Canadian Doctors Urge Vaccination After First US Case of Polio in a Decade

Canadian infection experts are taking note after US officials reported last week that an unvaccinated American was diagnosed with the first case of polio in the country in nearly a decade.

Health Canada hasn’t recorded a case of the virus in more than 25 years, but infectious disease experts say they always have “eyes and ears open for vaccine-preventable diseases like polio” that continue to circulate in other parts of the world.

“Any imported infection is just a flight away,” said Dr. Vinita Dubey, associate medical officer for health at Toronto Public Health.

The polio vaccine is part of the standard set of vaccines for children, but Dubey said some parents are choosing not to vaccinate their children and the COVID-19 pandemic has delayed vaccinating others.

That is creating a renewed risk of vaccine-preventable diseases as people return to international travel after a two-year break, he said. Global polio vaccination efforts were suspended for part of that time, compounding the problem.

A single case of polio triggers a public health response and is reportable under international health standards. By the time a case of paralytic polio is diagnosed, many more people are likely to have been infected.

That is the fear in Rockland County, New York, where a patient was diagnosed with polio after experiencing paralysis. Officials are hosting vaccine clinics and asking health care providers to keep an eye out for more cases.

Poliovirus is highly contagious and usually causes no or mild symptoms, such as low-grade fever, malaise, nausea, diarrhea, and sore throat. The illnesses are most common in infants and young children, but adults who are not fully immunized can also get sick. The virus attacks the nervous system, with one to five percent of infections causing meningitis and less than one percent resulting in paralysis.

Polio cases in Canada fell sharply with the introduction of immunization programs in the 1950s, when up to 5,000 children had polio each year. The last case of wild poliovirus in Canada occurred in 1977, while cases associated with oral vaccines continued until 1995.

Polio infection can occur from the spread of the wild virus or from transmission of the virus after a child receives the oral polio vaccine, which Canada stopped giving in 1996 but is still in use in many other countries.

With the oral vaccine, the virus passes through the body and is excreted in the stool. The virus then spreads easily and infects the next person when it enters the mouth from hands contaminated with feces. The virus can also live in the throat and can be spread through respiratory secretions. People who are immunized can get and spread the virus, but they usually don’t get sick.

Canada’s routine childhood immunization schedules include injectable polio vaccines before age two and a booster between ages four and six. The injectable form of the vaccine is inactivated and does not transmit the virus from person to person.

Wild poliovirus remains endemic in two countries, Afghanistan and Pakistan, but more than 30 countries reported vaccine-associated polio outbreaks in 2020.

With summer travel in full swing, experts said adults and children alike should have their routine vaccinations up to date and check to see if they need additional shots for their destination.

“Vaccine hesitancy is another effect of the pandemic,” said Dr. Valerie Lamarre, an infectious disease pediatrician at St. Justine’s Hospital in Montreal, “It definitely didn’t improve the situation with vaccine-preventable diseases.”

And while the US polio case is not a threat to Canada, Lamarre said that doesn’t mean it should be ignored.

“We are going to see these cases appear from time to time. This just means, ‘Wake up people.’ Get your shots,” he said. “These diseases are preventable.”

This report from The Canadian Press was first published on July 26, 2022.

Michelle Ward is a pediatrician, associate professor, and journalist in Ottawa.

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