TWO doses of the Pfizer/BioNTech vaccine appears to have greater effectiveness initially against new Covid-19 infections associated with the Delta variant when compared to the Oxford/AstraZeneca jab, but its efficacy also declines faster, preliminary research suggests.

Scientists from Oxford University have said that after four to five months, the level of protection offered by both vaccines is similar, with the AstraZeneca jab maintaining its effectiveness throughout the duration.

ALSO READ:  Oxfordshire hits 50,000 Covid cases since the pandemic began

The findings, which have not yet been peer reviewed, also suggest that those infected with the Delta variant after their second jab had similar peak levels of virus to unvaccinated people.

Based on their work, the researchers said that although jabs did not eliminate chances of getting Covid-19, they did reduce the risk and remained the most effective way to ensure protection against the Delta variant – which has become dominant in the UK.

Sarah Walker, professor of medical statistics and epidemiology at the University of Oxford, said: “We don’t yet know how much transmission can happen from people who get Covid-19 after being vaccinated – for example, they may have high levels of virus for shorter periods of time.

“But the fact that they can have high levels of virus suggests that people who aren’t yet vaccinated may not be as protected from the Delta variant as we hoped.

“This means it is essential for as many people as possible to get vaccinated – both in the UK and worldwide.”

ALSO READ: Barton summer school tackling impact of Covid-19 pandemic

The study, conducted in partnership with the Office of National Statistics (ONS) and the Department for Health and Social Care (DHSC), looked at data between December 2020 and August 2021 from the Covid-19 Infection Survey.

Swab tests from more than 700,000 participants were analysed from before and after May 17 2021, when Delta became the main variant in the UK.

Analysis revealed that for infections with a high viral load, protection a month after the second Pfizer dose was 90 per cent greater than an unvaccinated individual, reducing to 85 per cent after two months and 78 per cent after three.

For AstraZeneca, the equivalent protection was 67 per cent, 65 per cent and 61 per cent, the researchers said.

Dr Koen Pouwels, senior researcher at the University of Oxford’s Nuffield Department of Population Health, said that the team 'can be confident' that the numbers 'really represent a decline' for the Pfizer vaccine, whereas for AstraZeneca 'the differences are compatible with chance, that is there could be no change at all in the protection from AZ'.

ALSO READ: The least and most vaccinated areas in Oxford

But he added: “Even with these slight declines in protection against all infections and infections with high viral burden, it’s important to note that overall effectiveness is still very high because we were starting at such a high level of protection.

“It is also worth highlighting that these data here do not tell us about protection levels against severe disease and hospitalisation, which are two very important factors when looking at how well the vaccines are working.”

Keep up to date with all the latest news on our website, or follow us on Facebook, Twitter and Instagram.

For news updates straight to your inbox, sign up to our newsletter here.

Have you got a story for us? Contact our newsdesk on news@nqo.com or 01865 425 445.