But a major hurdle that could slow its rollout in the U.K. after yesterday’s approval is the question of how to best use the vaccine in the real world.
Complicating matters is U.K. regulators’ decision to allow the second dose of the vaccine to be administered up to 12 weeks after the first dose. The Medicines and Healthcare Products Regulatory Agency, the country’s regulatory authority, estimated that the plan would enable the U.K. to double the number of vaccine recipients in the coming months. But the 12-week period is a longer time period than most of the Phase 3 clinical trial participants waited for a second dose.
The three-month gap is a pragmatic solution to the question of how to vaccinate as many people as possible, while vaccine supplies are likely to be scarce for some time and Britain struggles with what appears to be a more contagious variant of the novel coronavirus.
The plan would allow more than 20 million people in the U.K. to receive the vaccine starting Jan. 4 while waiting for production to ramp up to allow wide-scale distribution of the second dose.
While experts agree that the vaccine is safe, as the Guardian observed, determining how to optimize the vaccine’s efficacy is a thornier question.
According to an interim analysis of a Phase 3 trial, the vaccine had an efficacy of 62% in individuals who received two doses of the vaccine at least one month apart. But a smaller group of study participants received the second vaccine dose later than the majority. Some study volunteers were inoculated with the second dose 26 weeks after the first. For the outliers who received the second dose later than the rest, efficacy rose to 70%.
While it is common for a booster to be more effective with a significant time gap, the limited data available regarding the vaccines may leave the U.K. to figure out how to best use the vaccine. The country has already been aggressive in its rollout of vaccines, delivering more vaccine doses per capita than any other country but Israel and Bahrain.
Following the U.K.’s decision to authorize the vaccine will likely lead other nations to follow in its footsteps, putting more demands on AstraZeneca to ramp up production. India, however, began stockpiling the vaccine in April and has 40 million doses waiting.