Officials have defended England’s vaccine regimen after details of a contingency plan to potentially mix the two approved jabs in small numbers of cases emerged.
Public Health England’s Covid “green book” recommends that “it is reasonable to offer one dose of the locally available product to complete the schedule” if the same vaccine used for the first dose is not available. But it adds: “There is no evidence on the interchangeability of the Covid-19 vaccines although studies are under way.”
Criticism erupted following the publication of a New York Times report which quoted virologist Prof John Moore, from Cornell University in the US, who said “there are no data on this idea whatsoever” and that British officials “seem to have abandoned science completely now and are just trying to guess their way out of a mess”.
The American infectious disease expert Dr Anthony Fauci said on Friday he did he not agree with the UK’s approach of delaying the second dose of the Pfizer/BioNTech vaccine. He told CNN that the US would not be following in the UK’s footsteps and would follow Pfizer and BioNTech’s guidance to administer the second dose of its vaccine three weeks after the first.
The head of immunisations at Public Health England, Dr Mary Ramsey, said mixing was not recommended and would only happen on extremely rare occasions.
She said: “If your first dose is the Pfizer vaccine you should not be given the AstraZeneca vaccine for your second dose and vice versa. 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.”
On BBC Radio 4’s Today programme, Prof Anthony Harnden, the deputy chair of the Joint Committee on Vaccination and Immunisation, said: “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 and frontloading the first dose rollout was the correct 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.”
The “green book” states: “If the course is interrupted or delayed, it should be resumed using the same vaccine but the first dose should not be repeated. There is no evidence on the interchangeability of the Covid-19 vaccines although studies are under way. Therefore, every effort should be made to determine which vaccine the individual received and to complete with the same vaccine.
“For individuals who started the schedule and who attend for vaccination at a site where the same vaccine is not available, or if the first product received is unknown, it is reasonable to offer one dose of the locally available product to complete the schedule. This option is preferred if the individual is likely to be at immediate high risk or is considered unlikely to attend again.
“In these circumstances, as both the vaccines are based on the spike protein, it is likely the second dose will help to boost the response to the first dose. For this reason, until additional information becomes available, further doses would not then be required.”
The guidance, published on Thursday, contradicts guidelines in the US, the New York Times reported. According to the Centers for Disease Control and Prevention, the authorised Covid vaccines “are not interchangeable”, and “the safety and efficacy of a mixed-product series have not been evaluated. Both doses of the series should be completed with the same product.”
Pfizer spokesman Steven Danehy told the paper: “While decisions on alternative dosing regimens reside with health authorities, Pfizer believes it is critical health authorities conduct surveillance efforts on any alternative schedules implemented and to ensure each recipient is afforded the maximum possible protection, which means immunisation with two doses of the vaccine.”
The UK is preparing to send out the new Oxford University and AstraZeneca vaccine with 530,000 doses available for rollout from Monday, amid reports that 2m doses are due to be supplied each week by the middle of January.