Finland: Polio virus detected in wastewater in the Tampere region
The National Institute for Health and Welfare (THL) has found poliovirus in wastewater monitoring in the Tampere region. The discovery turned out to be a mutated poliovirus type 2 (VDPV2). VDPV2 has mutated from the live, weakened, oral polio vaccine virus.
The detection of mutated poliovirus type 2 means that one or more people who shed poliovirus have been in the area during the sampling period. If a fully or partially unvaccinated person encounters the virus, they can become infected and, in rare cases, develop symptomatic polio.
"The discovery is rare, but not completely unexpected. A similar discovery of mutated poliovirus in wastewater was made in Finland about ten years ago. The risk of a polio epidemic in Finland is low. We have one of the best polio surveillance systems in Europe, and in addition, vaccination coverage against polio is high," says Leif Lakoma, Chief Physician at THL .
Polio is being monitored in wastewater in several European countries. Mutated type 2 polioviruses have also been found in wastewater monitoring in Spain, Poland and Germany this autumn. Studies by the World Health Organization (WHO) revealed that the viruses are genetically related to a strain originally detected in Nigeria, which is still circulating in several African countries. However, no polio cases have been detected in Europe.
Vaccines containing live poliovirus are not used in Finland
Polio vaccinations began in Finland in 1957, and Finns are well protected against polio. The last case of polio was detected in Finland in 1985. In the same year, the entire population was offered a polio booster vaccine.
Currently, Finland uses an injectable polio vaccine, which does not contain live viruses, so it cannot cause poliovirus infection. The vaccine is available free of charge as part of the national vaccination program.
Polio vaccination coverage among children is over 98 percent. The vaccine is offered to children at three, five and 12 months of age, with a booster dose at age 4. Adults should ensure that they have received a total of three doses of polio vaccine in their lifetime.
"It is worth ensuring that your close circle of friends and family members are up to date with their vaccinations and, if necessary, taking any missing vaccines. This particularly applies to adults who have come to Finland from abroad to work or study, and whose childhood vaccination coverage may be lacking," says Hanna Nohynek , Chief Physician at THL .
In addition, a booster vaccination is recommended for travelers if their stay in a country with an increased risk of polio infection lasts more than four weeks and it has been more than 12 months since the previous booster dose.
Eradicating polio from the world requires action
The WHO has classified polio as an international public health emergency since 2014. In Finland, polio is classified as a public health emergency.
It is easily transmitted through the digestive tract, either through contact, contaminated surfaces or food, and sometimes, less commonly, through respiratory droplets. In a small proportion of infected people, the virus spreads from the intestines to the central nervous system, causing paralysis of voluntary muscles and later atrophy.
Indigenous polio was eradicated from Europe over 20 years ago. However, isolated live polio vaccine virus strains are found in wastewater monitoring in Finland every year. These unmodified virus strains, which originate directly from vaccines, do not pose a significant risk of further infection. Isolated cases of polio caused by the modified vaccine virus have been detected, for example, in Ukraine in 2021 and in Israel in 2023.
The injectable polio vaccine effectively protects against central nervous system damage caused by polio and its consequences. However, the oral polio vaccine, which contains a live virus, is still used worldwide. Mutated type 2 polioviruses derived from the live polio vaccine have caused more polio cases worldwide than the so-called wild poliovirus for several years.
According to the WHO European Office, the polio discoveries in Europe are a reminder once again of the importance and urgency of eradicating all forms of the polio virus.
The WHO is currently working on a new plan to eradicate polio. The goal is to phase out the live polio vaccine, even though it offers better mucosal protection against polio infection than the injectable vaccine, which does not contain live virus.