Rapid Covid tests should not be used as a green light for those who test negative to abandon social distancing, a senior member of the NHS Test and Trace operation has warned.
Lateral flow tests are being deployed to enable students to return home for Christmas and care home residents to have visitors, and Boris Johnson this week suggested that there was “a real possibility” that they will allow events like weddings to go ahead in a more normal way.
But Dr Hopkins, who is chief medical adviser to Test and Trace, said it was vital to “resist” the message that a negative result meant individuals could relax their guard and return to more normal social contacts.
Lateral flow tests, which can give a result within minutes, were useful in swiftly identifying and isolating asymptomatic carriers of Covid-19, she said. But they missed too many cases of infection for a negative test to be regarded as proof that an individual is free of the disease.
“We've been very clear that this test finds people that doesn't we couldn't otherwise find,” Dr Hopkins told BBC Radio 4’s Today.
“We’re also very clear that until we get a much lower prevalence of disease in this in this country that we shouldn't be changing our behaviours.
“Where we're using this test is where people are already doing something. And this gives them an extra piece of information on top. What we're not saying at the moment that we should be releasing everything.”
Dr Hopkins said that NHS Test and Trace was not pushing for the tests to be used to allow people to have more social contact at events like weddings or sports matches.
“We need to resist that until we've got the prevalence in the community at a much lower level,” she said.
“Clearly if we've got the prevalence in the community to … where we were in the summer when there was a very small number of cases around, then that's the thing that makes the greatest impact on reducing transmission of disease. These tests are an add-on.
Dr Hopkins also revealed that NHS Test and Trace is considering asking all contacts of coronavirus carriers to have lateral flow tests as soon as they are identified, rather than waiting to see if they develop symptoms themselves.
She said the move could encourage more people to self-isolate, after research found that as few as 11 per cent of close contacts told to go into quarantine actually do so.
At present, people who test positive for coronavirus are asked to list recent close contacts, who are tracked down and told to stay home and avoid social contact for 14 days.
But Dr Hopkins said that the low level of compliance was forcing officials to consider changing their methods.
“We have to look at new methods of discussing this with people,” she said. “We have to find the cases, because we all know that we are much more likely to change our behaviour if we know we're positive.
“Testing people who are contacts, testing people who are in settings where we know there's lots of cases, will be the most effective way of getting people to isolate.”
Asked whether a move to testing all contacts was under consideration, she replied: “That's definitely something we are evaluating and testing at the moment, to see if it's an effective way forward. We're not there yet, but we will definitely be working hard to see - now that we have these tests - whether that's something that we can do.”