Covid-19: The Vaccine Menu

Yoong Khean
5 min readDec 23, 2020

Author’s note: The Covid-19 series is a series of articles related to the current pandemic.


On Tuesday the 22nd of December 2020, the government of Malaysia announced they have successfully made early purchase agreements for a list of Covid-19 vaccines. The list comprised of:

  • Pfizer-BioNTech vaccine
  • Oxford-AstraZeneca vaccine
  • CanSino Biologics vaccine (finalising)
  • Sinovac vaccine (finalising)
  • Sputnik V vaccine (finalising)

Out of curiosity (and I was procrastinating at work), I made a Twitter poll asking everyone if they had a choice, which vaccine would they take. The results were more or less expected but the reasons behind the choice of vaccine were enlightening.

The Pfizer vaccine won by a mile, at 75% of 1378 votes. The top reason why Pfizer was chosen is due to brand perception and track record of the company, having produced many tried and tested drugs, most famously, Viagra.

For those who are familiar with mRNA technology for vaccines, this is an important reason for some. An mRNA-vaccine is arguably the most ‘precise’ and maybe the safest, from the way it stimulates an immune response. Contrary to popular belief, the technology is not new. Information like this requires a level of scientific literacy and I think this is important to note. With higher scientific literacy, the more information we gather and subsequently the more informed our decision will be.


Another popular reason was that Pfizer was ‘most read about’ and the data was ‘most transparent & reported’. This is an interesting reason and thought I will dig in a bit deeper.

The Pfizer deal by Malaysia was first announced in November 27th and subsequently got approved and distributed by UK and US. Over the past month, Covid-19 vaccine news mostly revolved around it (Moderna vaccine was next to get FDA approval but Malaysia did not negotiate a deal with them). By sheer media exposure alone, almost everyone knew about the Pfizer vaccine, the doses, the side effects and anticipated it to be the first to roll out. Therefore, why most people chose the Pfizer option could be from the mere exposure effect.

The mere exposure effect is basically a psychological phenomenon where individuals show an increased preference for a stimulus as a consequence of repeated exposure to that stimulus. The stimulus, being the Pfizer vaccine and media coverage being the repeated exposure. It didn’t matter that some didn’t know much about the other vaccines but the familiarity of the Pfizer vaccine made them chose it. I think it is somehow like being bombarded with advertisements of a particular brand. Subconsciously, we will choose something we are already familiar with.


The Oxford-AstraZeneca vaccine is the second highest preferred vaccine (13%). Reasons were varied but no less interesting. The science-based reason was top, with most opting for the AstraZeneca vaccine because it uses an Adenovirus as the vector, which is a known method for flu vaccines. Again, it could be familiarity with ‘traditional’ vaccines versus the swanky, high tech mRNA-based vaccines like Pfizer’s that made AstraZeneca’s vaccine the ‘safer’ option. But there were a few surprises as well. One voter mentioned AstraZeneca is charging at cost price (for now), and it was chosen because of that gesture of altruism. So maybe sometimes the scientific details doesn’t matter as much. What matters is how pharmaceutical companies like AstraZeneca, which is still a business entity, appeal to our sense of humanity. Arguably something many large pharmaceutical companies are lacking.

The AstraZeneca vaccine also has a less punishing cold chain requirement. Compared to Pfizer’s vaccine which needs ultra-cold storage at -70°C, the AstraZeneca vaccine can be stored at 2 – 8°C. The difference between the two cold chain requirements is significant and will greatly affect how logistics are planned for storage, transport and distribution. This was also a consideration for some, that the Pfizer vaccine’s requirement is too high and could easily lead to an error in the cold chain handling, ultimately rendering the vaccine ineffective. Therefore, apart from efficacy level & safety profile, the capability of the authorities to store and transport vaccines matter too. Perhaps this is something authorities can focus on when trying to build vaccine confidence.


I will not delve much into the other vaccines since the votes for them were too little by comparison. But by eyeballing, most have trust issues with the Chinese and Russian vaccines. This could be from the lack of data compared to Western-made vaccines, or simply an innate bias towards them. Again, this could affect vaccine confidence. Innate biasses like these could be as irrational as anti-vaccination views and severely impact the vaccine uptake.

I started this article by just exploring the different reasons why people prefer one vaccine over the other. But as I ponder the questions raised by it, I came to realise most of the time we are concerned about why some people refuse vaccinations but less about why people chose to vaccinate.

We assume those who agree with vaccinations will simply accept any vaccine but the poll and the replies tell us otherwise. There are deeper motivations, personal reasons and different levels of scientific literacy which will affect the choice of a vaccine, and subsequently, the decision to vaccinate. I think this is worth exploring further and could help with building vaccine confidence more effectively.

With a mass vaccination being planned using a menu of multiple vaccines, understanding the reasons behind personal choices in vaccination could make or break the 70% population target for the holy grail of achieving herd immunity.



Yoong Khean

Medical doctor by training & an MBA graduate. Has since hung up my stethoscope & currently working in a global health research institute in Singapore.