The COVID-19 vaccine that gained full approval Monday came quickly. But it did not come out of nowhere.

The Pfizer-Biotech shot may have been approved on an expedited timeline. But it is the result of a decades-long effort to build a better vaccine, which itself was guided by long-established science.

It took an untold number of people working countless hours in labs, building on the knowledge that came before them, to make the vaccine, which is now doing just what it was intended to do: prevent the spread of COVID, and keep people out of the hospital.

Simply put, the vaccine is meeting this moment in history, and if it came just in time, that is only because of the work that preceded the pandemic.

Pfizer, an American company, and Biotech, based in Germany, first partnered in 2018 to take advantage of research showing the potential for vaccines based on messenger RNA rather than versions of the virus itself. They were far from the only ones; competitors included Moderna, which formed in 2010 specifically to pursue the new technology.

But the road to an approved vaccine goes back even further.

Messenger RNA, or mRNA, had been discovered in the early 1960s after more than a decade of study. Later, it showed therapeutic potential, with big breakthroughs revealing that it could direct the body how to fight off a virus — if only it could be delivered into the body in a stable form.

The first successful use of a mRNA vaccine came in 1990, on animals. But stabilizing the mRNA for delivery into the body proved difficult, and most attention continued to go to developing vaccines through traditional means.

Not everybody gave up on mRNA, however. Because mRNA vaccines could be created and produced faster than others, it had tremendous potential for fighting an emerging virus. Another breakthrough was all that was needed.

That breakthrough came in 2005 out of the University of Pennsylvania, where two researchers who had been working on mRNA since the 1980s found a way to inject it and elicit an immune response. It was their technique that was licensed by Pfizer, Moderna and others as they developed mRNA technology to use against a variety of diseases.

In addition to the work by the pharmaceutical companies, the drive for a vaccine was helped by a network of experts who had gained experience from years of studying HIV, cancer and the flu.

Without this capacity already in place, the vaccine would have never come so quickly. To be sure, it was a decades-long commitment to science that brought us the vaccine, along with the billions of dollars provided by federal government, starting with the Trump administration.

And what has the vaccine brought us? More than 200 million shots of the Pfizer vaccine have been administered in the U.S., with hundreds of millions more worldwide.

With all this experience already — Pfizer’s FDA application comprised 360,000 pages, more than any other previously approved vaccine — we can say some things with confidence.

First, the shot is exceedingly safe; there have been no U.S. deaths linked to it.

Second, getting the shot greatly reduces one’s chance of getting COVID-19, and nearly eliminates the potential for a severe infection.

It’s doing just what it’s supposed to do — just what the researchers thought and hoped it would do as they developed the technology in fits and starts through the decades.

But you have to get the shot for it to work, and as of this writing about 85 million eligible Americans have not taken advantage.

Now that the vaccine is fully approved, we hope many of them will change their mind. It’s now their turn to meet the moment, for their own health and the health of their neighbors.