...the majority of pilgrims originate from medium or low-income countries with marginal surveillance infrastructure and response capabilities; making it more likely that new introductions of poliovirus in those nations may not be promptly detected 6. ...air traffic from most of the 23 GPEI countries is significant (Table 1), affording opportunities for poliovirus importation to the rest of the world. ...there has been a global shortage of IPV and IPV is rarely available in host countries outside of routine immunization programs. ...except for pilgrims from the Democratic Republic of Congo who are required to have received inactivated polio vaccine (IPV), KSA has not mandated the use of IPV for other countries.