One dose of Oxford/AstraZeneca’s COVID-19 vaccine is around 70% effective after 21 days and before the second dose is given, a British doctor involved in the approval of the vaccine said on Wednesday (December 30).
“The data shared with us, and I’m not sure is entirely in the public domain, calculated the vaccine efficacy between day 22 of dose one, to the time of dose two being given, and the figure is around 70%,” said Wei Shen Lim, chair for COVID-19 immunisation of the Joint Committee on Vaccination and Immunisation, during a briefing in London.
Britain on Wednesday (December 30) became the first country in the world to approve a coronavirus vaccine developed by AstraZeneca and Oxford University as it battles a winter surge driven by a new, highly contagious variant of the virus.
The British government said it had accepted a recommendation from the Medicines and Healthcare products Regulatory Agency (MHRA) to grant emergency authorisation.
MHRA Chief Executive Dr. June Raine said at the briefing in London that the vaccine had been approved for adults, with two standard doses four to 12 weeks apart.
She said the MHRA has taken independent laboratory testing to assure that “every single batch meets the same standards of safety and quality.”
The first batch of the COVID-19 vaccine was released on Tuesday (December 29) night, she added.
Britain is the first country in the world to approve the coronavirus vaccine developed by Oxford University and AstraZeneca, hoping that rapid action would help it stem a surge of infections driven by a highly contagious variant of the virus.
Boris Johnson’s government, which has already ordered 100 million doses of the vaccine, has jumped ahead of other Western countries with its vaccination programme.
The AstraZeneca/Oxford shot, unlikely to be approved for some time by EU or U.S. regulators, will start being administered on Monday, beginning with those most at risk from COVID-19.
Uncertainty has swirled over the most effective dosing pattern for the AstraZeneca/Oxford vaccine since it released data last month showing a 90% success rate for a half-dose followed by a full dose, but only 62% – still usually more than enough for regulators – for two full doses.
The MHRA said that the results for the half-dose regimen had not been borne out by analysis. Instead, it approved the regimen of two full doses.
An official involved in the MHRA decision said that the vaccine’s effectiveness had risen when the doses were given three months apart.
“Effectiveness was high, up to 80%, when there was a three-month interval between first and second doses, which is the reason for our recommendation,” Munir Pirmohamed, Chair of the Commission on Human medicines expert Working Group on COVID-19 vaccines, told reporters.
While the approval by the MHRA is a vindication for a shot seen as essential for mass immunisations, it does not eliminate questions about trial data that make it unlikely to be approved so rapidly in the European Union or the United States.