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Mixing vaccines ‘could lead to better immune responses’

booster doses

The health secretary has said he is ‘encouraged’ by the Covid vaccine ‘mix and match’ trial, which shows that using different vaccines for first and second jabs could ‘possibly’ lead to better immune responses.

In his first statement to Parliament as health secretary yesterday, Sajid Javid said that using a different vaccine for second dose will allow for more ‘flexibility’ in the vaccination programme.

Pulse reported in April that researchers at the University of Oxford were hoping to publish results in May or June, and the team has now issued a preprint on the trials. 

The preprint of the study also showed that mixing vaccines was especially beneficial for those who had been given a first dose of the AstraZeneca vaccine. 

Previous reports suggested that mixing the Astrazeneca and Pfizer vaccines is more likely to lead to mild and moderate side effects. 

The Government is looking to schedule a booster programme in the autumn, and it is expected that this study, when finalised, will be crucial in determining the structure of the programme. 

Speaking in the Commons, Mr Javid said: ‘I’m encouraged by new data just today from Oxford University’s “mix and match” trial, which show that a mixed schedule of jabs — such as getting the AstraZeneca jab first then Pfizer second – could give our booster vaccination programme more flexibility – and possibly even some better immune responses.

The University of Oxford extended the study in April to include the Moderna and Novavax vaccines, in addition to Pfizer and AstraZeneca.

The Government commissioned the study, which had originally looked at using the AZ and Pfizer vaccines interchangeably through four different combinations, in February.

The study is comparing immune system responses between the first and second vaccine doses and any adverse reactions to the ‘gold-standard’ responses reported in previous clinical trials of each vaccine.

Dr Peter English,  a GP and immediate past chair of the BMA Public Health Medicine Committee, said:One of the facts that is familiar to vaccinologists, but perhaps not so widely understood, is that heterologous boosting – priming with one vaccine, and then using a different vaccine for the booster dose – is commonly more effective than homologous boosting, using the same vaccine.4 5

‘This is another paper confirming that, at least with a four-week interval… mixing Pfizer-BioNTech and Oxford-AstraZeneca vaccines produces at least as strong a response as do heterologous schedules.’

Prof Paul Hunter, professor in medicine at UEA, said: The big question at present is whether or not we will be being offered booster vaccines in the Autumn. With the evidence available from this and other sources, I suspect that will be likely for those most at risk from the virus, either due to age or being clinically vulnerable. 

‘From this study, people who have had a first course of AstraZeneca should probably be offered the Pfizer vaccine (or possibly Moderna or Novavax dependent on the future trial data from this study) in the autumn rather than a repeat AstraZeneca. People who had a Pfizer first course may not need an autumn booster but if they do then it probably does not matter much which vaccine they are offered.’


terry sullivan 29 June, 2021 10:57 am

could or will?

i will avoid mrna

Patrufini Duffy 29 June, 2021 1:48 pm

I am going to mix sertraline with nitrofurantoin, propranolol and azithromycin soon. There will be the option of a naproxen coating.

Patrufini Duffy 29 June, 2021 3:50 pm

Mixing complacency, privilege and ego is a bad option. Like football fans, generation-ME and beer, equally wasteful. But who cares, pandemic is over.

terry sullivan 30 June, 2021 7:13 pm

never was a pandemic