British health officials will now allow people to mix COVID-19 vaccines as the pandemic rages on — but experts warn it could be risky.
The tweak in vaccine advice, which comes as the country grapples with a new, highly contagious mutation of the virus, marks a surprising departure from previous guidance — and a starkly different approach to the vaccine rollout in the US, the New York Times reported.
The UK protocol now states that a person can receive their follow-up COVID-19 jab with a different vaccine candidate to their first dose, if necessary.
Britain has approved two vaccines for the deadly bug, developed by AstraZeneca and Pfizer.
“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,” the updated guidance states.
However, the protocol does reiterate that receiving a second dose of the same vaccination is preferable, noting that a different inoculation should only be used if the patient is 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,” it explained.
But the new advice has still raised eyebrows in the scientific community.
“There are no data on this whatsoever,” Cornell University vaccine expert John Moore told the Times, adding that the UK officials “seem to have abandoned science completely and are just trying to guess their way out of a mess.”
The update also stands in contrast to the guidelines established by the US Centers for Disease Control and Prevention, which explicitly states that the vaccines “are not interchangeable.”
“Either of the currently authorized mRNA COVID-19 vaccines can be used when indicated,” the CDC wrote, noting that the Advisory Committee on Immunization Practices “does not state a product preference.”
“However, these mRNA COVID-19 vaccines are not interchangeable with each other or with other COVID-19 vaccine products,” the agency said. “The safety and efficacy of a mixed-product series have not been evaluated.”
The CDC does go on to say that if doses of different vaccines are “inadvertently” given, then no additional doses of either vaccine should be administered.
When contacted by The Post, the CDC declined to comment on the UK’s updated guidance and whether it would reassess its own guidance in light of the new advice.
The US has signed off on two coronavirus vaccines, developed by Pfizer and Moderna.
The UK, which has surpassed 2.5 million confirmed COVID-19 cases, is battling a surge in infections as a more contagious variant sweeps across the country — prompting at least 17 countries to announce British travel bans.