AstraZeneca might have to run an additional global trial to assess the efficacy of its COVID-19 vaccine, after concerns were raised about the effectiveness of its jab.

Several scientists have raised doubts about the robustness of results released on Monday showing the experimental vaccine was 90 percent effective in a sub-group of trial participants who, by error initially, received a half-dose followed by a full dose.

Soriot said he did not expect the additional trial to delay United Kingdom and European regulatory approvals.

Earlier he had said that the firm would start discussions with the FDA to change the design of its experimental COVID-19 vaccine trial to add the more-effective dosage regime.

Meanwhile on the same day, the British government’s Chief Scientific Adviser Patrick Vallance said that the main point about the AstraZeneca vaccine against COVID-19 was that it worked, when asked about doubts that have been raised about the vaccine.