘perhaps a year or more’.

S Riley at ICL however, showed how such a strategy of herd immunity would not be possible to achieve in the UK, because at the moment critical care capacity was exceeded, people’s behaviour would be to stay indoors and reduce contacts. At this stage, not enough people will have been infected with the disease to achieve herd immunity. Thus leaving the country with a broken healthcare system and no immunity amongst the population. ‘Critical care facilities would be saturated quickly and if populations spontaneously reduce transmission when this occurs any possible benefits of attempting mitigation are lost’.

As a result of this difficult, and the possibility of thousands more becoming infected, Imperial College, in their 16th March paper, outlined that a vaccine would be the best way out of such restrictions.

“The major challenge of suppression is that this type of intensive intervention package – or something equivalently effective at reducing transmission – will need to be maintained until a vaccine becomes available (potentially 18 months or more) – given that we predict that transmission will quickly rebound if interventions are relaxed”.

The prospect of periodic restrictions is growing. The Government needs to decide its overall strategy. What will be the UK’s escape route out of this on and off scenario?