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Delayed Pfizer vaccine dose gives 3.5 times more immunity, study shows

Published on 14/05/21 at 10:11am
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The Pfizer-BioNTech COVID-19 vaccine is around three and a half times more effective when dosed 12 weeks apart, a Birmingham University study has shown.

The jab, which requires two injections to be fully effective, was originally recommended by Pfizer and BioNTech to be given twice three weeks apart. However, the UK government chose to extend the gap to 12 weeks in order to vaccinate as many people as possible with an initial dose first.

The study, which took blood samples from 175 over-80s after their first and second shots, found that those who received their booster dose 12 weeks after their first jab had three and a half times more antibodies than those who were vaccinated just three weeks apart.

It was also found, however, that peak T-cell count was higher in those who had the doses just three weeks apart, which could be a marker for longer term immunity in that group.

This is the first study into the effectiveness of dosing the Pfizer-BioNTech vaccine 12 weeks apart, appearing to justify the UK government’s risky strategy. The Oxford-AstraZeneca jab, which has also been used in the UK since the turn of the year, has already proven to be stronger when administered 12 weeks apart rather than 3, as reported in an Oxford University study in February. 

Helen Parry, Co-Author of the Pfizer vaccine study, told Reuters: ”Our study demonstrates that peak antibody responses after the second Pfizer vaccine are markedly enhanced in older people when this is delayed to 12 weeks.”

The study, which was released today in pre-print form, is yet to be peer-reviewed.

Gayatri Amirthalingam, Consultant Epidemiologist at Public Health England, said that, ”The approach taken in the UK for delaying that second dose has really paid off.”

The UK’s 12-week strategy has allowed more people – 35,906,671 – to be vaccinated with a first dose, although it does mean only around half of these – 18,890,969 people – have been given a second dose so far. This equates to roughly 68% and 36% of the total UK adult population respectively.

Jack Goddard

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