Diseases > Polio
What is Polio?
is an infectious disease caused by a virus that
lives in the throat and intestinal tract. It
is spread through person-to-person contact with
the stool of an infected person (for instance,
by changing diapers). Polio used to be very
common in the U.S. and caused severe illness
in thousands of people each year before polio
vaccine was introduced in 1955.
people infected with the polio virus have no symptoms
but some infections cause paralysis and even death.
are the symptoms of polio?
Up to about 95 percent of people infected with polio have
no symptoms. However, infected persons without symptoms
can still spread the virus and cause others to develop polio.
About four to eight percent of infected persons have minor
symptoms such as fever, sore throat, upset stomach, or flu-like
symptoms and have no paralysis or other serious symptoms.
About one to two percent of infected persons develop aseptic
meningitis with stiffness of the back, back or legs, and
in some persons increased or abnormal sensations. Symptoms
typically last from two to ten days, followed by complete
recovery. Less than 1 percent of polio cases result in paralysis.
The risk of paralysis increases with age.
common was polio in the United States?
was one of the most dreaded childhood diseases
of the 20th Century in the United States.
There were usually about 13,000 to 20,000
cases of paralytic polio reported each year
in the US before the introduction of Salk
polio vaccine in 1955. Polio peaked in 1952
when there were more than 21,000 reported
cases. The number of cases of polio decreased
dramatically following introduction of the vaccine
and the development of a national vaccination
program. In 1965, only 61 cases of paralytic
polio were reported compared to 2,525 cases
reported cases just five years earlier in 1960.
polio still a disease seen in the United
The last cases of naturally occurring paralytic polio in
the United States were in 1979, when an outbreak occurred
among the Amish in several Midwestern states. From 1980
through 1999, there were 152 confirmed cases of paralytic
polio cases reported. Of the 152 cases, eight cases were
acquired outside the United States and imported. The last
imported case caused by wild poliovirus into the Untied
States was reported in 1993. The remaining 144 cases were
vaccine-associated paralytic polio (VAPP) caused by live
oral polio vaccine.
kind of polio vaccines are used in the United
one kind of polio vaccine, IPV, which is
given as a shot, is now used in the United
States. A live, oral polio vaccine
(OPV) has not been used in the United States
since 2000 but is still used in many parts
of the world.
is a vaccine-derived poliovirus?
vaccine-derived poliovirus (VDPV) is a strain
of polio virus, initially contained in the live
OPV, that has changed over time and behaves more
like a wild or naturally-occurring virus. This
means it can be more easily spread to others who
are unvaccinated against polio and who come in
contact with the stool or oral secretions (e.g.
saliva) of an infected person. These viruses may
cause illness, including paralytic poliomyelitis.
there a difference in a disease caused by a
VPDV and one cause by wild poliovirus or OPV?
there is no clinical difference between paralytic
polio caused by wild poliovirus, OPV or a VDPV.
heard that a child has been found with VDPV.
Is this true?
2005, a VDPV was found in the stool of an unvaccinated
child in the state of Minnesota. The child most
likely caught the virus through contact in the
community with someone who received live oral
vaccine in another country. For questions
specifically related to this case visit http://www.health.state.mn.us/news/pressrel/polio100105.html.
do vaccine-derived polioviruses come from?
OPV has not been used in the United States since
2000, it is likely that any vaccine-derived poliovirus
(VDPV) seen in the United States would have come
from a person who received OPV in another country.
OPV is used in many countries of the world, including
Central and South America, Africa, and Asia.
Should I be concerned if there is a case of VDPV in the United States?
vaccination can protect people against naturally
occurring polioviruses and vaccine-derived polioviruses.
It is unlikely that a VDPV would become widespread
because most people in the United States have been
vaccinated against polio. Most VDPVs disappear
over time without causing any clinical disease.
Very rarely, usually in communities where routine
polio immunization has been low, VDPVs have spread
beyond close contacts. Over the past decade, more
than ten billion doses of OPV have been given worldwide,
with only 6 outbreaks of circulating VDPVs confirmed,
resulting in only approximately 50 cases of paralytic
polio. Persons who are not up to date with polio
immunizations should talk with their healthcare
should get polio vaccine and when?
vaccine or IPV is a shot, given in the leg or arm,
depending on age. Polio vaccine may be given at
the same time as other vaccines.
people should get polio vaccine when they are children.
Children get 4 doses of IPV, at these ages:
dose at 2 months
- A dose at 4 months
- A dose at 6-18 months
- A booster dose at 4-6 years
adults do not need polio vaccine because they were
vaccinated as children. But, in general, three
groups of adults are at higher risk for coming
into contact with polio virus and should consider
traveling to areas of the world where polio
- laboratory workers who might handle polio virus,
- health care workers treating patients who could
in these three groups as well as those in communities
where VPDV has been isolated who have never been
vaccinated against polio should get 3 doses of
first dose at any time,
- The second dose 1 to 2 months later,
- The third dose 6 to 12 months after the second.
accelerated vaccination schedule can be used for
unvaccinated children and adults with 4 week intervals
between the 3 doses of the primary series.
at high risk of coming in contact with polio virus
who have received the 3 dose primary series should receive
a booster dose of IPV. Based on available information, adults
do not need more than a single lifetime booster dose with
your health care provider for more information.
Recommendations for polio vaccine in the United
States are available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr4905a1.htm or http://www.cdc.gov/mmwr/PDF/rr/rr4905.pdf.
many children are vaccinated against polio
in the United States?
to the 2004 National Immunization Survey conducted
by the Centers for Disease Control and Prevention
(CDC), about 92 percent of children aged 19 to
35 months living in the United States were vaccinated
against polio. About 95.5 percent of US children
are vaccinated against polio before school entry.