Does Covid-19 Vaccine Efficacy Really Matter? — Dr Musa Mohd Nordin

By CodeBlue | 25 March 2021

Not getting killed by Covid-19, or ending up sick in hospital or ICU, is good enough a reason to grab any currently available Covid-19 vaccine.

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Vaccine efficacy (VE) is the ability of the vaccine to reduce disease in a clinical trial, within the immunised group versus the placebo (unimmunised) group.

In the context of Covid-19, VE is the ability of the vaccine to prevent symptomatic infections, based on the clinical trial data and the attack rate.

Vaccine effectiveness is the ability of the vaccine to prevent disease in the real world. This may be altered by age, medications, co-morbidities, herd effects, etc.

What is the risk of acquiring Covid-19 in Malaysia?

Risk = No of Covid-19 cases in Malaysia / Population of Malaysia X 100%: 336,808 / 32,700,000 X 100%

Risk = Attack Rate = 1.03%

For example, in a vaccine trial in Malaysia with 100,000 vaccinated volunteers, it means that:

When you look at a vaccine with VE of 50 per cent, you would think that 50 per cent will not be protected, i.e. will get Covid-19 (50,000 cases).

Whilst with a VE of 95 per cent, only 5 per cent will get Covid-19 (5,000 cases)

Both are untrue.

In Malaysia, with an attack rate of 1.0 per cent:

Vaccine with VE of 50 per cent, only 0.5 per cent (not 50 per cent) will get Covid-19 (500 cases).

Vaccine with VE of 95 per cent, only 0.05 per cent (not 5 per cent) will get Covid-19 (50 cases).

But what matters more?

The World Health Organization (WHO), the US Food and Drug Administration (FDA) and national regulatory bodies have set a minimum benchmark of 50 per cent VE against symptomatic Covid, before any Covid-19 vaccine can be approved.

Therefore, do not be overly obsessed with VE.

The table below summarises the VE of various vaccines against symptomatic Covid infection, severe Covid diseasea dn Covid-related deaths.

*Data on Sinopharm, Sinovac and CanSino Biologics are preliminary and await verification and validation.

Key Messages

1.    All the vaccines protects against dying from Covid-19.

2.    All the vaccines protect against severe Covid-19 disease. You won’t end up in a hospital or an ICU bed.

3.    The VE varies between the different vaccines.

4.    Not getting killed by Covid-19, or ending up in hospital or ICU is a good enough reason to be vaccinated.

5.    Instead of arguing over VE and which vaccine is better, just get vaccinated and complete the two-dose regimen.

  • This is the personal opinion of the writer or publication and does not necessarily represent the views of CodeBlue.
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