Covid: What the data which led Boris Johnson to announce the easing of coronavirus restrictions shows

The data on unlocking looks good. But terms and conditions apply.

Monday's Covid-19 press conference was a bit of a formality as these things go.

We will be opening up on May 17, Prime Minister Boris Johnson confirmed and all things being equal, we’re on track to fully unlock on June 21.

But behind the announcement was a lot of hard work by three teams of epidemiologists who have been analysing reams of Covid-19-related data for weeks.

It’s their work that has given the prime minister confidence to take this “single biggest step”.

Previous estimates from February warned of the possibility of a summer wave of infections similar to the peak we have just endured.

• Covid: Easing of lockdown will cause resurgence but deaths projected to be lower due to vaccine uptake

• Covid: One dose of AstraZeneca jab reduces chance of death by 80% while two doses of Pfizer cut it by 97%, PHE says

• Boris Johnson announces big changes to social distancing, travel and hospitality rules from May 17

But the latest projections are much more optimistic.

The prospect of a winter surge in coronavirus cases has disappeared, while tens of thousands could still end up in hospital between now and this time next year, deaths from Covid could be as low as 9,000 in total.

Every one tragic, but given a bad flu year like 2017-18 can kill more than 20,000, nothing that the NHS or wider society can’t handle.

The reason for the far more cheerful forecasts are due to the success of the vaccine roll-out and the fact the jab is preventing the virus from spreading from one person to the next.

Add that to the fact we’ve driven cases down to a low level, and we’re in a good position to start opening up.

The modelling efforts from the three teams of experts from the University of Warwick, Imperial College London and London School of Hygiene and Tropical Medicine are all in pretty good agreement with each other.  

But all of them admit their calculations involve a fair bit of guess work. 

None of them knows just how the virus will behave once we start mixing again.

The B.1.1.7 or “Kent” variant has never really had an opportunity to spread in the absence of lockdown.

For that reason, the fairly wide range in their predictions for, say, total deaths in the next year; varying from around 5,000 to more than 24,000.

They’ve also struggled to predict how we’ll behave.

Will people stick to the “rule of six” for indoor mixing?

Will those of us working from home, suddenly pour back onto public transport?  

And the forecasts also assume there’s no major issues with new variants of Covid or a major hiccup in the vaccination roll-out — either one of which could still derail the roadmap.

Listen to Coronavirus: What You Need To Know, the Covid-19 podcast from ITV News