When the number of Syrians fleeing their war-torn state to live in neighboring countries topped two million, the United Nations refugee head called the situation a "humanitarian calamity." Now it is getting worse, with the potential for the refugees to carry polio across the Middle East and Europe causing alarm.
A letter to The Lancet by German epidemiologists outlines what is at stake. The epidemiologists fear the arrival of asymptomatic Syrian refugees infected with wild-type poliovirus 1 into Europe, a region that uses the imperfect inactivated vaccine and has clusters of unimmunized people, will spark a silent outbreak. With 99% of infected, unvaccinated people never developing acute flaccid paralysis, the virus could spread from the refugees into the local population without health authorities noticing.
The epidemiologists view the use of inactivated polio vaccine (IPV) as part of the problem. IPV prevents many cases of acute flaccid paralysis, but only offers partial protection against infection. Consequently, the epidemiologists warn polio could build in Europe for one year, infecting hundreds of people, before the first case of acute flaccid paralysis is detected. People vaccinated with IPV are less likely to transmit polio, but this is only a barrier in areas with high rates of immunization. Some areas fall short in this regard.
In Austria, for example, 83% of people are vaccinated with IPV, but the rate is likely to be much lower in some areas. These undervaccinated clusters are at particular risk. "The worry is that transmission could reach one of these groups and then spread much more readily," University of Tuebingen epidemiologist and co-author of the Lancet letter Martin Eichner told NPR Shots. Eichner thinks Europe needs to go beyond its current recommendation of vaccinating all Syrian refugees entering the region.
The reinstatement of oral polio vaccine (OPV)--which Europe dropped because in rare cases it causes acute flaccid paralysis--is one option. Israel began an OPV campaign after finding poliovirus in sewage, and the United Nations is embarking on a Middle East-wide vaccination campaign. Lebanon has started to vaccinate 750,000 people, but the refugee situation complicates the project. Reuters reports 800,000 refugees are living in 1,600 locations across the country.