A third lockdown for England was inevitable. Pressure on the NHS is growing as it deals with new infections from a variant of the coronavirus that scientists estimate is 50-70% more transmissible. New infections continue to climb past 50,000 each day, and daily deaths are in the hundreds. A few weeks ago, many felt optimistic that vaccines could return England to normal by the spring. Instead, it seems we are entering a dangerous new chapter of this pandemic.

It’s easy to feel frustrated by the government’s response to this pandemic, and wonder why it hasn’t acted sooner. Ministers wasted an opportunity to suppress the virus in the summer when cases were low, and instead chose to open up quickly and recklessly after the first national lockdown. The government subsidised people to eat out in restaurants and bars, and encouraged holidays abroad via “travel corridors” without any kind of testing or quarantine restrictions for when travellers returned.

It was always likely that, if uncontrolled, the virus that causes Covid-19 would mutate. High prevalence created more opportunities for a variant to emerge that now appears to be spreading at a worrying pace.Where does this leave the UK? Among scientists, optimism about several approved vaccines is tempered by serious concerns about the new variant, and what the next weeks have in store. Sage experts note that even with restrictions in place, it will be a challenge to stop the spread of this new variant over the next few weeks.

Several fringe scientists have argued that this builds a stronger case for the government to allow the virus to spread through younger, healthier members of the population. Aside from the opportunities this would create for more mutations to emerge, new data from Manaus, Brazil, shows just how catastrophic an uncontrolled epidemic would be.

An estimated 76% of people have been exposed to Covid-19, and the epidemic is still continuing. Applying age-specific infection fatality rates from Manaus, a 76% attack rate would mean 350,000 deaths in the UK and 1.58 million deaths in the US. Manaus has a particularly young population, so the fatality rate is likely lower there than it would be in the more elderly demographics of western Europe and North America.

The substantial rate of serious illness associated with Covid-19 also underlines the risks of exposing a large percentage of the population to a virus that is still not fully understood. Even a plan to allow the virus to run through the population would require restrictions, because the high rate of hospitalisation that results from Covid infections is dangerous to everyone.

If hospitals are full, patients of all stripes – whether they’re suffering from a heart attack or a road traffic injury – can’t get the necessary treatment. And without spare beds, Covid-19 patients can’t get access to the ICU care they need to stay alive.

The opposite response to this is what has been called a maximum suppression or “zero Covid” model. But at this stage, with the Office for National Statistics estimating that England is around 100,000 infections a day, and the new variant putting pressure on the NHS and the test-and-trace system, pursuing this strategy no longer seems feasible. The immediate priority should be surviving the next few months without the NHS collapsing, and planning for a robust response to eliminate Covid in the spring and summer.

Vaccinating as many people as quickly as possible will be key to this. The UK has decided to vaccinate more people with one dose rather than fewer people with two. This is an ethical and political judgment rather than a scientific one; waiting for follow-up doses to be delivered carries huge costs.

But vaccinating everyone will take time, which is why a national lockdown was necessary. Schools will be closed until mid-February, except for the most vulnerable children and those of essential workers. This will reduce community transmission and allow scientists to gather new evidence about the variant.

As always, mass testing and supported isolation are central to controlling the virus. Both during the lockdown and after these new restrictions are lifted, we should be testing people rapidly to identify those who are carriers, and ensuring those who must isolate have the resources – both financial and practical – to spend 10 days alone. That isolation is an act of goodwill is something the government has repeatedly overlooked during this pandemic, and those who are isolating need to be compensated for doing so.

The government has spent many months and billions of pounds on its testing-and-tracing strategy. So it’s surprising that, despite these efforts, its approach to visitors arriving from overseas is still so lax.

Preventing the import of Covid-19 cases and variants requires robust testing and quarantine procedures at our borders. Yet people are allowed in to the UK without a negative Covid test result, and pictures of crowding at airports – in contrast to the carefully planned approach of countries such as South Korea – do little to instil confidence in the safety of this approach.

Finally, and most importantly, we need to follow these new restrictions, continue to distance from each and avoid crowded spaces and public transport, wear face coverings, and do our best to avoid getting infected and passing the virus on.

We must deprive it of any opportunities to survive and infect others. In the spring, longer days and mass vaccinations will give us another chance to eliminate Covid and prepare for the coming winter. The UK’s health and economy depends upon it.