Poliomyelitis aka polio is a highly infectious disease that infects the nervous system often causing paralysis and even death. Polio affects children under the age of 5 who have not been fully vaccinated through the fecal oral route. There are currently 3 types of polio virus: including type 1, type 2, and type 3. Although there is no cure for the disease, large efforts have been underway to eradicate this disease.
Polio which has plagued the world is now at an all time low with only 33 cases reported in 2018. In fact, efforts to combat this disease has resulted in a 99.9% decrease in cases since 1988. Since eradication efforts began, the disease has been eliminated in more than 120 countries; however, the stubborn disease still remains endemic in three countries. Eradication efforts began 30 years ago, and currently there is a global push for complete eradication of polio by 2023. In fact, the U.S. government plays a huge role in this effort by providing funding of more than $235 million dollars in 2018.
So what interventions have been so successful at eliminating this disease? Several strategies have been used in order to prevent the spread of polio. Ensuring greater than 80% of routine immunization of infants under the age of one by giving at least three doses of oral poliovirus vaccine (OPV) has proven very effective in reducing the number of polio cases. Along with the OPV, inactivated Polio Vaccine IPV is also another vaccine that prevents the disease. Mass immunization campaigns and heightened polio surveillance to detect any new cases and targeted campaigns also called “mop-up” campaigns to respond to any possible outbreaks in specific areas are also interventions currently taking place to battle polio. Mass immunization in conjunction with routine immunity allows communities to build herd immunity and plays an important role in protecting those who have not been immunized or may only be partially immunized. In order for herd immunity to be effective in eliminating the disease, high levels of immunization must be sustained. During campaigns, volunteers vaccinate thousands, even millions of children. Secondary efforts include the support from health care workers, communication campaigns, community engagement, and new scientific and technological advances.
Although OPV is easily administered and the still the main preventative to vaccinate children, eventually a switch to inactivated poliovirus vaccine (IPV) will be phased in over the next several years. This allows for prevention of outbreaks that are caused by circulating vaccine-derived polioviruses since OPV contains attenuated virus. IPV which is given intravenously and requires a trained health care worker targets all three types of wild poliovirus whereas OPV only protects against two wildtype. IPV is used in conjuction with OPV to strengthen the immune system in many countries.
Although the vaccine is relatively cheap, efforts to vaccinate the most at risk population still serves as a challenge because these endemic regions are often geographically isolated or struggle with extreme poverty or conflict. These factors make it hard for health care workers to access these areas. For example, a recent attack on health care workers involved in vaccinating for polio in Pakistan highlighted concerns that may hamper progress for complete eradication.
Each country has its own specific immunization schedule. Some countries use only OPV or IPV alone whereas others use a combination. Although OPV is very effective, it can in very rare cases cause paralysis known as vaccine associated paralytic poliomyelitis (VAPP). In order to combat this rare disease, starting in 2016 there was a campaign for all countries to include at least one dose of IPV. IPV has proven very safe and effective in humans whether used alone or alongside OPV and no serious adverse affects have been reported thus far. IPV has been used in the US since 2000 in order to eliminate the possible risk of contracting circulating poliomyelitis or VAPP.
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