London: The AstraZeneca Vaxzevaria vaccine showed an increased antibody response to the Omicron variant of COVID-19 after a third booster dose, preliminary data released by the Anglo-Swedish biopharma major said on Thursday.
In an ongoing safety and immunogenicity trial of the vaccine, a formulation developed by Oxford University and administered in India as Covishield, it was found that given as a third dose increased the body's immune response to Beta, Delta, Alpha and Gamma SARS-CoV-2 variants.
A separate analysis of samples from the trial showed increased antibody response to the Omicron variant. The results were observed among individuals previously vaccinated with either Vaxzevria or an mRNA vaccine.
"Vaxzevria has protected hundreds of millions of people from COVID-19 around the world and these data show that it has an important role to play as a third dose booster, including when used after other vaccines, said Sir Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, AstraZeneca.
"Given the ongoing urgency of the pandemic and Vaxzevria's increased immune response to the Omicron variant, we will continue to progress regulatory submissions around the world for its use as a third dose booster, he said.
The company said it is submitting this additional data to health authorities around the world given the urgent need for third dose boosters.
A separate Phase IV trial reported in a preprint with The Lancet' journal showed that a third dose of Vaxzevria substantially increased antibody levels following a primary vaccine series with CoronaVac (Sinovac Biotech).
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AstraZeneca said this data adds to the growing body of evidence supporting Vaxzevria as a third dose booster, irrespective of the primary vaccination schedules tested.
Professor Sir Andrew J. Pollard, chief investigator and director of the Oxford Vaccine Group at the University of Oxford, said: "These important studies show that a third dose of Vaxzevria after two initial doses of the same vaccine, or after mRNA or inactivated vaccines, strongly boosts immunity against COVID-19.
"The Oxford-AstraZeneca vaccine is suitable as an option to enhance immunity in the population for countries considering booster programmes, adding to the protection already demonstrated with the first two doses.
The latest update from the safety and immunogenicity trial named D7220C00001 also showed that Vaxzevria continued to be generally well tolerated.
Further analyses from the trial are expected to be released in the first half of this year. D7220C00001 is an ongoing partially double-blind, randomised, multinational, active-controlled trial in both previously vaccinated and unvaccinated adults to determine the safety and immunogenicity of Vaxzevria and AZD2816, a variant vaccine developed for the prevention of COVID-19 caused by the Beta variant of the SARS-CoV-2 virus.
Vaxzevria was invented by the University of Oxford and 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 spike protein of the SARS-CoV-2 virus, the strain that causes COVID-19.
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.
The vaccine has been granted a conditional marketing authorisation or emergency use in more than 90 countries. Under a sub-license agreement with AstraZeneca, the vaccine is manufactured and supplied by the Serum Institute of India under the name Covishield.
Previous studies support Vaxzevria as a third dose booster as part of a homologous or heterologous schedule, AstraZeneca said.
In a sub-analysis from the COV001 and COV002 trials, a third dose of Vaxzevria given at least six months after a second dose significantly boosted antibody levels and maintained T cell response. It also resulted in higher neutralising activity against the Alpha, Beta, and Delta variants, compared with a two-dose regimen.
The COV-BOOST trial also showed that a third dose booster of Vaxzevria induced significantly higher immune responses compared with controls against the Delta variant and original strain following a primary vaccine series of Vaxzevria or Pfizer/BioNtech.
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