Both orally administered, live attenuated polio vaccines (OPV) and inactivated polio vaccines (IPV) for intramuscular (or subcutaneous) injection are widely used internationally. OPV has been the vaccine of choice for controlling poliomyelitis in many countries, and for the global polio eradication initiative, because of the ease of oral administration, its superiority in conferring intestinal immunity, and its low cost. The only, extremely rare, adverse event associated with OPV use is vaccine-associated paralytic poliomyelitis (VAPP), which may occur in vaccine recipients or their contacts. The overall risk of VAPP is estimated at around 1 case per 2.4 million doses administered.
As long as transmission of wild poliovirus has not been interrupted globally, WHO recommends that OPV should remain the vaccine of choice for routine infant immunization in most countries. The primary series of three OPV vaccinations should be administered according to the particular national immunization schedule, for example at 6, 10 and 14 weeks, or 2, 4 and 6 months of age. The interval between doses should be at least 4 weeks. An OPV dose at birth should be added in countries at higher risk of poliovirus importation and spread.
Routine vaccination with IPV alone should be used only in countries with high immunization coverage (> 90%) and at low risk of wild poliovirus importation and spread. A primary series of three IPV doses should be administered, beginning at 2 months of age. If the primary series begins earlier (e.g. with a 6-, 10- and 14-week schedule), a booster dose should be administered after an interval of at least 6 months (four- dose IPV schedule).
Routine vaccination with a sequential schedule using IPV followed by OPV can also be used in countries with low risk of importation and high immunization coverage.
Before travelling to areas where polio cases are still occurring, travellers from polio-free countries should ensure that they have completed the age-appropriate polio vaccine series as recommended by their respective national immunization schedule. Travellers to polio-infected areas who have previously received three or more doses of OPV or IPV should also be given another dose of polio vaccine before departure. Travellers to polio-infected areas who have not received any polio vaccine previously should complete a primary schedule of polio vaccination before departure.
Before travelling abroad, individuals living in areas where polio cases are still occurring should have completed a full course of vaccination against polio, preferrably with OPV, to boost intestinal immunity and reduce the risk of poliovirus shedding, which otherwise may lead to re-introducing of poliovirus into a polio-free area. Travellers from infected areas should receive an additional dose of OPV at least 6 weeks before each international journey.
In case of urgent travel, a minimum of one dose of OPV should be given, ideally 4 weeks before departure. Some polio-free countries (e.g. Saudi Arabia) may require that travellers coming from polioinfected countries or areas be immunized against polio before applying for an entry visa, or that travellers receive an additional dose on arrival, or both.
All travellers are advised to carry the written vaccination record (patient-retained record) in the event that evidence of polio vaccination is requested for entry into countries being visited, preferably using the IHR 2005 International Certificate of Vaccination or Prophylaxis. The certificate is available from the WHO web site at http://www.who.int/ihr/IVC200_06_26.pdf.