Covid experts issued “vital” advice to Brits today after rules that sent millions of contacts into isolation finally came to an end.
A member of SAGE warned there could yet be a “large” wave this September as England celebrated new-found freedoms from quarantine.
From today in England, double-jabbed adults and any children who come into contact with a Covid case will no longer have to isolate.
The NHS Covid-19 app - which was already made less sensitive on August 2 - will allow 'pinged' close contacts to skip isolation if they are fully vaccinated.
But crucially, close contacts are still being advised to take a ‘gold standard’ PCR Covid test - even though this is not a legal requirement.
And if that test comes back positive, they must then isolate by law.
Two advisors to the government today warned it will be crucial for Brits to follow that advice to minimise a fresh wave of disease.
Professor Stephen Reicher, from the University of St Andrews, told Sky News the vaccines are "not perfect", adding: "You can still be hospitalised, you can still get infected, you can still infect others.
"So I think it's really important to say to people that having a PCR test is absolutely vital - it should be more than just 'Do it if you want to do it’.”
He added: "I think it would have made sense to ask people to self-isolate until they get the results of that test, but at the very least be cautious."
SAGE member Prof Neil Ferguson told the BBC: “It very much depends on the extent to which people do take that advice and get tested.
“Inevitably lifting some measure like this will slightly reduce the effectiveness of contact tracing - but only slightly, so long as people do take the advice to get tested and if they’re positive, isolate.”
Despite his advice, Prof Ferguson warned there may still be a “large wave” of coronavirus in September or October.
He told BBC Radio 4’s Today programme: “Case numbers have basically plateaued at this time and are really quite high - it’s about 30,000 cases a day.
“That’s a slightly sobering situation to be in coming into September because our contact rates are at about half of normal levels, and in school holidays children don’t have that many contacts.
“And we’ll be reopening schools, people will be going back to offices in September.
“So we still have the potential of quite a large wave of infection in September, October.”
Asked if cases could still hit 100,000 per day, as he predicted earlier in the summer, he said: “I’ve learned my lesson in terms of being over eager making those sorts of predictions.”
But he added: “It’s possible, it’s very hard to make those predictions at the moment.” And he said in the worst case scenario there could still be “well over 1,000 admissions a day” to hospital.
Prof Ferguson said that due to vaccines, “we’re not going to be stopping this wave with lockdown” and deaths are likely to be lower than in the second wave.
"I think overall the population has been really quite cautious coming out of this last lockdown,” he added, with “much lower contact rates” than before the pandemic or even than last summer.
Under the change in the rules today, people who had a second dose at least 14 days earlier no longer have to isolate if they have close contact with a Covid sufferer.
However, they still are advised to “limit” close contact with friends and family, “especially in enclosed spaces”.
They are also advised to limit contact with the extremely vulnerable, wear a face covering in enclosed spaces, and of course take a PCR test.
Close contacts must also still isolate if the contact is a member of their own household.
Prof Reicher today said he was relatively optimistic about the levels of coronavirus cases in England as new rules surrounding isolation come into force on Monday.
Speaking in a personal capacity, he told BBC Radio 4's Today programme: "After the reopening on July 19, many of us thought infections would go up massively to 50,000 or 100,000 a day, perhaps they still will, but they didn't.
"There's never a single cause but one of the major reasons why they didn't was the good sense of the public - people remained cautious, people remained careful, so I have a good amount of faith in the good sense and the caution of the public."
But he added: "The problem is that if you now make it a choice to people as to whether to take a test, and therefore have to self-isolate if you're positive, people aren't going to take that test if they can't afford to be positive.
"So we need to give people more support, so they can self-isolate."
