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The vaccine developed by the University of Oxford and AstraZeneca reached 90% effectiveness during clinical trials following an error, as a result of which some volunteers received only half a dose of the vaccine, writes The Guardian.
AstraZeneca announced Monday that its vaccine is 70% effective, but the percentage can rise to around 90% when only half the dose is given, followed by a full dose after a month.
“The reason the half dose was given was a happy event,” said Mene Pangalos, vice president of research and development for AstraZeneca.
When the researchers distributed the vaccine in late April, at the beginning of the partnership between the University of Oxford and AstraZeneca, they found that the expected side effects, such as fatigue, headaches, or arm aches, were milder than expected.
“We went back, checked, and found that they had halved the dose of the vaccine,” Pangalos explained.
Rather than start over, the researchers decided to continue testing and administer the second full dose on the scheduled date.
About 3,000 people received half the dose and then a full dose four weeks later. The data showed that 90% of these people were protected by Covid-19. In the largest group, where volunteers were given two full doses of the vaccine, also four weeks apart, the effectiveness was only 62%.
Scientists say they still can’t fully explain why half a dose provides better protection, but it can affect the immune system differently.
“By giving a small amount of vaccine at the beginning, followed by a higher dose, it can be more effective in stimulating the immune system and eliciting a stronger immune response,” said Professor Sarah Gilbert of the University of Oxford, who led the research. .
“What we do not know at this time is whether this difference is in the quality or quantity of the immune response. And we will look at this in the coming weeks,” said Professor Andre Pollard, director of the Oxford Vaccine Group.
The vaccine has not yet been approved by regulatory agencies for drugs and medical devices, but it could be available in the coming weeks if approved.
