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The vaccine developed by the University of Oxford and AstraZeneca achieved a 90% degree of effectiveness during clinical trials due to a happy event: a dosage error in some of the participants, reports The Guardian.
Researchers said Monday that the Oxford vaccine was 70% effective overall, but could be 90% effective when given at half the initial dose, followed by a full dose a month later.
“The reason I took a half dose is a happy coincidence,” said Mene Pangalos, AstraZeneca executive vice president of research and development.
When university researchers distributed the vaccine in late April, at the beginning of the partnership between Oxford and AstraZeneca, they found that the expected side effects, such as fatigue, headaches or arm aches, were milder than expected.
“So we went back and checked and found that they had halved the dose of the vaccine,” Pangalos said.
Instead of resuming the study from the beginning, the researchers decided to continue with half the dose and give the full booster dose on the scheduled date.
About 3,000 people received half the dose and then a full dose four weeks later, and the data shows that 90% of the participants were protected from COVID-19 infection. In the largest group, with two full doses, also four weeks apart, the effectiveness was 62%.
Scientists say they cannot yet explain why half the dose provides better protection, but that this can better boost the immune system.
“Giving a small amount of vaccine at the beginning, followed by a larger amount, may be a better way to get the immune system into action, providing the strongest and most effective immune response,” says the teacher. Sarah Gilbert of the University of Oxford, who led the research.
“What we do not know at this time is whether this difference is related to the quality or quantity of the immune response. And we will see that in the coming weeks,” said Professor Andrew Pollard, director of the Oxford Vaccine Group.
The vaccine must be approved by the Medicines and Medical Devices Regulatory Agency, but could be available in the coming weeks if approved.
Editing: Monica Bonea
