AstraZeneca vaccine works better if doses given further apart

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The scientists who developed the AstraZeneca/Oxford vaccine have said that it is more effective if there is an interval of at least 12 weeks between the first and second doses rather than six.

"A 3-month dose interval might have advantages over a programme with a short dose interval for roll-out of a pandemic vaccine to protect the largest number of individuals in the population as early as possible when supplies are scarce, while also improving protection after receiving a second dose," the vaccine's lead developer, Andrew Pollard of Oxford University, wrote in an article published in The Lancet medical journal on Friday.

The results of recent clinical trials, involving more than 17,000 people in Britain, South Africa and Brazil, support the British government's strategy of allowing a longer interval between the first and second doses of the AstraZeneca vaccine.

The vaccine showed an efficacy rate of 81% with an interval of at least 12 weeks between the first and second doses - up from 55% with a 6-week interval between the two doses.

The report also said that a single standard dose of the Oxford/AstraZeneca vaccine is 76% effective from day 22 to day 90 after the jab - meaning protection was not reduced in the three months between the first and second dose.

Germany's Standing Committee on Vaccination (Stiko) has so far recommended that the second dose of AstraZeneca's jab be administered 9 to 12 weeks after the first. Some other vaccines, such as for flu, Ebola and malaria, also provide greater protection and stronger immune responses after a longer interval between doses.

However, the researchers are urging people to have two doses of the vaccine since is not yet clear how long protection with a single dose of a COVID-19 jab may last.

More on this subject: Coronavirus

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