People who have received the AstraZeneca jab may not need a booster because they should be protected against Covid for longer, the firm’s chief executive has said.
Pascal Soriot suggested that the Oxford jab may elicit a stronger T-cell response than the vaccines produced by US companies Pfizer and Moderna.
The firm is waiting for further data which may prove that millions of older Britons given the AZ jab do not need another dose, he said.
Ministers are drawing up plans to offer booster shots to 32 million people amid evidence that the protection offered by Covid vaccines gradually wanes.
"We hope that the Oxford-AstraZeneca will provide longer-term protection," Mr Soriot told the Daily Mail.
"The science so far suggests that our vaccine provides a strong T-cell response, which I hope means its effects will last longer. So it looks good, but we don’t yet know for sure whether you will need a booster. Time will tell."
Scientists believe T-cells, a type of white blood cell, may provide longer-lasting immunity to Covid than antibodies. In April, a Birmingham University study found that the AstraZeneca jab appeared elicit a stronger T-cell response than either Pfizer or Moderna.
Meanwhile, data collected by Johnson & Johnson, whose vaccine is based on the same technology as the AZ jab, showed it "provides years of protection", Mr Soriot said.
Pfizer has admitted that the effectiveness of its MRNA vaccine steadily declines over time, dropping to about 84 per cent for vaccinated people about four to six months after getting their second dose.
Conclusive data comparing the jabs is expected by October or November. By that time, however, the Government’s booster programme is expected be up and running.
Third doses are set to be offered to 32 million Britons, with an average of almost 2.5million third doses a week, starting in the first week of September.
All adults aged 50 and over, as well as the immuno-suppressed, will be offered the booster jabs. The campaign could start as soon as September 6, which would see the rollout completed by early December if it goes to plan.