On Monday, AstraZeneca said its AZD1222 vaccine had demonstrated two different levels of efficacy during clinical trials depending on the dosing regimen. The efficacy in patients who were administered two full doses one month apart was 62 percent, while in those administered a half-dose and then a full dose it reached 90 percent. Company representatives later admitted in media interviews that the regimen with higher efficacy was actually a result of a dosing mistake.
"The mistake is actually irrelevant ... Whichever way you cut the data — even if you only believe the full-dose / full-dose data ... — we still have efficacy that meets the thresholds for approval with a vaccine that's over 60% effective," Pangalos said on Wednesday, as quoted by The Wall Street Journal.
According to the official, the fortunate dosing error was discovered when the company checked its vaccine stocks after noticing inconsistencies in the participants' inflammatory reactions.
AstraZeneca has not yet explained how the reduced dose could have produced better results, while the University of Oxford, the vaccine's co-developer, said it would do more research to find this out. The developers now plan to test the more effective regimen on 30,000 volunteers in the United States.
Moncef Slaoui, the chief adviser of US vaccine facility US Operation Warp Speed, has pointed out that the regimen with higher efficacy had only been administered on participants younger than 55 years of age. This batch of participants was also much smaller in size than the one which received two full doses — 2,741 and 8,895, respectively.
Phase 3 clinical trials of the AstraZeneca vaccine are carried out in the United Kingdom, Brazil and India. The trials were put on hold twice after participants developed side effects, including inflammation of the spinal cord and sclerosis.
In October, a volunteer participant in Brazil died after being inoculated with the vaccine, which, nevertheless, did not result in the suspension of trials.