Photo: The Canadian Press

A health-care worker prepares a dose of the Pfizer-BioNTech COVID-19 vaccine at a UHN COVID-19 vaccine clinic in Toronto, Thursday, Jan. 7, 2021. A single dose of Pfizer-BioNTech's COVID-19 vaccine is barely enough to cover the average pinky nail but is made up of more than 280 components and requires at least three manufacturing plants to produce.

A single dose of Pfizer-BioNTech's COVID-19 vaccine is barely enough to cover the average pinky nail but is made up of more than 280 components and requires at least three manufacturing plants to produce.

By the time that dose is injected, it has travelled to at least six different cities in four countries, across the Atlantic Ocean twice, and monitored by a 24-hour watchtower in Iceland every step of the way.

A marvel of both science and supply-chain heroics takes the vaccine from the factory floor to the arms of grateful patients all over the world.

"It's really very complex," said Germain Morin, Pfizer's vice-president in charge of global supply chains for the company's rare-disease medications and vaccines.

The messenger ribonucleic acid (mRNA) vaccines being made by Pfizer and its German partner BioNTech, as well as Moderna, are a novel technology that before COVID-19 had never been approved for widespread use in humans.

While DNA is the large and complex molecule that stores all of genetic coding that makes us who we are, RNA carries individual pieces of that code out into the body with the instructions on how to carry out the body's work.

In the case of mRNA vaccines, they are carrying the genetic code for part of the SARS-CoV-2 virus, which teaches our bodies to mount a defence against the virus.

A year ago, the materials for these vaccines were being made for research purposes only, enough for maybe a few hundred doses at a time. Now Pfizer expects to pump out two billion doses by the end of this year.

It has made scaling up the manufacturing process a herculean feat, said Morin. There are 25 different suppliers involved, spanning 19 different countries. Some of them, said Morin, were making milligrams of liquid at the start. Then they were asked to make kilograms of it, and finally hundreds of kilograms.

The 475,000 doses Canada received last week began their lives before Christmas. Morin said it used to take four months to make a single dose of the vaccine, which is officially called BNT162b2. Morin said the process has recently been streamlined to half that time.

Every dose of the Pfizer-BioNTech vaccine is born in a Pfizer lab in Chesterfield, Mo., a suburb of St. Louis. That's where small DNA molecules called plasmids are made with the beginnings of the code for the SARS-CoV-2 spike protein.

It takes about two weeks, followed by a quality assurance process. Every step of production has quality checks and rechecks, from the bags and boxes used to store and transport the vaccine components to the temperature in the lab and the protective clothing worn by any workers.

Then comes the first major chill, as the plasmids are put in bags and frozen to that famous ultralow temperature Pfizer's product needs: -80C.

From Missouri, the plasmids are shipped to two labs, one a Pfizer facility in Andover, Mass., and another a BioNTech facility in Germany, where they are used to make the mRNA.

A single batch of mRNA takes about four days to make, in a high-tech process with numerous enzymes and chemicals. The mRNA is then frozen again and shipped off for finishing.

In the U.S. that happens in Kalamazoo, Mich., and for Canada's doses, currently made in Europe, they go to Puurs, Belgium, Pfizer's biggest plant in the world.

Messenger RNA is not a very stable product and will disintegrate quickly if not protected, so every bit of mRNA is encased in a tiny amount of fat called a lipid nanoparticle.

"Imagine a very, very small egg, so a very small eggshell of lipids that would protect the mRNA," said Morin. "This is part of the magic of making this vaccine as well."

Over the course of three or four more days the mRNA gets its lipid coating, and is filled into vials containing enough vaccine for six doses. The vials are then packed into boxes, and immediately put into "those famous freezers" which turn the lipid-coated mRNA molecules into mini blocks of ultracold ice.

"This was, by the way, one of the challenges," said Morin. "You can imagine that those freezers are not very common in the world. Laboratories buying them would typically buy them one or two at a time. We went to the suppliers and the first time we've asked for 650 of them in one shot, and then we went for more after that."