Britain prefers mix-and-match vaccinations, compounding specialists

Representatives from Public Health England and AstraZeneca did not respond to requests for comment.

Vaccines from both Pfizer and AstraZeneca introduce a protein called spike into the body, which, although not infectious, can teach immune cells to recognize and fight the real coronavirus.

But vaccines provide their immune lessons through different immune systems, and do not contain equivalent ingredients. When Pfizer’s vaccine messenger RNA Or mRNA relies on so-called molecules, which are packed in viscous bubbles, while shots of AstraZeneca are formed around the virus shell that delivers mRNA’s cousin DNA.

Both vaccines are intended to be rolled out in two-regime regiments, delivered at intervals of three or four weeks. While the first shot of each vaccine is thought to be somewhat effective in preventing Covid-1, it is the second dose – as a type of immune molecular review session – that captures the protective process.

While it is possible that switching from one vaccine to another allows the body to enter the school to recognize coronavirus, it is still a scientific gamble. With different components of each vaccine, it is possible that people will not benefit much from the second shot. Mixing and matching can also make it difficult to collect clear data on vaccine safety.

Without evidence to support it, the hybrid vaccination approach seems “premature”, said Saad Omar, a vaccine expert at Yale University. However, it is not without precedent: health officials such as the CDC have previously said that if it is impossible to give a dose of the vaccine from the same manufacturer, “providers should administer the vaccine available to them” so that the injection schedule is complete.

In a controversial move, the British government decided this week to extend its vaccine rollout, delivering the first dose to as many people as possible – a move that could delay a second shot by up to 12 weeks.

Rapid deployment gives more people partial protection against the virus in the short term. But some experts, including Dr Moore, worry that this could also be prudent and endanger vulnerable populations.