Why Covid-19 vaccine can't be supplied quickly?

With demand for Covid-19 vaccines outpacing the world's supplies, a frustrated public and policymakers want to know : How can we get more? A lot more. Right away.

No Room For Error

Makers of Covid-19 vaccines need everything to go right as they scale up production to hundreds of millions of doses - and any little hiccup could cause a delay. Some of their ingredients have never been produced at the sheer volume needed.

Raw Materials

Production depends on enough raw materials. Pfizer and Moderna insist they have reliable suppliers. But the Moderna CEO acknowledges that challenges remain. With shifts running 24/7, if on any given day "there's one raw material missing, we cannot start making products and that capacity will be lost forever because we cannot make it up", he recently told investors.

And sometimes the batches fall short. AstraZeneca told an outraged European Union that it, too, will deliver fewer doses than originally promised right away. The reason cited : Lower than expected "yields", or output, at some European manufacturing sites.

Different Vaccines, Different Recipes

The multiple types of Covid-19 vaccines being used in different countries all train the body to recognise the new corona virus, mostly the spike protein that coats it. But they require different technologies, raw materials, equipment and expertise to do so.

Scaling Up

The two vaccines authorised in the US so far, from Pfizer and Moderna companies, are made by putting a piece of genetic code called mRNA - the instructions for that spike protein - inside a little ball of fat.

Making small amounts of mRNA in a research lab is easy but "prior to this, nobody made a billion dosesor 100 million doses of mRNA", said Dr Drew Weissman of the University of Pennsylvania, who helped pioneer mRNA technology.

Scaling up doesn't just mean multiplying ingredients to fit a bigger vat. Creating mRNA involves a chemical reaction between genetic building blocks and enzymes, and Weissman said the enzymes don't work as efficiently in larger volumes.

Variability

AstraZeneca's vaccine already used in Britain and several other countries and one expected soon from Johnson & Johnson, are made with a cold virus that sneaks the spike protein gene into the body. It's a very different form of manufacturing : living cells in giant bioreactors grow that cold virus, which is extracted and purified. "If the cells get old or tired or start changing, you might get less", Weissman said. "There's a lot more variability and a lot more things you have to check".

We think, 'Well, OK, it's like men's shirts, right? I'll just have another place to make it. "It's just not that easy" - a vaccine adviser to the US Government.

Courtesy. TNIE, 31 Jan.

My take

Now you can understand how systematically the Covaxin and Covishield vaccines have been manufactured in India. We need to be proud of our achievements!

Tailpiece.

Got up half an hour late, the chores and was ready by 10. It was a normal day.

Sathi Amma's 41st day ceremony. Lunch was sent across, for us, by her daughter - a diktat that she'd received from her mother!