AstraZeneca’s COVID-19 Vaccine 82% Effective After Second Dose

February 04, 2021 - AstraZeneca recently announced that its COVID-19 vaccine is safe and effective at preventing coronavirus in Phase 3 clinical trials from the UK, Brazil, and South Africa. 

The first dose of COVID-19 Vaccine AstraZeneca, formally known as AZD1222, elicited vaccine efficiency of 76 percent. After the second dose, protection was maintained. 

With an inter-dose interval of over 12 weeks, vaccine efficiency rose to 82 percent, the company said. Notably, there were no severe cases and no hospitalizations 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,” Sir Mene Pangalos, executive vice president of BioPharmaceutical’s research and development, said in the announcement. 

“Together with the new findings on reduced transmission, we believe this vaccine will have a real impact on the pandemic,” Pangalos continued. 

The UK trial, COV002, assessed the safety and efficacy of the vaccine candidate in 12,390 participants, while the Brazil trial, COV003, enrolled 10,300 participants. Participants in these trials are healthy or have medically stable chronic diseases and are at an increased risk of COVID-19.

The African trial, COV005, enrolled 2,070 participants and enrolled individuals living with or without HIV.

Based on weekly swabs from volunteers in the UK trial, researchers found potential for the vaccine to reduce asymptomatic transmission of the virus.

Specifically, data showed that PCR positive readings were reduced by 67 percent after a single dose and 50 percent after two doses, which shows significant impact on transmission of the virus, AstraZeneca explained. 

Researchers will continue to analyze data to support ongoing rolling reviews for emergency supply. The company is also seeking emergency use listing from the World Health Organization to increase vaccine availability in low-income countries.

“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 authorization,” said Andrew Pollard, professor and chief investigator of the Oxford vaccine trial, and author of the paper.

“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,” Pollard continued. 

COVID-19 Vaccine AstraZeneca can be stored, transported, and handled at normal refrigerated conditions for at least six months. 

The UK was the first country to approve COVID-19 Vaccine AstraZeneca for emergency use at the beginning of January.

The authorization was based on trial results which showed that a two-dose regimen of COVID-19 Vaccine AstraZeneca was safe and effective in preventing symptomatic coronavirus in the UK and Brazil trials.

Specifically, one dosing regimen showed a 90 percent efficacy when the vaccine was given as a half dose, followed by a full dose at least one month apart, while the second dosing regimen showed 62 percent efficacy when given as two full doses at least one month apart.

There were no severe cases or hospitalizations reported more than 14 days after the second dose. 

Days later, COVID-19 Vaccine AstraZeneca received emergency use authorization in India, Argentina, Dominican Republic, El Salvador, Mexico, and Morocco for adults 18 years of age and older.

The approval in India is important not only to enable supply to India, but also to a large number of countries globally.

AstraZeneca partnered with Serum Institute of India (SII), the world’s largest vaccine manufacturer, to supply the vaccine to the Indian Government as well as various low and middle-income countries.