Maryn McKenna shares the excellent news that midnight August 11 marked one full year with no cases of polio reported in the whole of Africa. It takes three consecutive years of absence for a region to be designated as polio-free but this step is significant nonetheless, given the opposition by Muslim imams in a few countries that nullified the World Health Organization’s goals of making the entire globe polio-free by the year 2000,

It took a little longer than they planned. And in the many setbacks that have kept the world waiting for polio’s death certificate, Africa, and especially Nigeria, played a significant role. There’s an archive of of about 20 posts at my old blog tracing the recent history of polio eradication’s struggles, but here’s the Nigeria piece of the story: In 2003, Muslim religious leaders in Kano state in northern Nigeria began preaching against polio vaccination campaigns, contending that the drops had been deliberately contaminated in a plot to sicken and sterilize children.

(The reasons for the suspicion were complex, but an important factor was Nigerians’ distrust of Western medical interventions, based on a meningitis vaccine trial that took advantage of them. A fictionalized version of that story is told in the book and movie The Constant Gardener; I told the actual story at WIRED in 2011.)

The imams’ opposition triggered massive vaccine refusal, a devastating setback because at the time, Nigeria accounted for half of the world’s polio cases. Shortly afterward it became responsible for many more, because new infections in Nigeria led to a wave of polio cases across Africa, reseeding the disease into countries that had chased it out. So many children went unvaccinated that when a random vaccine-virus mutation occurred, creating an infectious strain, it ripped through Nigeria and border countries in a second epidemic. And in 2011, an independent monitoring board set up to investigate the eradication campaign’s problems excoriated Nigeria (along with India, Afghanistan and Pakistan) for corruption and nonperformance that were keeping the vaccine from needy kids.

But Nigeria managed to turn things around and in a dozen years has made great strides in learning how to overcome religious objections by carefully cultivating the trust of influential people. But the battle is not yet over because religious obscurantism seems to be the one thing that never dies.

Keeping Nigeria and the rest of Africa free from polio will not be easy. Nigeria is the continent’s most populous country; more than 5 million children are born there each year, and vaccinating them could be disrupted by militant attacks or by renewed loss of trust. Last week, for instance, Kenya’s Conference of Catholic Bishops urged followers to boycott the vaccine, making the same claims of contamination and bad intent that were made in Kano 12 years ago.

But let’s celebrate this anniversary for the good news it undoubtedly is.