We frequently see children (mostly from certain foreign countries) who have received 6 or more doses of polio vaccine, all administered before 4 years of age. How do we handle this when assessing the child’s immunization history?

It is common practice in many developing countries to administer oral polio vaccine (OPV) to children during both routine visits and periodic vaccination campaigns, so a child’s record may indicate more than 4 doses. Some of these doses may not be valid according to the U.S. immunization schedule.

Doses are considered valid if written documentation indicates that doses of polio vaccine were given after 6 weeks of age and the vaccine received was listed as IPV or trivalent OPV (tOPV). A record simply indicating “OPV” also is acceptable if the OPV was administered before April 1, 2016, and it was not noted as being administered during a vaccination campaign.

There specific criteria for OPV documentation because only trivalent polio vaccine doses count as valid for the U.S. polio vaccination schedule. Trivalent OPV ceased to be used globally in April 2016. OPV administered before April 1, 2016, generally was tOPV. However, “OPV” doses recorded as given during a mass vaccination campaign before April 2016 do not count as valid because such campaigns may have used monovalent or bivalent OPV.

If the history is of a complete series of IPV or tOPV in any combination, at least one dose should be administered on or after 4 years of age and at least 6 months after the previous dose. If a complete series cannot be identified that meets these criteria, then the child should receive as many doses of IPV as needed to complete the U.S. recommended schedule.