Although UK is in the grip of an heightened emergency scenario with the Covid-19 new infected cases hovering around the 50,000 mark daily due to the new variant which is 70% more transmissible, the decision by the British government to use a mix of the Pfizer/BioNTech and AstraZeneca/Oxford vaccines as an emergency measure is a gamble that may have serious consequences.
Even if the two vaccines are based on the same messenger RNA concept, still the clinical trials of these respective vaccines have been done only for 2 doses of the same vaccine within a 21-day period and the efficacy has been determined only for inoculation with the same vaccine that are coincidentally about 95% effective.
UK could have used both the vaccines but subjected those inoculated with the same brand shots. This would have reduced the unknown factor of mixing the two vaccines as an emergency measure which could have unknown untested effects. It would have been definitely better to vaccinate people with the same shots of each vaccine instead of trying a combination of the two which has unknown degree of clinically untested efficacy of use in tandem.
Anyway the number of shots will only totally add up to the number of shots of each vaccine that can be manufactured for deployment at the particular time. Even a small difference in the composition of the two vaccines could have unknown consequences and be a gamble on the lives of the recipients. Also efficacy of the respective vaccines has been tested for previous strain of coronavirus and not for the new strain which is 70% more transmissible.
ELVIDIO MIRANDA, via email
