Reports are emerging from all over the world of successful vaccines for COVID-19. This is encouraging as a vaccine is a core part of our ‘exit’ strategy for this pandemic as it could make the population immune to COVID-19, thereby allowing life to return to normal. But which vaccine do we choose? Tens of different vaccines are being developed concurrently and we have been inundated with preliminary results from phase three trials of four different vaccines from the following four companies: Oxford University/AstraZeneca, Moderna, Pfizer/BioNTech and Gamaleya.
The table below shows a comparison of the four vaccines and their ‘claimed’ effectiveness after preliminary trials.
What does the effectiveness value tell us?
The effectiveness value is the likelihood of not developing COVID after taking the vaccine. If you went on that alone, the Moderna and Pfizer/BioNTech vaccines would clearly win. However, all trials are conducted differently with health, speed, and ultimately finance at the forefront of the company's mind. If the trials are different, is it possible to compare like for like? When giving a vaccine, is effectiveness all that matters?
How do we analyse the data?
A closer look at the Oxford results shows that their trial consisted of two different types of treatment regimens. One group of participants received two full doses of the vaccine given a month apart, and another group were given half a dose first which was then followed by a full dose a month later. Remarkably, they report the full dose/full dose regimen to be only 62% effective compared to 90% in the half dose/full-dose regimen. How do we interpret these results? Should we take the lower or higher value or their average effectiveness which they say is 70%? Why is it important to consider the fact that half dose/full-dose group had far fewer participants? What other obstacles may the companies have experienced when conducting the trials? How may this affect the results?
Do the types of vaccine make a difference?
Ultimately, yes. The type of vaccine impacts the cost, preparation times, immune response, side effects, storage and potentially the effectiveness of the vaccine. The table shows how each vaccine must be stored. Reading these results, which vaccines would be difficult to deliver logistically? How could we deliver these effectively?
Oxford University/AstraZeneca Vaccine: https://www.nature.com/articles/d41586-020-03326-w
Moderna Vaccine: https://www.bmj.com/content/371/bmj.m4471
Pfizer/BioNTech Vaccine: https://www.nature.com/articles/d41586-020-03166-8
Gamaleya/ Sputnik V Vaccine: https://www.ft.com/content/83e7b65d-89cb-48f8-a42c-0d528236a122