Terrible news.

Gunmen suspected of belonging to a radical Islamic sect shot and killed at least nine women who were taking part in a polio vaccination drive in northern Nigeria on Friday, highlighting the religious tensions surrounding the inoculation of children in one of the few nations where the disease still remains endemic.

The attack shocked residents of Kano, the largest city in Nigeria’s predominantly Muslim north, where women often go from house to house to carry out the vaccination drives as Muslim families feel more comfortable allowing them inside their homes than men. It also signaled a new wave of anger targeting immunization drives in Nigeria, where clerics once claimed the vaccines were part of a Western plot to sterilize young girls.

The first attack Friday morning happened in Kano’s Hotoro Hayi neighborhood and saw gunmen arrive by three-wheel taxis and open fire. At least eight female vaccinators died in that attack, witnesses said.

These attacks come on the heels of a series of assassinations of health workers in Pakistan in recent weeks, where at least nine polio workers have been murdered.

Boko Haram — the local islamist insurgency — is believed the be responsible for the attack. That would make sense because there has been suspicion about the polio vaccine from conspiracy minded extremists for years. The CIA fed these theories when it used a vaccination campaign as ruse to collect intelligence on Osama Bin Laden. I fear what we are seeing now is blowback from that unfortunate decision.

The rub here is that humanity is so very close to eliminating polio from the face of the earth. In a major global health milestone in 2012, India went one full year without a new polio infection. Now, there are only three countries left on the planet where it remains endemic: Nigeria, Afghanistan and Pakistan. Defeating polio worldwide means defeating polio in these three holdouts. And defeating polio in these holdouts requires near universal vaccination rates for several years.

Health workers are not going deliver the oral polio drops at the point of the gun, so any violence against them severely limits their access to the very populations that need them the most.

The attacks in Nigeria suggest that Islamist inspired terrorist groups are opening a new, global front against health workers.  If so, the global polio eradication campaign could face a perilous setback, putting children at risk all around the world. A systematic campaign of terror against polio workers worldwide means that humanity could be burdened with this disease for many years longer than we have to.