At a time when the world was under siege by the Covid-19 pandemic and everyone was looking out for some sort of medical interventions to shield against the rampant deaths, two vaccines first emerged on the market: AstraZeneca vaccine, designed at Oxford and manufactured by AstraZeneca in the UK, and the Pfizer vaccine, designed at BioNTech (German) and manufactured by Pfizer in the US.
The two are fundamentally different in design. The AstraZeneca vaccine is premised on the traditional technology of using a viral vector as a vehicle to deliver DNA fragments that encode the spike protein of SARS-CoV2, while the Pfizer exploits a more recently (though ingrained within the molecular functioning of cells) adopted technique of deploying the messenger RNA molecules that the body transcribes into spike proteins.
Either way, the issuing spike proteins are presented as immunogens to the body, that ultimately train it to produce antibodies and T cells against the virus. This way, the body is primed to defend itself, in the event of a natural exposure.
During the evaluations for emergence use licensure, the clinical trials data presented showed that the Pfizer vaccine was 95 percent effective while the AstraZeneca was only a meagre 67 percent effective, against preventing severe disease and death.
The low effectiveness of the AstraZeneca vaccine relative to Pfizer at the time led many countries to take the AstraZeneca vaccine as inferior.
Coupled with the EU-UK politics, the AstraZeneca was kicked out of Europe, with many initially procured European doses ending up in Africans countries as donations.
Over the last eight to 12 months, the world has witnessed two experiments in real life, transpire before us.
Two privileged countries each of which first achieved more than 50 percent vaccination coverage for their target vulnerable population have opened up their economies. These are the UK and Israel.
The UK deployed AstraZeneca and Israel deployed Pfizer. The UK cases peaked at 2,000 and started to mysteriously fall.
The cases in Israel have continued to grow and rise. The number of breakthrough infections among the vaccinated in UK is minimal, with almost non hospitalised.
The majority of hospitalised patients in Israel are vaccinated.
While the majority of the elderly populace in the UK remains safe on two doses of AstraZeneca, those above 60 years in Israel must get a third booster.
Ideally, one would wish to say , ‘the writing is on the wall’. The sustained efficacy of AstraZeneca is better than Pfizer but that is not ethically acceptable since these are not cloth labels or race cars on competition.
I have argued that the situation in UK after the European Champions and on-going premier matches relative to that in Israel speaks aloud about the differences in the intermediate to long term efficacy of the two vaccines; AstraZeneca and Pfizer.
For me, it appears the immunity issuing from vaccination with AstraZeneca is more sustained over time than that from Pfizer.
It means people who get Pfizer might need a (3rd) booster sooner than is the case for AstraZeneca. This is biologically expected given the unstable nature of the RNA ( Pfizer) molecule, relative to the DNA molecule (AstraZeneca). The vehicle of delivery too; bio nanoparticles versus viral vectored vehicles might impact the extent of integration and of course stability.
If this were some sports competition, one would inquire whether the Americans and their European allies are willing to concede defeat! Unfortunately this is not a sports game or product marketing competition.
The experiment remains open for further observations before final conclusions or concessions are made.
Dr Misaki Wayengera,
Chairperson ministerial Scientific Advisory Committee on Covid-19