Frequently Asked Questions about Poliomyelitis and Polio Vaccine
Is poliomyelitis still a problem in the United States?
The last case of wild poliovirus infection acquired in the United States was in 1979. Except for an occasional importation,
all cases of paralytic poliomyelitis since 1979 have been caused by live oral polio vaccine.
What about polio in other parts of the world?
The last case of wild poliovirus infection in the Western Hemisphere occurred in Peru in 1991. However, thousands of
poliovirus infections still occur in other parts of the world. The majority of cases are now reported from the Indian
subcontinent, Asia, and Africa.
If there is no polio in the Western Hemisphere, why do we still vaccinate against it?
If polio vaccination were stopped in the United States, there would be millions of susceptible children within a year. Since
wild polio infection still occurs in many parts of the world, the virus could be imported and an epidemic could result.
How is polio spread?
Polio is spread by fecal-oral transmission. This means that the virus is spread directly from the stool of an infected person
to the mouth of another person, probably from contaminated hands. Inanimate objects, such as eating utensils, may also
spread the virus. Food and water are believed to play a minor role in the spread of poliovirus.
What is the currently-recommended schedule for polio vaccination in the United States?
As of January, 1997, the Advisory Committee for Immunization Practices (ACIP) recommends two doses of IPV at 2 and 4
months of age, followed by two doses of OPV at 12-18 months and 4-6 years.
Why has the ACIP recommended this change?
Primarily to reduce the risk of vaccine-associated paralytic polio (VAPP) associated with the all-OPV schedule. The risk of
VAPP following OPV is highest with the first dose, so using IPV for the first two doses should have an impact in reducing
VAPP. Although IPV is very effective in producing serologic immunity to polio, it does not produce significant immunity in
the intestine. As a result, persons who receive only IPV may be infected with, and transmit, wild poliovirus, even though they do not develop paralytic disease. OPV does confer local immunity in the gastrointestinal tract. The sequential schedule should
provide the advantages of both vaccines -- no risk of VAPP with the critical first doses, and gastrointestinal protection from
polio infection with the doses of OPV.
Can an all-OPV or all-IPV schedule still be used?
Yes. Both schedules are still acceptable. IPV may be given at 2, 4, and 12-18 months and 4-6 years; and OPV may be given
at 2, 4, 6-18 months and 4-6 years. Parents or providers may choose among the three schedules.
Under what circumstances should a child receive either all IPV or all OPV?
IPV should be used exclusively if the patient, or a household contact of the patient, is immunocompromised. OPV should
be used if the patient has ever had an anaphylactic reaction to a component of IPV (such as neomycin, streptomycin, or
After what age is routine polio vaccine no longer recommended?
In the United States, routine polio vaccination is not recommended for persons 18 years of age and older.
How long is oral polio vaccine virus shed in the stool after the dose?
Up to 6 weeks. Viral shedding in the stool is generally longest following the first dose and is generally shorter with each
How much of a dose of oral polio vaccine can be spit out before the dose needs to be repeated?
There is no definite rule. However, if, in the judgement of the person administering the vaccine, a substantial amount of
vaccine is spit out, regurgitated, or vomited shortly after administration (i.e., within 5-10 minutes), another dose can be
administered at the same visit. If this repeat dose is not retained, neither dose should be counted, and the vaccine should
be re-administered at the next visit.
Can I vaccinate a child with OPV if their parents have never been vaccinated against polio?
ACIP recommends that children should usually receive OPV regardless of the parents vaccination status. The parents
should be educated about the prevention of household transmission of polio vaccine virus, particularly hand washing
after changing diapers. If the child is certain to return, an alternative approach could be to vaccinate the parent or caretaker
with inactivated polio vaccine prior to or concurrent with OPV vaccination of the child.
How often does vaccine-associated polio occur following oral polio vaccine?
Vaccine-associated paralytic polio (VAPP) is rare. From five to ten VAPP cases have been reported annually since live
polio vaccine was licensed in 1963. From 1980 through 1991, 243 million doses of OPV were distributed and 98 total cases
of VAPP were reported, for an overall risk of 1 case of VAPP per 2.5 million doses distributed. But the risk of VAPP varies
by dose of vaccine. Among immunologically normal recipients of OPV during the same 12 year period there were 35 paralytic
cases (an average of about 3 per year), for an overall risk of one VAPP case per 6.9 million OPV doses. However, among first dose recipients, the risk was 1 per 1.6 million doses. The risk for all other doses was one per 32.8 million doses. The reason for this difference by dose is probably because the vaccine virus is able to replicate longer in a completely nonimmune infant, thus increasing the risk of emergence of a mutant virus that may cause paralysis.
Should practitioners be concerned about "provocation polio", as described in Romania in the recent paper by Strebel, et al?
Provocation polio has not been shown to occur in the United States.
Should OPV be given even when a child is mildly ill with watery diarrhea?
In general, yes. The decision whether or not to vaccinate a child with a concurrent illness depends on the severity of the
illness. If the child does not have a significant fever and is not dehydrated, vaccine should be given.
Can empty OPV dispettes be thrown away in the trash can?
Most localities consider containers which held live virus vaccines as infectious waste, and require that they be autoclaved
before disposal. So these containers should be disposed with used needles and syringes.
(From the Centers for Disease Control and Prevention)