Public Health England (PHE) has said it does not recommend mixing COVID-19 vaccines from different suppliers.
The warning comes as distribution of the Oxford/AstraZeneca vaccine is due to start in the UK next week, the second roll-out following the launch of the Pfizer/BioNTech vaccine in December, with both requiring two doses.
On New Year’s Eve, the UK government issued guidance to NHS medics saying that if a person who has received their first jab goes back for their second but the same type is not available, or the first vaccine type is unknown, then it is “reasonable” to offer a dose of another vaccine.
“This option is preferred if the individual is likely to be at immediate high risk or is considered unlikely to attend again,” the guidance adds.
After questions were raised about the risks, Dr Mary Ramsay, head of immunisations at PHE, told Sky News that mixing is not recommended and should only happen on “rare occasions”.
“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 said.
“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.”