Asked about test-and-trace, the prime minister says a new operation on this scale will have "teething problems", but capacity is increasing.
Collaboration with councils is "integral" to the programme, he adds. It's of "such importance and such value" in fighting Covid, the PM adds.
With vaccines there is an "oasis" but there will be "hard months ahead", with testing "vital", Johnson predicts.
Prof Chris Whitty says it's "pretty obvious" that relaxations over Christmas will come "at a risk". People must behave responsibly before, during and after the holidays, he warns.