Polio Virus Associated With Oral Vaccine Reported In Minnesota Resident
State health officials are investigating a case of infection associated with the polio virus in a Minnesotan who died last month.
The patient was infected with a virus strain found in the oral polio vaccine. The oral vaccine, which is no longer used in the U.S., contained live polio virus. The injected polio vaccine now in use contains only inactivated virus.
The patient died with symptoms that included paralytic polio, but it is not known to what extent the polio may have contributed to the death. The patient had a weakened immune system and multiple health problems. The patient most likely acquired the vaccine-derived polio virus from someone who had received the live-virus, oral poliovirus vaccine (OPV) before the use of OPV was discontinued nine years ago.
Infection from polio virus can cause a wide range of symptoms. Most infections result in no or mild symptoms, but in rare cases can severely affect the neurologic system, resulting in paralysis.
Minnesota Department of Health officials are emphasizing that there is no risk to the general public from this case. Only people who have had direct, close contact with the patient, such as certain health care workers, may be at risk of infection. Adhering to recommended infection control guidelines and being vaccinated protect against polio. At this time, no additional cases of infection with the polio virus have been reported in connection with the patient.
"We are working closely with our local and national partners to investigate this case," said Minnesota State Epidemiologist Dr. Ruth Lynfield. "It's important to note that while there is no risk to the general public, many people still have vivid memories of a time when polio was a major public health concern before the first vaccines were introduced in the 1950s. This is a very rare occurrence and does not signal a resurgence of polio."
MDH staff are working with hospital staff to determine if there might be health care workers at risk for disease. Hospital staff are notifying all health care workers who may have been exposed. "Only unvaccinated people or people with deficient immune systems who have had direct, ungloved contact with the patient's bodily secretions are at any risk for disease," said Dr. Aaron DeVries, Medical Epidemiologist at MDH. Health officials will follow up with health care workers to make sure their immunizations are up to date and they are showing no signs of disease. "If you don't hear from a public health or health care official, you're not at risk," DeVries said.
This type of polio infection is very rare, officials stressed. In rare instances, a person who has either never been vaccinated or has certain immunodeficiencies can acquire the polio virus from someone who has been vaccinated and is excreting the virus in their stool. Sometimes these infections result in illness, as happened in this situation. Only 45 cases of vaccine-derived polio disease in persons with immunodeficiencies have been reported in the world since 1961.
This is the second instance of a polio infection caused by a vaccine strain of virus in the United States since 2000, when use of live-virus oral polio vaccine was discontinued in the U.S. All polio vaccinations in the U.S. are now done with an injected, killed-virus vaccine. The other instance of vaccine-derived polio infection also occurred in Minnesota, in 2005, but was very different from this case. It occurred in an unimmunized child from a community that had high levels of non-immunization and that case was not associated with neurological symptoms.
"We suspect that one reason why Minnesota has detected both cases in the United States in the last 10 years is because of the high level of cooperation among astute clinicians, a network of clinical laboratories and the Minnesota Department of Health, which in turn has a Public Health Laboratory that looks for such rare agents as polio virus," Lynfield said.
Naturally-occurring polio has been eradicated in the western hemisphere. The last case of naturally-occurring (not from vaccine) paralytic polio disease occurred in the United States in 1979.
Although members of the general public are not at risk, MDH officials say this unusual case should serve as a reminder to make sure that all of your immunizations are current and that children receive immunizations as recommended.
"It's always a good idea to check with your physicians or health care providers to be certain all of your vaccinations are current," DeVries said. "Make sure you're protected and your children are protected."
Most people in the United States have been vaccinated against polio and healthy people have developed full immunity to the disease. An estimated 94 percent of Minnesota's two-year-olds have had the full primary series of three polio shots, which are usually administered in infancy.