In a press release today, AstraZeneca reported its AZD1222 vaccine against SARS-CoV-2 is ready to report efficacy levels.
Oxford University Covid-19 vaccine can protect 70% of people from developing symptoms https://t.co/UJwdjErq5q
— ITV News (@itvnews) November 23, 2020
BREAKING: Trials of Oxford's AstraZeneca #COVID19 vaccine shows it is up to 90% effective in preventing the virus.
— SkyNews (@SkyNews) November 23, 2020
More on this story: https://t.co/gH4tyBF6cv pic.twitter.com/yu7PyUAUqS
As the two tweets above demonstrate, the two very different figures of 70% and 90% came out by separate news agencies. The discrepancy, it turns out is related to variations in how the vaccine is administered.
The variations are summed up by AstraZeneca in the original press release:
One dosing regimen (n=2,741) showed vaccine efficacy of 90% when AZD1222 was given as a half dose, followed by a full dose at least one month apart, and another dosing regimen (n=8,895) showed 62% efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens (n=11,636) resulted in an average efficacy of 70%.
Shortly after initial announcements, some news agencies moved to clarify the confusion in response to negative public perception of media integrity.
Oxford and AstraZeneca Covid19 vaccine is between 62% and 90% effective - with difference in efficacy related to how the two necessary doses were administered pic.twitter.com/uPAsaY69q1
— Robert Peston (@Peston) November 23, 2020
AstraZeneca closely follows the announcement by Pfizer who with the firm BioNTech released news of a 90%+ effective vaccine.
Following Pfizer's announcement, several members of the Trump family and administration credited the US president's Operation Warp Speed's "tireless work" to support the creation of the vaccine. However, Pfizer was only a participant in the program in terms of a conditional purchase agreement, rather than funding.