The highly anticipated vaccine (AZD1222) produced by a collaboration between Oxford University and AstraZeneca has become the first to have its interim study data published and appears to be as effective as reported in various media outlets.
A total of 23,848 patients were recruited across the 4 trials and 11,636 were included in the interim analysis. The majority of patients (86%) were aged between 18 and 55 and 12.2% were older than 56 years (those recruited later in the trial). In the trial with an initial lower dose, there were 33 cases of COVID-19, 3 (0.2%) in the test vaccine group and 30 (2.2%) in the control arm, which gave a vaccine efficacy of 90%. among those who received two standard doses, vaccine efficacy was 62.1%.
The authors were unable to explain why a lower followed by a standard dose resulted in higher vaccine efficacy and this is the subject of further work.