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AstraZeneca, University of Oxford COVID-19 Vaccine Effective for Disease Prevention, Reducing Spread


A new primary analysis found that the AstraZeneca and University of Oxford COVID-19 vaccine is safe and effective at preventing infection and reducing transmission.



The AstraZeneca and University of Oxford coronavirus disease 2019 (COVID-19) vaccine was found to be safe and effective at preventing COVID-19 in a new primary analysis of clinical trials published in Preprints with The Lancet on February 1, 2021.

In the primary analysis of phase III clinical trials from the United Kingdom, Brazil, and South Africa, University of Oxford researchers found that a single dose of the vaccine (COVID-19 Vaccine AstraZeneca, formerly AZD1222) is 76% effective (confidence interval [CI]: 59%-86%) from 22-to up to 90-days after vaccination. After a second dose, administered after a 12-week interval, efficacy increased to 82.4% (CI: 63%-92%).

There were no severe cases or hospitalizations recorded more than 22 days after the first dose.

“This primary analysis reconfirms that our vaccine prevents severe disease and keeps people out of hospital. 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,” said Menelas Pangalos, executive vice-president, BioPharmaceuticals R&D, AstraZeneca, in a company press release.

The primary analysis included 17 177 study participants aged ≥18 years accruing 332 symptomatic cases from the ongoing UK, Brazil, and South Africa trials, 201 additional cases than previously reported. Participants were randomized to receive 2 standard doses of either the COVID-19 Vaccine AstraZeneca or a control vaccine.

In addition to demonstrating vaccine efficacy of 76% after a first dose, the results showed vaccine efficacy increased to 82% (CI: 63%-92%) with an inter-dose interval of ≥12 weeks.

Also, the results showed the vaccine’s potential to reduce asymptomatic transmission of COVID-19, based on swabs obtained from the participants in the UK arms of the study. The data showed that PCR positive readings were reduced by 67% (CI: 49%-78%) after a single dose, and 50% (CI: 38%-59%) after 2 doses.

Researchers will continue to analyze data from the ongoing clinical trials, and AstraZeneca plans to get Emergency Use Listing from the World Health Organization to make the vaccine available in low-income countries, noted the press release.

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