the evidence behind the government’s Covid-19 vaccine dosing strategy – .

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the evidence behind the government’s Covid-19 vaccine dosing strategy – .


When the UK first suggested a 12-week gap between Covid-19 vaccine doses, it was seen as a gamble.

The decision was taken in December 2020, at the start of the vaccination campaign, with the aim of protecting as many as possible in the face of increasing cases and uncertain supply.

Still, the policy was enacted on somewhat shaky ground – particularly for the Pfizer jab, which had not tested the longer interval in clinical trials.

So far, however, the gamble appears to have been won, with a roaring vaccination schedule, declining death rates and mounting evidence supporting this decision.

But this week – in a bid to speed up the rollout of vaccination in Britain in the face of the delta variant – the government announced that the gap between vaccine doses would be reduced from 12 weeks to eight for all adults, for all vaccines being deployed. across Brittany. This follows a similar move closing the dosing gap for those over 40 taken last month.

So what is actually the optimal time interval between doses of the three vaccines currently in use in the UK – Oxford University / AstraZeneca, Pfizer / BioNTech and Moderna?

Our Global Health team takes a look.

University of Oxford / AstraZeneca

The makers of this jab recommend that the second hit come between eight and 12 weeks after the first.

This is a guideline that the UK has followed, moving from one end of the period to the other depending on the supply situation, the individual’s medical history and the risk of infection.

But it’s increasingly clear that aiming for the lower end of that range provides slightly higher protection at the population level.

According to test data published in The Lancette in January, the AstraZeneca vaccine is 82.4% effective in stopping infection when a second injection is given at least 12 weeks after the first. This figure drops to around 55 percent if the second dose is given within six weeks. This effectively suggests that the larger gap will ultimately prevent more infections in the population.

A more recent prepublication, published in June, looked at the antibody responses of 30 people who received their second injection of AstraZeneca later than expected. He found that those who saw a 45-week gap had a significantly higher antibody response after their second dose.

In reality, however, no one is suggesting that individuals wait this long for more protection, especially when dealing with highly contagious variants.

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