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Both Covid vaccines likely to be ‘more effective’ at 12-week intervals, say Government experts

Both Covid vaccines likely to be ‘more effective’ at 12-week intervals, say Government experts

The Oxford Covid vaccine is more effective when the second dose is delayed, according to the UK medicines regulator, with the Government’s expert vaccine committee adding that this is likely to also be the case for the Pfizer vaccine.

Regulatory documents filed by the Medicines and Healthcare products Regulatory Agency (MHRA) said there was ‘more certainty’ of the efficacy of Oxford/AstraZeneca Covid-19 vaccine if the second dose is delayed by eight to 12 weeks after the first.

And documents published by the Joint Committee on Vaccination and Immunisation (JCVI) this afternoon added that there was ‘no strong reason’ to believe the Pfizer/BioNTech vaccine would be any different.

The MHRA has authorised the Oxford/Astra Zeneca vaccine to be given as two doses, separated by four to 12 weeks, and the Pfizer one at two doses between three to 12 weeks.

However, in regulatory documents it has drawn up for healthcare professionals the MHRA said its analysis revealed ‘increased immunogenicity was associated with a longer dose interval’.

It said that giving the second dose eight to 12 weeks after the first provided a more certain immune response.

Oxford University, which developed the vaccine, has also noted the MHRA’s finding about longer intervals between doses ‘may translate into better protection’.

It comes after the UK’s four chief medical officers changed their advice about prolonging the interval between the two doses of the Pfizer/BioNTech vaccine.

GPs are now recommended to delay the second dose by up to 12 weeks – when initially they had been told to give it after three weeks.

The MHRA’s regulatory documents on the Oxford/AstraZeneca Covid-19 vaccine, published this week, said: ‘Exploratory analyses showed that increased immunogenicity was associated with a longer dose interval.

‘Efficacy is currently demonstrated with more certainty for dose intervals from 8 to 12 weeks. Data for intervals longer than 12 weeks are limited.’

Information published by Oxford University in an FAQ said: ‘Our interim results show that the vaccine works well, after the second dose, with an interval of between four and twelve weeks as licensed by MHRA. The MHRA have reviewed the data and believe that the protection is most robust when the booster dose is delivered between four and twelve weeks.

‘The data suggest that a longer interval between doses may increase the effectiveness of the vaccine after the second dose. However more data from the trials will provide greater certainty about this effect.’

It later added: ‘The MHRA label shows that the immune response is stronger with longer intervals between the two doses, and this may translate into better protection.’

Meanwhile, the JCVI report on the new dose regimen said: ‘With most vaccines an extended interval between the prime and booster doses leads to a better immune response to the booster dose. There is evidence that a longer interval between the first and second doses promotes a stronger immune response with the AstraZeneca vaccine.

‘There is currently no strong evidence to expect that the immune response from the Pfizer-BioNTech and AstraZeneca vaccines differ substantially from each other.’


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Please note, only GPs are permitted to add comments to articles

Douglas Callow 6 January, 2021 4:26 pm

conveniently good news for HMG

Patrufini Duffy 6 January, 2021 4:57 pm

Dangerously manipulative and very secret forces of you.

Vinci Ho 6 January, 2021 5:45 pm

(1) OK The argument here is ,longer delay actually is beneficial for Astra-Zeneca Covid vaccine. The corresponding information is available. But what did Pfizer say about their mRNA vaccine , the first of this kind manufactured? They already covered their backside by announcing that they do not support this presumption of the longer the gap ( > 21 days ) , the better . Should any medico-legal challenge arises in the future (in patients catching Covid plus or minus serious/fatal outcomes at the time between 21 days and 12 weeks after first dose of the Pfizer vaccine ), Pfizer will be happy to say ,’ I told you so’!
(2) The politically correct argument of leaving a longer gap so that more people will be vaccinated with first doses , again , appears to be sustainable in the case of Astra-Zeneca vaccine but rather absurd for the Pfizer vaccine . The caveat is potentially having more partially protected patients waiting longer for the Pfizer second ones instead of the original number of so many 95% protected after 21 days in line with the trial results. Of course , everyone is guessing here but the fundamental presumption is the two vaccines behave the same for immunogenicity. And please do not give me ‘ the experts said so ‘ !
(3) The bottom line is , as I could witness so far , the ridiculously unpredictable dates of delivery for all the vaccines to GP sites under the jurisdiction of NHS England/Improvement . The question is why ? Is that really the best NHSE/I can do ?
I would argue if the deliveries are as prompt ,consistent and frequent enough , we would have no problem completing good number of Pfizer ones in recommended two-dose regime , as well as giving many first dose Astra-Zeneca ones away . Bear in mind the both companies said supply was not a problem , yes or no ???

The fact that you two are ‘twins’ does not be necessarily mean you are more or less the same person. Common sense ? But who am I to say that ? Only a layman GP . 😎😈

Iain Chalmers 6 January, 2021 7:48 pm

But then there is a published converse opinion regarding the South African variant and single dose with delayed second to 12/52???

Dave Kew 6 January, 2021 10:03 pm


Patrufini Duffy 6 January, 2021 11:26 pm

Give half the vial, use the same needle, inject the artery, dilute with cordial, immunise celebrities first…just scattergun, made up hypotheses – it’s like the British don’t actually want to win this war. Other nations do. Don’t try and outsmart nature with graphs and lies, it’ll make you look very stupid very very soon.