AstraZeneca-Oxford vaccine candidate shows 70-90% efficacy

The Oxford University-AstraZeneca combine’s vaccine candidate has shown 70-90 per cent efficacy in preventing Covid-19, depending on its dosage.

According to an interim analysis of clinical trials done in the UK and Brazil, “One dosing regimen showed vaccine efficacy of 90 percent when AZD1222 was given as a half dose, followed by a full dose at least one month apart, and another dosing regimen showed 62 per cent efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens resulted in an average efficacy of 70 per cent,” a note from AstraZeneca (AZ) said. The interim analysis was done after 131 Covid-19 cases were reported.

“We have a vaccine for the world,” said Andrew Pollard, Director of the Oxford Vaccine Group, in a global media interaction. Explaining the dosing, where a half-dose was given first followed by a second full dose, he said, it helped “prime” the immune system, though more work needed to be done. Sarah Gilbert, Saïd Professorship of Vaccinology, Jenner Institute, Oxford University, added, that the dosing possibly mimicked the real system, in the way the body responded to a virus.

Normal storage

Pollard further pointed out that their vaccine candidate could be distributed around the world using the regular immunisation distribution system, as it needed normal refrigerated storage conditions (2-8 degrees Celsius).

India’s Serum Institute has a production and distribution alliance on this vaccine for low-and-middle income countries.

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AZ said it will seek an Emergency Use Listing from the World Health Organization for an accelerated pathway to vaccine availability in low-income countries. Company officials, however, did not disclose details on when this was likely to happen.

Pascal Soriot, AZ Chief Executive Officer, pointed out that there were no hospitalisations or severe cases of the disease, in participants receiving the vaccine. On the shorter first doze, he added, it would increase the number doses that become available.

The statement on AZ’s “highly effective” vaccine candidate comes after a string of similar announcements from America’s Pfizer and Moderna and Russia’s Gamaleya Institute, all claiming over 90 per cent efficacy on their vaccine candidates. However, Moderna and Pfizer candidates involve new technology, with the latter posing distribution challenges, requiring storage conditions of -70 degrees.

AZ said it had the capacity to make upto 3 billion doses of the vaccine in 2021 on a rolling basis, pending regulatory approval, it said.

Over 23,000 participants are being assessed presently. Clinical trials are underway in the United States, Japan, Russia, South Africa, Kenya and Latin America with planned trials in other European and Asian countries. About 60,000 participants are to be enrolled globally.