Polio outbreaks in the Middle East and Africa could spread to Europe if precautions aren't taken, researchers say.
The recent discovery of the poliovirus in Syria, Somalia and Israel should be a wake-up call for European health officials, according to epidemiologist Martin Eichner at the University of Tuebingen in Germany.
"There are more and more countries where polio is being transmitted, and there are more and more routes for the infection to make its way back to Germany," Eichner tells Shots. "We should be more careful."
Europe is at risk for two reasons, scientists say. Polio vaccination rates have fallen on the continent. And Western Europe uses the inactivated polio vaccine, known as IPV.
"Someone with IPV protection can still be infected and still to some lesser degree pass on the infection," Eichner says. IPV is highly effective at protecting people from getting sick, but not as good as the live oral polio vaccine at stopping transmission of the virus.
Polio vaccination rates in some parts of Europe are dangerously low, Eichner and his colleague wrote Thursday in a letter in the journal The Lancet. For instance, Ukraine has only 74 percent of its population fully immunized; Austria reports 83 percent.
Europe struggled for decades to get polio under control. In 1998 the last non-imported case of polio was reported in a child in Turkey. The continent was certified as polio-free in 2001, according to UNICEF.
But that certification doesn't mean that Europe is invulnerable.
Eichner and his colleague also analyzed regional polio vaccination rates across Europe and found wide variations in coverage inside some countries. He suspects that there could be geographical pockets inside Austria, for instance, where vaccination rates are far lower than the national rate.
"The worry is that transmission could reach one of these groups and then spread much more readily," he says.
The European Centre for Disease Prevention and Control has recommended that countries focus on ensuring that all Syrian refugees who enter the European Union are fully vaccinated against polio.
But Eichner says this precaution alone may be insufficient to prevent an outbreak. Raising vaccination rates in Europe throughout Europe is the surest protection, he adds.