Is Polio Re-Emerging? What Travellers Should Know
Polio has been in the news lately as there was a case of vaccine-derived polio in July 2022 in the US. The case occurred Rockland County, New York in an unvaccinated resident. Vaccine-derived poliovirus has also been detected in environmental samples in Rockland County and neighbouring Orange County, New York as well as in London, UK. Both strains have been genetically linked to environmental samples in Israel. What does this mean? Is polio re-emerging? Are you at risk? Did you know that proof of polio vaccination is required for travel to certain countries? Keep reading to find out everything you need to know about polio.
What is polio?
Poliomyelitis, or polio, is spread by 3 types of polio viruses found in food and water contaminated by the feces of an infected person. It is a highly infectious disease that can invade the nervous system and cause paralysis and difficulty breathing. Symptoms of polio can range from asymptomatic to severe symptoms including acute flaccid paralysis, respiratory failure, and rarely death.
Polio vaccines in Canada
There are two types of polio vaccines, the Inactivated Polio Vaccine (IPV) and the live, oral polio vaccine (OPV). The polio vaccine was introduced into BC’s routine vaccine schedule in 1959 for children and adults. Over the years a combination of OPV and IPV have been used. The OPV was discontinued in Canada in 1994. Today, infants receive IPV in combination with other routine vaccines at 2, 4, 6, and 18 months of age, with a fifth dose between 4-6 years of age. An adult booster of polio vaccine is only recommended for health care workers who may be exposed to feces, or for travel to certain countries.
The goal for polio eradication
Prior to the introduction of the polio vaccine, wild poliovirus (WPV) was common worldwide. The Global Polio Eradication Initiative was initiated in 1988 and has succeeded in significantly decreasing the number of countries where WPV is a risk. WPV now remains endemic in only two countries: Afghanistan and Pakistan. There has been a recent case of WPV in Malawi and another in Mozambique, showing that international spread of the disease remains a possibility until the world is free of WPV.
The return of polio in polio-free countries
A decrease in immunization rates is to blame for the return of polio. Countries with extremely low immunization rates have seen cases of vaccine-derived polioviruses. Many countries worldwide vaccinate with OPV, which is a live, weakened vaccine that replicates in the intestines to produce antibodies and is then excreted in the feces. If a population is extremely under-immunized, the excreted vaccine virus can continue to circulate for extended periods of time, which allows time for the virus to undergo genetic changes into a form that can cause disease. The excreted vaccine virus would need to be allowed circulation for at least 12 months for vaccine-derived polioviruses to occur, which would only be possible among populations with extremely low immunization rates.
In Rockland County and neighbouring Orange County, US, where environmental samples of polio have been detected, polio vaccination rates are 60% and 59% respectively. These low immunization rates have enabled vaccine-derived polioviruses to circulate in these areas. It is likely that the initial spread of polio in the environmental samples began from a person who had been vaccinated outside of the US with OPV, which has been discontinued in the US.As reported by CBC news, areas in London, UK where polio has been detected in environmental samples, have some of the lowest vaccination rates in the country. Vaccination campaigns are ongoing in these areas of the US and UK.
The risk of vaccine-derived polioviruses occurring is extremely low, and the benefits of using OPV far outweigh the risks. Since 2000 more than 10 billion doses of OPV have been administered worldwide to nearly 3 billion children, resulting in 13 million cases of polio being prevented and reducing the disease by 99%.
Risk to travellers
The risk of polio to travellers is very low. Even completely unvaccinated travellers going to a country where polio is circulating have almost no risk of acquiring clinical polio.
Before travelling to areas where there is wild poliovirus or vaccine-derived poliovirus, travellers should ensure they have completed their primary polio vaccine series, which should typically have been completed as a child. Unvaccinated adults beginning the primary series should have 3 doses of the polio vaccine at 0, 1, and 6 months. Depending on a person’s destination, adults who have completed the primary series may be recommended to receive an additional booster dose, which then provides lifetime protection against polio.
Travel to the US and UK
The risk of polio for travellers to the US and UK is negligible. A booster dose of the polio vaccine is not recommended for those who have completed a primary series of polio. The polio vaccine has been included in the primary series in BC since 1959. Those who have not completed a primary series of the polio vaccine should contact Public Health.
Polio vaccination requirements
Proof of recent polio vaccination may be required when travelling to polio-affected countries. In 2014 the World Health Organization (WHO) declared the international spread of polio to be a public health emergency and issued temporary polio vaccine recommendations for travellers. Long-term travellers (staying >4 weeks) and residents may be required to show proof of polio vaccination when departing from polio-affected countries. The polio vaccine should be given between 4 weeks and 12 months before departure from the polio-affected country and documented on an International Certificate of Vaccine or Prophylaxis.
Visit a travel clinic!
Country requirements for proof of polio vaccination are often changing. The experts at TravelSafe Clinic are up to date on polio outbreaks, current recommendations and requirements for polio vaccination. Book your consultation at TravelSafe Clinic to determine if you need the polio vaccine for your trip, and to receive your International Certificate of Vaccine or Prophylaxis.