POLIO (Poliomyelitis)
Epidemiology and transmission
Although vaccination has almost eliminated poliomyelitis in western Europe, Canada , the United States , Australia , Japan, and New Zealand , the disease is still extant in developing countries.
Approximately 250,000 cases occur each year. Progress has been made in reducing disease in Central and South America where only 130 confirmed cases occurred in 1989, 18 in 1990, and 9 in 1991. Transmission is fecal-oral. A recent outbreak in Israel was linked to waning immunity in adults who had received the inactivated vaccine in childhood. Outbreaks are occasionally reported from religious groups who abstain from vaccination.

Etiology

Polioviruses belong to the Enterovirus genus and contain RNA.


Clinical presentation
Most persons are asymptomatic. Between 0.1% and 2% of patients will have clinically apparent disease. About 0.1% of all persons who acquire the virus have myalgias followed by asymmetric, flaccid paralysis. Involvement of the cranial nerves may cause bulbar paralysis. Case fatality rates as high as 5% result from respiratory failure.

Preparing the international traveler

The Centers for Disease Control and Prevention recommend that all travelers to developing countries be fully immunized against poliomyelitis.

Two vaccine products are available. The first is the trivalent oral polio vaccine (OPV). This is a live vaccine and is the primary vaccine used in children under the age of 18. The risk of acquiring paralytic polio from the vaccine is one in several million. Because of the fecal-oral transmission, persons who receive OPV should be cautioned to wash their hands after using the bathroom to avoid transmission of the vaccine strain to others.

The enhanced potency inactivated polio vaccine (IPV) is used for adults who have never been vaccinated before (primary vaccination), because it does not have a potential to case paralytic disease. It is also the vaccine of choice in immunocompromised individuals and their caretakers.

Persons who have received the primary vaccine series in the past should receive a single booster if more than 10 years has elapsed since their last immunization. The booster may be either OPV or IPV.


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 to 18 months of age, and 4 to 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).