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Ho Ching, who will retire as CEO of Temasek Holdings on Oct. 1, has explained how the immunisation process behind a mRNA Covid-19 vaccine functions, such as that made by Pfizer-BioNTech.

Quoting the former director of the U.S. Centers for Disease Control and Prevention, Tom Freiden, she called on Singaporeans aged 60 and above to think of the vaccine as a "special biodegradeable recorder tape" with instructions for the body on how to make the spikes of the virus.

Ho said:

"So an mRNA vaccine is like a self destruct or biodegradable messenger carrying instructions to make the most important bit, the spike, for our immune system to recognise and learn to fight."

Covid-19 vaccinations for seniors will begin islandwide next Monday (Feb. 22).

Seniors aged 70 years and above are expected to be able to receive their vaccinations by mid-March, following which seniors between the age of 60 and 69 will begin being vaccinated.

So why is the body instructed to make the spikes of Covid-19?

According to Ho, the spikes are the critical bit of the virus which stick to our cells so that the virus can enter the cells to make more copies of itself to multiply an infection.

However, the spikes themselves do not actually cause an infection.

Rather, once the body's cells begin manufacturing the spikes of the virus on their surfaces, the body recognises the spikes as an infection and will begin responding as such.

Ho said:

"Various cells and other bits of our immune system will start to swarm towards the injection spot where these mRNA have activated the local cells to start producing the spikes."

She added that part of the response includes making neutralising antibodies (NAbs).

"These NAbs recognise the spikes, and lock onto these spikes in a tight bear hug so that the spikes are prevented from attaching themselves to our cells."

And how exactly are the instructions conveyed to the cell?

Ho then turned to addressing how the instructions are conveyed to the cell.

Here, she highlighted that the biodegradable "tapes" of mRNA instructions are wrapped within fatty bubbles protect them for a little more, and help them enter the body's cells.

Without the bubbles, the "tapes" will disappear quickly, she added.

As for the cells, they have "tape recorders" which allow them to read the mRNA instructions to begin producing the spikes.

Sides effect show that immune system is reacting

This brought up her next point that the side effects of the vaccine show that the immune system is reacting and organising themselves.

Ho then pointed out that the key phase of the body's immune system response occurs around the second and third week once the "B cells and T cells get into action."

The T cells in particular will fashion killer T cells that will hone in on the cells with the spike, so as to kill them before more copies of the virus are made, she said.

"The killer T cells are the homing missiles. They recognise that any of our cells showing spikes on their surfaces are 'infected' and 'alien', who have been hijacked to produce more viruses.

They home in to kill the infected cells before more copies of the virus are made."

The vaccine needs to be frozen as mRNA is short-lived

In addition, the need to have the vaccines frozen is to help prolong the lifespan of the virus' mRNA.

On this matter, Ho noted that mRNA produced within the human body is shortlived, with half of it disappearing within 48 hours and the remainder within the next few days.

Ho then highlighted how the delivery process of the vaccine had to account for this need by laying out the following steps:

• The vaccines must first be warmed to fridge temperatures at vaccination centres, whereupon they can be stored a few days in normal fridges,
• Afterwards, the vials of concentrated mRNA vaccine are taken out from the fridge to be diluted in to five or six doses,
• These diluted vaccines must then be used within six hours, as the mRNA will start to degrade and eventually become useless, even with their fatty bubbles,

The vaccines must also ideally be extracted into syringes, she said, and kept within kidney trays that are stored in the fridge of cooler bags to be ready for administration to the general public.

The Prime Minister's wife concluded by reiterating that vaccination is not compulsory and that people will still be subjected to a medical interview at the vaccination centre to determine if they are eligible to go through with the jab.

Here is her post in full:

More about the different types of vaccines:

Left image from Ho Ching Facebook, right image from Unsplash