AstraZeneca booster raises antibodies against Omicron less than Pfizer, study shows

A third dose of the Oxford/AstraZeneca Covid-19 vaccine increases antibody levels against the Omicron coronavirus variant far less than a BioNTech/Pfizer booster, a study has shown.

A new laboratory study from researchers at Oxford university found that an AstraZeneca booster raised antibodies 2.7-fold, while a third dose of the Pfizer jab increased the levels 34.2-fold, a month after vaccination.

But the researchers noted that the third dose of AstraZeneca increased antibody levels against Omicron to the same point as two doses did against the Delta strain, which had proved protective in real-world studies.

Antibody levels elicited by the third dose were higher than those in people who had previously recovered from Covid caused by other strains.

Sir Mene Pangalos, AstraZeneca’s executive vice-president, said the vaccine plays an “important role” around the world and the data give us “confidence that the vaccine should be given as a third dose booster”.

The vaccine is not being used as a booster in the US, Europe or UK, but could be useful in low- and middle-income countries where it has powered immunisation campaigns.

Pangalos said it was important to look beyond antibody levels to other parts of the immune system including the T cell response, which may be more durable and protect against severe disease and hospitalisation. T cells are the key white blood cells of the immune system.

Before the Omicron wave of infections, AstraZeneca’s chief executive Pascal Soriot suggested that the T cell response to its vaccine might have stopped the UK from experiencing the same high level of hospitalisations as other countries, which used it less. But he said more data were needed. T cell levels are harder to measure than antibodies.

The company also reported that its long-acting antibody treatment could still tackle the Omicron variant. The drug known as Evusheld combines two potent antibodies as a preventive measure.

Pangalos said AstraZeneca was “excited that Evusheld is now available to help protect vulnerable populations, such as the immunocompromised, who are unable to mount an adequate response to vaccination and who remain at high-risk for Covid-19”.

Oxford and AstraZeneca have taken preliminary steps to tweak the vaccine for the Omicron variant, in case a targeted version of the shot is needed, following other vaccine makers.

Despite suffering setbacks including problems with production and concerns about a very rare blood clotting side effect, AstraZeneca is pressing ahead with its jab, creating a new unit for vaccines and immune therapies.

But a peer-reviewed paper published in The Lancet earlier this week, based on data from before the Omicron variant emerged but while Delta and Beta were circulating, showed the protection from two doses began to wane within three months of the shot.