Oxford Covid jab falls short of Pfizer and Moderna vaccines for herd immunity - what scientists said

Friday, 22nd January 2021, 3:35 pm
Updated Friday, 22nd January 2021, 3:35 pm
The Oxford jab was found to have an efficacy of 62 per cent (Photo: Getty Images)
The Oxford jab was found to have an efficacy of 62 per cent (Photo: Getty Images)

Scientists are recommending that all health and social care professionals should be vaccinated with the Pfizer or Moderna Covid-19 vaccines as they have proved to be more effective.

Researchers from the University of East Anglia have warned that the Oxford vaccine is ‘less effective’ in controlling the spread of the virus, and would need to be given to more than 90 per cent of the population to drive infection rates down.

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Why is the Oxford jab less effective?

Professor Paul Hunter and colleague Alistair Grant, from the University of East Anglia, have warned that herd immunity cannot be achieved either through natural infection, or by the rollout of the Pfizer and Oxford vaccines.

While vaccines will make a huge difference in stopping people from getting ill and suppressing the spread of infection, Prof Hunter said that they will not completely stop it.

As such, people who refused to have the vaccine will continue to be at risk.

However, the scientists have recommended that health and social care workers should be given either the Pfizer or Moderna jabs, as these have both reported around 95 per cent efficacy in clinical trials.

By administering these jabs, it would more effectively prevent patients and the vulnerable from becoming infected.

The researchers used mathematical modelling to assess how effective the Oxford and Pfizer vaccines would be in bringing the coronavirus reproduction number (R) down.

Initial findings showed that 69 per cent of the population would need to be given the Pfizer jab to bring the R number below 1, whereas this would need to be as high as 93 per cent with the Oxford vaccine.

When taking into account the highly transmissible UK variant, they found that vaccinating the entire UK population with the Oxford jab would only reduce the R value to 1.3.

Prof Grant said the combination of “relatively low headline efficacy and limited effect on asymptomatic infections” means the Oxford vaccine “cannot take us to herd immunity, even if the whole population is immunised”.

He said: “For this reason, we recommend that health and social care workers, and others who have lots of contacts with those vulnerable to infection, should receive one of the mRNA vaccines in preference.“The Oxford vaccine will no doubt be an important control intervention, but unless changes to the dose regime can increase its efficacy, it is unlikely to fully control the virus or take the UK population to herd immunity.”

How effective is the Oxford vaccine?

The Oxford/AstraZeneca jab began its rollout on 4 January after being granted approval by the Medicines and Healthcare products Regulatory Agency (MHRA) following clinical trials.

Trial participants were given different dosing regimens of the vaccine, with some receiving two full doses and some a half dose followed by a full.

The MHRA approved the use of two full doses, which was found to have an efficacy of 62 per cent.

Prior to being granted approval in the UK, the Oxford team reported levels of 90 per cent effectiveness in participants who had been given a half dose followed by a full dose.

However, Professor Munir Pirmohamed, chair of the MHRA, said the 90 per cent efficacy rate did not hold up under analysis and that other factors may have led to this result.

The greatest benefit of the vaccine is that it can be stored at fridge temperature of between 2C and 8C for at least six month, unlike the Pfizer vaccine which requires ultra-low temperatures as cold as -80C.

The UK government has ordered 100 million doses of the Oxford vaccine which would be enough to immunise 50 million people.