Oxford/AstraZeneca booster works well, study finds

A study has found that the Oxford/AstraZeneca Covid-19 vaccine works well as a third booster shot, despite concern that the immune system might fight off the adenovirus used as a delivery mechanism.

A third dose was shown to boost participants’ antibodies to the coronavirus’s spike protein in an upcoming study by Oxford university, according to people familiar with the matter.

Some scientists have feared that repeated use of the adenovirus vector — an inactivated cold virus — could stop the immune system recognising the virus’s spike protein.

The study found the participants’ immune systems did react to the adenovirus used to deliver the protein — but it had a far more significant reaction to the protein, according to one of the people.

Another person familiar with the trial results described the antibody reaction to the booster shot as “unbelievable” and strong enough to “blow through almost any variant”.

“It kills all these arguments that you can’t use adenoviruses more than once,” they said.

The study strengthens the case for using the AstraZeneca vaccine as a booster shot if the immunity in participants begins to wane over time, or if it would help the body fight new variants of the virus behind Covid-19. Oxford and AstraZeneca did not comment. It is not known when they plan to publish the data. 

Another person familiar with the study said it showed delaying the third dose gives “very high antibody” response. 

“It’s a little bit surprising because they keep over-focusing on the carrier virus that you get immune responses to. This data shows you need to stop worrying about that,” the person said. 

AstraZeneca, which did not have a vaccine business before it partnered with Oxford on the Covid-19 shot, could sell the vaccine as a booster shot on an annual market that analysts estimated last year could be worth about $10bn. Rivals including BioNTech/Pfizer and Moderna are already signing pre-orders for their vaccines for 2022.

The Anglo-Swedish drugmaker has agreed to make the vaccine available on a non-profit basis during the pandemic, but could profit from sales in developing countries after it is over. The company has not yet laid out a commercial plan for the product, whose reputation has been damaged recently by the emergence of rare, but sometimes fatal, side effects.

Adenovirus vaccines including the AstraZeneca, Johnson & Johnson and Sputnik shots use inactivated cold viruses to deliver the viral protein from Sars-Cov-2 to teach the immune system to make antibodies.

Several scientists have raised concerns that adenovirus vectors are not well suited to booster programmes. Marie-Paule Kieny, director of research at Inserm, the French National Institute of Health and Medical Research, said earlier this year that “most people think there will be less flexibility with adenovirus vaccines”.

“We will end up having so much immunity against the adenovirus that we will not be able to vaccinate every year,” she said. “With [rival technology using] mRNA there is no anti-vector reaction.”

Sputnik uses two different adenoviruses in its first and second shots, in an attempt to ensure the body recognises both the protein and the vector on the second round. 

Others have suggested that vaccines should be mixed, so people who received an adenovirus vaccine at first may get boosted with another type. However, a UK trial result out last week suggested that mixing vaccines could increase the risk of short-term side effects such as fever and fatigue. 

Additional reporting by Clive Cookson in London

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