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Dr Raghib Ali is a Clinical Epidemiologist at the University of Cambridge and an Honorary Consultant in Acute Medicine at the Oxford University Hospitals NHS Trust.

With ‘Freedom day’ finally upon us, the government once again finds itself under fire from both sides – being simultaneously accused of unethical recklessness/a ‘let it rip’ strategy by some and excessive caution/a ‘zero Covid’ strategy by others.

Both accusations are wide off the mark for the reasons I outline below. There are sound scientific reasons to proceed with step four now – but with caution – and the Government needs to get the messaging right on this to maintain public confidence and maximise the benefits of step four while minimising its harms, and to ensure that we avoid a return to restrictions later in the year.

Aside from a small but vocal minority, most scientists accept that ‘Zero Covid’ is impossible and that Covid-19 will become an endemic disease, that we will have to learn to live with it, and that there must be a time when we will lift all restrictions. The only question really is when?

Because the Delta variant is so transmissible, and vaccines are not a hundred percent effective in reducing transmission, it’s likely to be impossible to reach herd immunity – whereby eventually everyone will become immune – either through infection or vaccination.

(Of course, the higher the proportion that are immune, the harder it is for the virus to spread – and so the UK is in a much better position than other countries with over 90 per cent of adults having antibodies due to a combination of extremely high levels of vaccine uptake in older age groups and natural infections in under 40s.)

An exit wave is therefore inevitable and every country will have one when they finally lift restrictions – including Australia and New Zealand. No country will be able to keep its borders closed forever.

The size of this wave is determined by the number of people who are not immune from vaccination or natural infection. And, once everyone who wants to take the vaccine has been offered it, that’s not going to be reduced significantly by waiting (particularly as the JCVI has not yet recommended vaccines for children). In short, future infections, hospital admissions and deaths are no longer being prevented, just postponed.

And although we are not quite there, the potential benefit of delay is now marginal – in contrast to the situation four weeks ago, when I backed a delay. All those at high risk of hospitalisation and death (i.e. over-40s) have had the opportunity to get both doses (and all adults, one dose) which is why a delay doesn’t reduce hospital admissions and death. Even for infections, the second dose in 18-40 year olds is unlikely to make as much difference as vaccine effectiveness is double that of over-40s for the delta variant.

(This may be due to a better immune response in younger people and also because this age group are most likely to have been previously infected and so their first dose acts more like a second dose.)

And there are some clear advantages of proceeding with step four now, with school holidays reducing the number of contacts and seasonal factors reducing viral transmission. It is better to have the exit wave when the most vulnerable have the highest levels of protection, as they do now. The value of booster doses is still unproven and uptake is uncertain so our defences from vaccination are now likely to be as strong as they will ever be.

As the CMO outlined last week, the modelling shows that all dates lead to similar outcomes for infections, hospital admissions, and deaths. Some models even show outcomes could be worse if step four is delayed to the Autumn due to seasonal factors and the NHS being under even greater pressure from other respiratory viruses including influenza (which is likely to be much worse this year due to people having less pre-existing immunity as there was almost no flu last year.)

The impact of Covid-19 on the NHS is of course something I am well aware of and we are undoubtedly under great pressure now (June was the busiest month ever for emergency departments) with high levels of sickness. But this pressure will not decrease in the coming months and may get worse – and so again, a delay does not help.

‘Long Covid’ is also a valid and important concern and vaccination does reduce it as it reduces infection. However, even if a delay could be shown to significantly reduce the burden of long Covid (which is uncertain) that still needs to be weighed against the health harms which would arise from ongoing restrictions, be that worsening mental health or unemployment.

The final concern relates to new mutations arising due to high prevalence of infection in a partially vaccinated population. But again once you have reached the vaccination uptake ceiling, this will happen whenever step four is taken.

So those who want to continue with restrictions should be honest with the public: that not opening now means delaying indefinitely.

Given all the above, some are understandably asking why caution and continued guidance are still required?

The main consistent finding shown by the various SAGE models showed that if everyone returned to their pre-pandemic behavior/number of contacts quickly (within one month) this could lead to very significant pressure on the NHS approaching that of the first wave (when it would again be difficult to maintain all services causing significant indirect health harm to all other patients and increasing waiting lists further). The peak is much smaller, however, if this happens over three months. This doesn’t reduce overall admissions but spaces them out – i.e. we are back to ‘flattening the peak.’

This is clearly not a zero Covid strategy, but is aiming to be a ‘flu strategy’. This makes sense now given the infection fatality ratio of Covid with our levels of vaccination is similar to flu, and society has been willing to accept that restrictions are not required for flu.

The key remaining uncertainties are the number of contacts people will return to (and how quickly) and the exact levels of vaccine effectiveness. If both of those are ‘worse’ than expected, it is possible that the NHS will come under such great pressure that restrictions will need to be re-introduced.

And that is why it is essential that viral spread is kept under some control through good public health messaging on the need to continue to follow the guidance and why the test, trace and isolate system is still needed (about a third of those who self-isolate go on to develop Covid-19 symptoms) for now while we work our way through this exit wave and cases start falling again.

In many ways,  this approach is similar to the plan I outlined last year when I thought vaccines may be years away and I advocated for mainly voluntary measures and a focus on personal responsibility, as this would lead to more sustainable compliance (especially with indoor household mixing and self-isolation) while reducing other health harms.

Since then, we have seen that people can be trusted to take personal responsibility for themselves and others and will choose the responsible course of action (e.g. over Christmas when contacts didn’t increase overall and polls now show that a large majority of people will continue to wear masks.) And as with previous waves, there are also already signs (from Google mobility / shopping data and so on) that people are changing their behaviour as cases increase.

Finally, it is important to stress that Covid is far from over and that while today is an important and necessary step towards freedom, with freedom comes the responsibility to continue to be considerate and protect others for all of our benefit.