Unravelling COVID vaccination efficacy

The way COVID-19 vaccines protect us is still not fully understood. Nor is the level of protection achieved by the various vaccines. Studies are now emerging highlighting the confusion in the community about what constitutes vaccine efficacy. There is a common misconception that vaccine efficacy is measured by the vaccine’s ability to prevent us from contracting COVID-19.  That is not true. 

Vaccines will become less and less of the story

Vaccine efficacy should be recorded as the percentage of individuals who develop COVID-19, comparing the vaccinated group to the non-vaccinated group. This would allow us to easily compare vaccine success rates.  However, all the vaccine trials have been constructed so these kinds of direct comparisons are difficult to make.

Let’s first look at outcome measures of successful vaccination. Pfizer, Astra Zeneca, the Indian Covaxin and the Chinese Sinopharm all measure efficacy against hospitalization. All of them are 100% effective against hospitalization. But they all examine a different number of days from infection to assess hospitalization. Johnson&Johnson uses efficacy against “severe disease” as its outcome and the Russian Sputnik V does not share its efficacy data

The efficacy arena is a cacophony, with no two drug companies speaking the same language.

Early in pandemic, the number of mutant — or variant viruses was low. The number of people who were infected with the virus was small and there were consequently fewer opportunities for mutations. The enormous number of infections has led to the evolution of multiple SARS-CoV-2 variants.  Another factor that has resulted in development of additional variants is the prolongation of infection, for example in individuals with chronic illnesses that inhibit their ability to mount a normal immune response.

Anyone who has been watching the arrival of mutations knows that they will have to start using other alphabets soon.  There are only 24 letters in the Greek alphabet, and with WHO already worried about the mu variant ( 12th letter in the Greek alphabet), only a dozen more letters remain.  Mu has made its debut only a short time after we heard about the delta variant (4th letter). 

It is true all companies are conducting studies to show how their vaccines are effective against the emerging variants, albeit only in the laboratory. If we have learned anything from the delta variant, it is that COVID is a survivor virus and will continue to mutate into more infective forms rather than lethal ones that would kill off their hosts, that is, us. It follows that vaccines will become less and less of the story and our own internal defence mechanisms will become more important – that is until an effective and affordable early treatment emerges. Unfortunately, there is no penicillin equivalent on the horizon nor much appetite from pharma to research one. 

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