Poliomyelitis

Description

Poliomyelitis is an acute infection that involves the gastrointestinal tract and, occasionally, the central nervous system. It is acquired by fecal-oral transmission.

Occurrence

In the prevaccine era, infection with poliovirus was common, with epidemics occurring in the summer and fall in temperate areas. The incidence of poliomyelitis declined rapidly after the licensure of inactivated polio vaccine in 1955 and oral polio vaccine in the 1960s. The last cases of indigenously acquired polio in the United States occurred in 1979. Although a polio eradication program led to elimination of polio in the Western Hemisphere, where the last case associated with wild poliovirus was detected in 1991, outbreaks of vaccine-derived poliovirus type 1 occurred in the Dominican Republic and Haiti in July 2000 and in the Philippines in 2001. In spite of these recent outbreaks, the global polio eradication initiative has reduced the number of reported polio cases worldwide by >99% since the mid-1980s, and worldwide eradication of the disease appears feasible in the near future.

Risk for Travelers

Travelers to countries where polio is epidemic or still endemic should be fully immunized. Because of polio eradication efforts, the number of countries where travelers are at risk for polio has decreased dramatically. Concurrent with the decline in polio incidence, the number of polio-endemic countries decreased from >120 in 1988 to approximately 10 in 2001. Most of the world's population resides in areas now considered free of wild poliovirus circulation, including the Western Hemisphere, the Western Pacific Region (which encompasses China), and the European region. Most of the world's remaining poliovirus transmission is in five countries: Afghanistan, India, Pakistan, Nigeria, and Niger.

Clinical Description

Clinical manifestations of poliovirus infection range from asymptomatic (the majority of infections) to symptomatic, including acute flaccid paralysis of a single limb to quadriplegia, respiratory failure, and, rarely, death.

Prevention

A person is considered to be fully immunized if he or she has received a primary series of at least three doses of inactivated poliovirus vaccine (IPV), live oral poliovirus (OPV), or four doses of any combination of IPV and OPV. To eliminate the risk of vaccine-associated paralytic poliomyelitis, OPV is no longer recommended for routine immunization in the United States as of January 1, 2000. OPV is no longer available in this country, although it continues to be used for global polio eradication activities.

Infants and Children

Because OPV is no longer recommended for routine immunization in the United States, all infants and children should receive four doses of IPV at 2, 4, and 6–18 months of age, and 4–6 years of age. If accelerated protection is needed, the minimum interval between doses is 4 weeks, although the preferred interval between the second and third doses is 2 months. The minimum age for IPV administration is 6 weeks. Infants and children who have initiated the poliovirus vaccination series with one or more doses of OPV should receive IPV to complete the series.

Adults

Adults who are traveling to polio-endemic areas and are unvaccinated or whose vaccination status is unknown should receive IPV. Two doses of IPV should be administered at intervals of 4–8 weeks; a third dose should be administered 6–12 months after the second. If three doses of IPV cannot be administered within the recommended intervals before protection is needed, the following alternatives are recommended:

• If >8 weeks is available before protection is needed, three doses of IPV should be administered at least 4 weeks apart.
• If <8 weeks but >4 weeks is available before protection is needed, two doses of IPV should be administered at least 4 weeks apart.
• If <4 weeks is available before protection is needed, a single dose of IPV is recommended.

The remaining doses of vaccine should be administered later, at the recommended intervals, if the person remains at increased risk for poliovirus exposure. Adults who are traveling to polio-endemic areas and have received a primary series with either IPV or OPV can receive another dose of IPV. For adults, available data do not indicate the need for more than a single lifetime booster dose with IPV.

Adverse Reactions

Allergy. Minor local reactions (pain and redness) can occur following IPV. No serious adverse reactions to IPV have been documented.

IPV should not be administered to persons who have experienced a severe allergic (anaphylactic) reaction after a previous dose of IPV or to streptomycin, polymyxin B, or neomycin. Because IPV contains trace amounts of these three antibiotics, hypersensitivity reactions can occur among persons sensitive to them.

Pregnancy. Although no adverse events of IPV have been documented among pregnant women or their fetuses, vaccination of pregnant women should be avoided on theoretical grounds. However, if a pregnant woman is unvaccinated and requires immediate protection against polio, IPV can be administered as recommended in the adult schedule. Breast-feeding is not a contraindication to immunization against polio.

Precautions and Contraindications

IPV may be administered to persons with diarrhea. Minor upper respiratory illnesses with or without fever; mild to moderate local reactions to a previous dose of IPV; current antimicrobial therapy; and the convalescent phase of acute illness are not contraindications for vaccination.

Immunosuppression. Administration of IPV to immunodeficient travelers is safe, and IPV is the only polio vaccine recommended for use in immunodeficient travelers and their household contacts. Although a protective immune response cannot be ensured, IPV might confer some protection to the immunodeficient person. Persons with certain primary immunodeficiencies should avoid contact with excreted polio vaccine virus (e.g., as may occur with a child vaccinated with OPV within the previous 6 weeks).

— Lorraine Alexander, Trudy Murphy