Wonderful as it is to recall the glories of the manned space program — the exhilaration and sense of infinite possibilities for humanity — there were also setbacks, disasters and disappointments.

Something similar is happening now with polio and the world’s longest and most ambitious quest to eradicate the poliovirus, which is highly contagious, largely strikes children under 5 years old and can cause permanent paralysis.

Thanks to vaccination, the eradication effort is closer to success today than at any time in 30 years. Yet all of a sudden, a new outbreak has appeared in Syria. Is the goal about to be lost?

Not exactly, but the mixture of optimism and worry is warranted. As recently as the mid-1980s, polio paralyzed more than 350,000 children a year in 125 countries where it was endemic. As Microsoft founder and philanthropist Bill Gates pointed out recently, that’s 40 cases an hour. By contrast, so far this year, the last three endemic countries have reported a total of only six cases of wild poliovirus, fewer than at any moment ever: four in Afghanistan and two in Pakistan, and none so far this year in Nigeria. This is an extraordinary accomplishment by people, biomedicine and philanthropy. Just a few years ago, Pakistan, for example, appeared to be spinning out of control, with vaccination workers murdered while on the job and whole sectors beyond reach of immunization. Globally, some 16 million people are walking today who might otherwise have been afflicted with paralysis.

The numbers are so low today that eradication may indeed be within reach, if there is not another setback in the remaining endemic countries. For this, immunization and surveillance must be sustained. On June 12, philanthropists and governments once again backed the Global Polio Eradication Initiative, a public-private partnership aimed at the second-ever eradication of a disease, after smallpox.

At the Rotary International convention in Atlanta, $1.2 billion was pledged. Up to $150 million raised in the next three years by Rotary International, which has been at the forefront of the battle since 1985, will be matched 2-to-1 by the Gates Foundation, which pledged a total of $450 million, including the match. The remaining amount will come from other donors, all to make sure there is no relapse and a final fight to the finish.

The one dark spot is Syria, where a fresh outbreak has paralyzed 17 children, most from Mayadin, south of Deir al-Zour, and one child from Raqqa.

Fortunately, there is an effective vaccine and a fair amount of experience in extinguishing such an outbreak, and with enough effort and immunization, it can be contained.

The moonshot may yet succeed.