Serum Institute on the up as Oxford study backs AstraZ booster for Omicron

Vaxzevria significantly boosts antibodies against the rapidly spreading variant of the coronavirus, shows study

A third booster shot of the AstraZeneca-Oxford Covid-19 vaccine, Vaxzevria, significantly boosts antibodies against the Omicron variant of the coronavirus, said the British drug company.

This brightens the scope for Serum Institute of India (SII) which makes Covishield, the domestic version of the Vaxzevria. Experts believe mixing vaccine shots may give better results in boosting immunity. However, the University of Oxford has supported the use of Vaxzevria as a third booster dose against Omicron. SII is sitting on 500 mn doses of Covishield (half of which is in bulk drug form), and has already cut production by half owing to low demand.

If the vaccine is recommended as a booster against Omicron, it may significantly boost the demand for Covishield in India. An Indian expert group on vaccination policy is yet to take a call on whether and when to allow booster shots against Covid-19.

Vaxzevria was co-invented by the University of Oxford and its spinoff company, Vaccitech. It uses a replication-deficient chimpanzee viral vector based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein. After vaccination, the surface spike protein is produced, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body.

“Neutralisation titres for Omicron were boosted following a third dose with Vaxzevria compared to titres after a second dose. The levels seen after the third dose booster were higher than the neutralising antibodies found in individuals who had been previously infected with and recovered naturally from COVID-19(Alpha, Beta, Delta variants and original strain),” AstraZeneca said.

It explained that sera obtained from individuals one month after receiving the third dose booster vaccination neutralised the Omicron variant to levels that were broadly similar to those observed one month after the second dose against the Delta variant. Two doses of Vaxzevria have been associated with protection against the Delta variant in real world studies, it added.

The study analysed blood samples taken from individuals infected with COVID-19; those who had been vaccinated with a two-dose schedule and a third dose booster; and those who had reported previous infection from other COVID-19 variants of concern. The study included samples from 41 individuals who had received three doses of Vaxzevria.1

The study was performed independently by investigators at the University of Oxford.

“It is very encouraging to see that current vaccines have the potential to protect against Omicron following a third dose booster. These results support the use of third dose boosters as part of national vaccine strategies, especially to limit the spread of variants of concern, including Omicron,” said John Bell, Regius Professor of Medicine, University of Oxford, UK and one of the study investigators.

“Vaxzevria plays an important role in vaccination programmes around the world and these data give us confidence that the vaccine should be given as a third dose booster. It is also important to look beyond antibodies to better understand how vaccines offer protection against Omicron. As we better understand Omicron, we believe we will find that T-cell response provides durable protection against severe disease and hospitalisations,” said Sir Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, AstraZeneca.

Data from another laboratory study support Vaxzevria’s effect against Omicron, with individuals vaccinated with two doses of Vaxzevria retaining neutralising activity against Omicron, although a decrease was seen compared to the original strain.

AstraZeneca is collecting real world evidence evaluating the effectiveness against the Omicron variant with academic groups in the southern African region. AstraZeneca is analysing blood samples from participants in the Company’s Phase II/III trial to evaluate neutralising activity when given as a third dose booster against Omicron for both Vaxzevria and its investigational next generation Covid-19 vaccine, AZD2816.

Data from these studies is expected soon.