AstraZeneca-Oxford vaccine efficacy data is adding to the good news on vaccine front and establishing that multiple successful vaccines could be available against COVID19. With an average 70 percent efficacy, it is well ahead of the pre-requisite by international regulators like WHO that has put 50 percent as the bar. The company has said protection begins 14 days after the second dose.
What needs to be deliberated is that 2 doses of AstraZeneca vaccine were tried in phase 3 and unlike popular claim that higher dose will lead to higher immune response, here lower doses showed better results -- half dose at first, followed by a full dose that showed nearly 90 percent efficacy.
Indicating that may the higher dose is overwhelming the system, saturating it and efficacy has dropped.
On the mRNA vaccines like Pfizer and Moderna, 3 dosing regimes were tried and the middle one was found to be suitable.
If AstraZeneca goes ahead with the lower dose, more people can be vaccinated with lower vaccine supplies and it would also compare to the other vaccines on the overall efficacy of more than 90 percent --- it looked at 131 confirmed cases of COVID19 to arrive at this efficacy estimate.
However, we still do not know which dosing regime will the company take forward and any differing results on safety in the 2 dosing regimes and how the 131 cases split between the 2 dosing regimens.
The company however has stated that no serious safety events reported and the company will prepare for regulatory submission of the data to authorities around the world.
AstraZeneca vaccine fares better than Pfizer, Moderna or even Sputnik V when it comes to being more heat stable, hence easier and more feasible for countries like India
Large scale manufacturing is ongoing in 10 nations and Serum Institute has indicated 100 million doses of vaccine could be made available by year-end in India
Data for 24,000 volunteers have been analysed so far from trials in the UK, Brazil and South Africa
More details on whether the vaccine works on those infected in the past and efficacy in the elderly are awaited. Also if the vaccine can prevent serious infections or not, these questions need more answers.