ATLANTA - In what has been called "a historic moment," the Advisory Committee on Immunization Practices (ACIP) recently recommended that oral polio vaccine (OPV) no longer be used for routine immunization against polio. The ACIP recommended inactived poliovirus vaccine (IPV) be used for the entire four-dose series.
The change to the U.S. childhood immunization schedule is aimed at eliminating the small chance of vaccine-associated paralytic polio (VAPP), which can occur with the administration of OPV, a live-virus vaccine. Until recently, there were about six to eight cases of VAPP each year, which meant that for every 2.3 million doses of OPV, one person contracted polio due to the vaccine. Since there is no more wild poliovirus in this country, the ACIP deemed that this risk, although small, was no longer acceptable. The committee vote was 8 in favor of a change to four doses of IPV, with 1 abstaining and 3 absent.
The ACIP has been working incrementally toward this change. Two years ago, the committee recommended a sequential schedule of two doses of IPV followed by two doses of OPV. This change has already reduced the number of VAPP cases from a handful to only one reported case last year, according to the Centers for Disease Control and Prevention (CDC).
Opposition to the changes took two forms: concern over the increased number of injections a child must receive to be fully immunized and concern that the change will negatively affect the campaign to eradicate polio.
An all IPV vaccine will add four more injections to the immunization schedule, but this is expected to decrease with the introduction of combination vaccines that will contain IPV.
As to the second point, the recommended change to an all IPV schedule will be implemented in the United States only; polio endemic countries will continue to administer OPV vaccine.
"It is a historical moment," said Paul A. Offit, MD, chief of infectious diseases at Children's Hospital in Philadelphia, and head of the ACIP working committee that recommended the change.
The recommendation will take effect as of Jan. 1, 2000. "All children will need to receive four doses of IPV at 2, 4, 6-18 months and 4-6 years of age.
OPV is acceptable only for the following special circumstances: mass immunization campaigns to control outbreaks due to wild-type poliovirus; unimmunized children whose travel to polio-endemic areas is immanent (i.e., less than 4 weeks) may receive OPV for only the first dose; children of parents who do not accept the recommended number of vaccine injections may receive OPV only for dose three or four or both," said the draft recommendation. "OPV should be administered only after discussion of the risks of vaccine-associated paralytic polio."
This recommendation will be published as a Notice to Readers in Morbidity and Mortality Weekly Report.
ACIP liaison members from the American Academy of Pediatrics and the American Academy of Family Physicians voiced no opposition with the language adopted by the ACIP, but Offit suggested that there may be slight revisions before the harmonized schedule is released in January 2000. "I have little doubt this will be the final language," Offit said.
Pasteur Mérieux Connaught (PMC) USA, the sole marketer of IPV in the United States, has ample supply of the vaccine to meet the new ACIP implementation guidelines, company officials said. "Pasteur Mérieux Connaught will work with government health officials and medical organizations to ease the implementation of this new policy. It is great news for parents, children and physicians alike as we realize the hopes of earlier generations for a polio-free nation," said. David J. Williams, president and chief operating officer of PMC.
IPV can be administered by intramuscular or subcutaneous injection. Under the new ACIP recommendations, IPV should be administered to U.S. children for all four doses of polio vaccine (administered at 2 months, 4 months, 6-18 months, and 4-6 years of age) to complete the immunization schedule. Use of OPV is reserved for special circumstances.
An extensive story about the change in the recommended schedule, as well as a history of polio vaccination, will appear in next month's issue of Infectious Diseases in Children when we feature a special section "Hot Shots - Vaccine and Vaccine Developments."
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