England's health agency has warned against mixing vaccines from different suppliers after a US newspaper reported an update to Public Health England's Covid handbook that would allow for a "mix-and-match" vaccine roll out.
Later, the agency's coronavirus 'green book' adds: “There is no evidence on the interchangeability of the Covid-19 vaccines although studies are under way.”
Commenting on reports on mixing vaccines, Dr Mary Ramsay, Head of Immunisations at PHE, said: “We do not recommend mixing the Covid-19 vaccines – if your first dose is the Pfizer vaccine you should not be given the AstraZeneca vaccine for your second dose and vice versa.”
She added: "There may be extremely rare occasions where the same vaccine is not available, or where it is not known what vaccine the patient received.
"Every effort should be made to give them the same vaccine, but where this is not possible, it is better to give a second dose of another vaccine than not at all."
Dr Ramsay was forced to defend the UK's vaccine regimen after an article in the New York Times report accused Britain of deploying a "mix-and-match" approach to the vaccine roll out.
The report quoted virologist Prof John Moore from Cornell University in the US who accused the UK of having "abandoned science completely now and are just trying to guess their way out of a mess”.
Prof Anthony Harnden, the deputy chair of the Joint Committee on Vaccination and Immunisation, told BBC Radio 4’s Today programme: “Our current advice is that you use the same vaccine for both doses. However, we have studies that are ongoing at the moment to look at mixing vaccines and when we see the data for those and are secure about the data for those, then we may be recommending mixed dose strategy.”
He also insisted delaying the second anti-Covid dose was the right strategy, stating: “I don’t think this is a supply issue, as much as trying to get as many vaccines into as many people as possible.
“And, I accept that it may cause mistrust if we don’t communicate this properly.”