It's estimated the world faces as many as 4,000 COVID-19 variants and its prompting a race to improve vaccines, according to researchers in Britain on Thursday.
The announcement comes as the UK has launched a world-first trial that has begun to explore the mixing different vaccine doses.
Thousands of variants have been documented as the virus mutates, including the so-called British, South African and Brazilian variants which appear to spread more swiftly than others.
In an effort to keep ahead of these mutations this trial aims to assess the immune responses generated if vaccine doses from Pfizer and AstraZeneca are combined in a two-shot schedule.
Matthew Snape, an Oxford vaccinologist is leading the trial.
“There's plenty of precedence for this, for these kind of mixed schedules, in other disease areas, such as Ebola and other licensed vaccines, even against HPV and hepatitis B as well.”
The trial will examine the immune responses of an initial dose of Pfizer vaccine followed by a booster of AstraZeneca's, as well as vice versa, with intervals of 4 and 12 weeks.
The team behind the trial are hopeful initial data on immune responses will start to be available from around June.