The results of Phase 3 clinical trials of COVID-19 Vaccine AstraZeneca in the United Kingdom, Brazil, and South Africa were released this week in The Lancet, proving the vaccine to be safe and effective, including preventing any severe cases for at least 22 days after the first dose.
All told, from among 17,177 participants, the vaccine provided 76 percent efficacy after just one dose, with protection maintained until the second dose. The longer an interval between doses, the greater the efficacy, with a 12-week interval increasing efficacy to 82 percent. Asymptomatic transmission was also reduced by as much as 67 percent after a single dose.
“These new data provide an important verification of the interim data that has helped regulators such as the MHRA in the UK and elsewhere around the world to grant the vaccine emergency use authorisation,” professor Andrew Pollard, chief investigator of the Oxford Vaccine Trial and co-author of the paper, said. “It also helps to support the policy recommendation made by the Joint Committee on Vaccination and Immunisation for a 12-week prime-boost interval, as they look for the optimal approach to roll out, and reassures us that people are protected 22 days after a single dose of the vaccine.”
The vaccine has an advantage over some of its competitors in that it only needs to be refrigerated, not kept in deep freeze. If stored in this way, it can be kept for at least six months for utilization in healthcare settings.
The vaccine was originally known as AZD1222 when co-invented by the University of Oxford and its spin-out company, Vaccitech. AstraZeneca is now seeking Emergency Use Listing from the World Health Organization to allow the vaccine to accelerate distribution among low-income countries.
“This primary analysis reconfirms that our vaccine prevents severe disease and keeps people out of hospital,” Sir Mene Pangalos, executive vice president of AstraZeneca BioPharmaceuticals R&D, said. “In addition, extending the dosing interval not only boosts the vaccine’s efficacy but also enables more people to be vaccinated upfront. Together with the new findings on reduced transmission, we believe this vaccine will have a real impact on the pandemic.”
Another large trial is ongoing in the United States and abroad, which is expected to enroll up to 60,000 participants.