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AstraZeneca Vaccine As Third Dose Effective Against Omicron: Study


New Delhi: According to preliminary data released by British-Swedish biopharma major AstraZeneca on Thursday, a third booster dose of the AstraZeneca Vaxzevaria vaccine showed an increased antibody response to the Omicron variant of SARS-CoV-2. 

The vaccine has been jointly developed by Oxford University and AstraZeneca, and is administered in India as Covishield.

The results bode well for India, which has started administering “precaution” or booster doses for healthcare workers and those above 60 with comorbidities. The Centre has said precaution doses will be a third dose of the same vaccine a person has taken — be it Covishield or Covaxin.

In an ongoing safety and immunogenicity trial of the vaccine, it was observed that the Covid-19 vaccine, when given as a third dose, increased the body’s immune response to the Beta, Delta, Alpha, and Gamma variants of SARS-CoV-2, media reports said. 

Third Dose Of AstraZeneca Vaccine: What Did The Trial Find

The vaccine showed an increased antibody response to the Omicron variant, a separate analysis of samples from the trial showed. The results were observed in individuals previously vaccinated with either Vaxzevria or an mRNA vaccine, PTI reported.

“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,” PTI quoted Sir Mene Pangalos, Executive Vice-President, BioPharmaceuticals R&D, AstraZeneca, as saying.

He said that AstraZeneca would continue to progress regulatory submissions around the world for its use as a third dose booster, given the ongoing urgency of the pandemic and Vaxzevria’s increased immune response to the Omicron variant.

Since there is an urgent need for booster doses amid a tsunami of cases driven by the Omicron variant, the company said it was submitting this additional data to health authorities around the world.

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 primary vaccination with CoronaVac (Sinovac Biotech).

AstraZeneca said this data supported 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 that 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, according to the PTI report. 

Quoting Pollard, the report said that 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 safety and immunogenicity trial is called D7220C00001. Its latest update showed that Vaxzevria continued to be “generally well tolerated”. 

In the first half of the year, further analyses from the trial are expected to be released.

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, which is a variant vaccine developed for the Beta variant of the SARS-CoV-2 virus.

Vaxzevria, invented by the University of Oxford, 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 surface spike protein is produced after vaccination, which primes the immune system to attack the SARS-CoV-2 virus if it later infects the body.

The vaccine has received conditional marketing authorisation or emergency use in more than 90 countries. The vaccine is manufactured and supplied by the Serum Institute of India under the name Covishield, under a sub-license agreement with AstraZeneca.

AstraZeneca said that previous studies support Vaxzevria as a third dose booster as part of a homologous or heterologous schedule.

A third dose of Vaxzevria given at least six months after a second dose was observed to significantly boost antibody levels and maintain T-cell response, a sub-analysis from the COV001 and COV002 trials showed.

The third dose also resulted in higher neutralising activity against the Alpha, Beta, and Delta variants, compared with a two-dose regimen.

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, the COV-BOOST trial showed.

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