It is not a "safe bet" to rely on immunity to Covid-19 as a strategy for coping with the pandemic, one expert has warned, adding that herd immunity strategies were "probably never going to work."

Speaking Monday on CNBC's "Squawk Box Europe," Danny Altmann, professor of immunology at Imperial College London, said that in towns and cities where there had been coronavirus infections, only 10% to 15% of the population was likely to be immune.