Description

Poliomyelitis is an acute viral infection that involves the gastrointestinal tract and occasionally the central nervous system. It is acquired by fecal-oral or oral transmission (1).

Occurrence

In the pre-vaccine era, infection with poliovirus was common worldwide, with epidemics occurring in the summer and fall in temperate areas (1). The incidence of poliomyelitis in the United States declined rapidly after the licensure of inactivated polio vaccine (IPV) in 1955 and live oral polio vaccine (OPV) in the 1960s. The last cases of indigenously acquired polio in the United States occurred in 1979 (2). The global polio eradication program subsequently led to elimination of polio in the Americas, where the last wild virus-associated polio case was detected in 1991 (3). In 1999, a change in vaccination policy in the United States from use of OPV to exclusive use of IPV resulted in the elimination of 8-10 vaccine-associated paralytic poliomyelitis (VAPP) cases that had occurred annually since the introduction of OPV in the 1960s (4).

Two recent events in the United States, however, highlight the continuing but low risk of OPV exposure for unvaccinated persons. In 2005, a case of imported VAPP occurred in an unvaccinated U.S. adult who had traveled abroad, likely from contact with an infant recently vaccinated with OPV (5). Similarly, in 2005, an unvaccinated immunocompromised infant and four children in two other families in the same small rural community were found to be asymptomatically infected with a vaccine-derived poliovirus, presumably originating outside the United States in a country that uses OPV (6).

Globally, clusters of cases and small outbreaks of vaccine-derived polioviruses have occurred since 2000, including ones in the Dominican Republic and Haiti (2000-2001), the Philippines (2001), Madagascar (2002 and 2005), China (2004), Indonesia (2005), and Cambodia (2005-2006) (7-8). More significantly, during 2002-2006, a total of 22 previously polio-free countries were affected by importations of wild poliovirus (WPV) type 1 from the remaining polio-endemic countries, primarily Nigeria (9-10). In spite of these recent outbreaks, the global polio eradication initiative has reduced the number of reported polio cases worldwide by more than 99% since the mid-1980s, and worldwide eradication of the disease appears feasible in the future (10-11).

Risk for Travelers

Because of polio eradication efforts, the number of countries where travelers are at risk for polio has decreased dramatically. Most of the world’s population resides in areas considered free of wild poliovirus circulation at the time of publication, including the Western Hemisphere, the Western Pacific Region (which encompasses China), and the European region. Vaccination is recommended for all travelers to polio-endemic or epidemic areas. As of November 2006, these areas include Africa, South Asia, Southeast Asia, and the Middle East. For current information on the status of polio eradication efforts and vaccine recommendations consult the Travel Notices at http://wwwn.cdc.gov/travel/ or the Global Polio Eradication Initiative (http://www.polioeradication.org/). Polio vaccine is not typically required by law; however, there are polio vaccine requirements for attending the annual Hajj in Saudi Arabia.

Clinical Description

Clinical manifestations of poliovirus infection range from asymptomatic (most infections) to symptomatic, including acute flaccid paralysis of a single limb to quadriplegia, respiratory failure, and, rarely, death (1).

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), three doses of live oral poliovirus (OPV), or four doses of any combination of IPV and OPV. To eliminate the risk of vaccine-associated paralytic poliomyelitis, OPV has not been recommended for routine immunization in the United States since January 1, 2000, and is no longer available in this country (12). OPV continues to be used in the majority of countries and for global polio eradication activities (10-11).

VACCINE

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 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 (12).

Adults

Adults who are traveling to areas where poliomyelitis cases are still occurring and who are unvaccinated, incompletely vaccinated, 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 (12). 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 intervals recommended above, if the person remains at increased risk for poliovirus exposure (12). Adults who are traveling to areas where poliomyelitis cases are occurring and who have received a primary series with either IPV or OPV should receive another dose of IPV before departure. For adults, available data do not indicate the need for more than a single lifetime booster dose with IPV (12).

Allergy to Vaccine

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 (12).

Pregnancy and Breastfeeding

If a pregnant woman is unvaccinated or incompletely vaccinated and requires immediate protection against polio because of planned travel to a country or area where polio cases are occurring, IPV can be administered as recommended in the adult schedule (12). Breastfeeding is not a contraindication to immunization of an infant or mother against polio (12).

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 (12).

Immunosuppression

IPV may be administered safely to immunodeficient travelers and their household contacts. Although a protective immune response cannot be ensured, IPV might confer some protection to the immunodeficient person (12). Persons with certain primary immunodeficiency diseases should avoid contact with excreted OPV virus (e.g., exposure to a child vaccinated with OPV within the previous 6 weeks); however, this situation no longer occurs in the United States unless a child receives OPV overseas.

References

1. CDC. Poliomyelitis. In: Atkinson W, Hamborsky J, McIntyre L, Wolfe S, eds. Epidemiology and prevention of vaccine-preventable diseases. 9th ed. Washington, DC: Public Health Foundation; 2006. p. 97-110.
2. CDC. Poliomyelitis — United States, 1975-1984. MMWR Morbid Mortal Wkly Rep. 1986;35:180-2.
3. CDC. International Notes: Certification of poliomyelitis eradication — the Americas, 1994. MMWR Morbid Mortal Wkly Rep. 1994;43:720-2.
4. Alexander LN, Seward JF, Santibanez TA, et al. Vaccine policy changes and epidemiology of polio in the United States. JAMA. 2004;292:1696-701.
5. CDC. Imported vaccine-associated paralytic poliomyelitis — United States, 2005. MMWR Morbid Mortal Wkly Rep. 2006;55;97-9.  
6. CDC. Poliovirus infections in four unvaccinated children — Minnesota, August–October, 2005. MMWR Morbid Mortal Wkly Rep. 2005;54;1053-5.
7. Kew OM, Sutter RW, de Gourville EM, Dowdle WR, Pallansch MA. Vaccine-derived polioviruses and the endgame strategy for global polio eradication. Annu Rev Microbiol. 2005:59;587-635.
8. CDC. Update on vaccine-derived polioviruses. MMWR Morbid Mortal Wkly Rep. 2006;55:1093-7.
9. CDC. Resurgence of wild poliovirus type 1 transmission and consequences of importations — 21 countries, 2002–2005. MMWR Morbid Mortal Wkly Rep. 2006;55:145-50.
10. CDC. Progress toward interruption of wild poliovirus transmission— Worldwide, January 2005–March 2006. MMWR Morbid Mortal Wkly Rep. 2006;55:458-62.
11. World Health Organization. Conclusions and recommendations of the Advisory Committee on Poliomyelitis Eradication, Geneva 11–12 October 2005. Wkly Epidemiol Rec. 2005;80;410-6.
12. CDC. Poliomyelitis prevention in the United States — updated recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morbid Mortal Wkly Rep. 2000;49(RR-5):1-22.

JAMES P. ALEXANDER, MARGARET WATKINS