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Pfizer vaccine gives immunity seven days after second dose, says advisory body


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The Pfizer Covid vaccination today approved for delivery in the UK confers immunity seven days after the second dose is administered, an advisory body has said.

The Commission on Human Medicine (CHM), a DHSC-sponsored non-departmental advisory public body, said this would guarantee the ‘best immunity’ from the vaccine, although ‘partial immunity’ occurs after the first dose.

Speaking in a press briefing today, CHM Expert Working Groups member Professor Sir Munir Pirmohamed said: ‘The vaccine requires two doses 21 days apart and from the data that has been presented to us, people will be immune seven days after the second dose. 

‘Partial immunity does occur after the first dose and we can see some protection occurring after day 12 after the first dose, but best immunity is seven days after the second dose.’

GPs are set to start Covid vaccines by mid-December now that the MHRA has given approval for the delivery of the Pfizer vaccine candidate. 

The Oxford/AstraZeneca vaccine candidate, which is yet to be approved, must also be delivered in two doses.

A new Covid-19 chapter of the Green Book published last week said that Pfizer vaccine doses should be administered a ‘minimum’ of 21 days apart and Oxford/AstraZeneca doses a ‘minimum’ of 28 days apart.

The guidance said: ‘For operational purposes, scheduling the second dose of Covid-19 vaccine from 28 days is recommended (although this would not preclude scheduling Pfizer BioNTech Covid-19 vaccine from 21 days where rapid protection is required). 

‘Using a consistent interval for all two-dose vaccines simplifies the messaging to the public and arrangements within clinic settings where alternative vaccines may be supplied at short notice.’

It added that if a second dose of the Pfizer vaccine is given less than 19 days after the first or a second Oxford/AstraZeneca jab less than 21 days after the first, the dose should be ‘discounted’.

A third dose should be given ‘at least’ 21 or 28 days respectively after the dose given too early, it said.

However, if a longer gap is left between doses, the second dose should still be given and the course ‘does not need to be restarted’, the guidance added.

New PHE guidance also said that different types of Covid vaccines can be used interchangeably if giving two doses of the same version is not possible.

Ahead of approval from the medicines regulator, NHS England published the enhanced service specifications, which said vaccinations by GPs will begin at least ten days after NHS England gives the green light.