In a surprising move, the British government has said in its Covid-19 vaccine recommendations that it is reasonable for people to mix and match different Covid-19 vaccines.
The UK has approved two Covid-19 vaccines to combat the pandemic -- AstraZeneca and Pfizer. Both vaccines require people to get two shots of the vaccine several weeks apart.
Although there is no evidence that taking two different Covid-19 vaccine shots works, the British government suggested people may mix and match their shots in its guidelines on the Covid-19 vaccine updated on New Year’s Eve, according to Business Insider.
If "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 UK's new advice for providers reads.
However, the British government noted in its guidelines that "there is no evidence on the interchangeability of the Covid-19 vaccines."
Experts said mixing two vaccines is a risky, untested strategy.
"We're kind of in this wild west," Dr Phyllis Tien, an infectious disease physician at the University of California, San Francisco, told the New York Times. "None of this is being data driven right now."
The UK launched the mix and match trial to find out if mixing different vaccines together could provide people with more robust protection from infection.
"The idea is that you can maximize the strength of that immune response to protect people," Kate Bingham, chair of the UK's vaccine task force, said during a recent briefing.
Pfizer's vaccine is a new kind of messenger RNA vaccine, while AstraZeneca is using viral vector technology.
"Antibodies block the uptake of viruses into cells, and the cellular T-cells identify those cells that have been infected and take them out," Bingham said. "You ideally want to have both."
However, in the US, the Centres for Disease Control and Prevention (CDC) said that the authorized Covid-19 vaccines “are not interchangeable.”
According to the CDC, as 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.
But John Moore, a vaccine expert at Cornell University, wants more evidence that the strategy can really work before it is recommended.
Moore told the New York Times that officials "seem to have abandoned science completely now and are just trying to guess their way out of a mess."
The UK has been seeing a surge in coronavirus infections recently as a new fast-spreading variant was discovered in the country.
However, the new variant, called B.1.1.7, is not more deadly, and experts expect vaccines will be successful at fighting it, too.
The country is now pushing to get as many people vaccinated as possible.
The UK has reported 2,542,065 Covid-19 cases while 74,125 people succumbed to death from the deadly virus till Saturday afternoon, according to Worldometers.