SEATTLE — The polio eradication effort has seen huge progress over the last few decades. According to the World Health Organization (WHO), polio cases have decreased by more than 99 percent since 1988, from an estimated 350,000 cases in 125 countries to 74 reported cases in only two countries in 2015. One of the biggest efforts to combat polio in recent years will be launched in 2016.
The Global Polio Eradication Initiative (GPEI) from April 17 through May 1 conducted the “largest and fastest globally coordinated rollout of a vaccine into routine immunization programs in history,” according to a press release. The goal of the rollout, known as the global polio vaccine “switch,” was to provide better protection for children against polio, particularly those most vulnerable to infection.
The switch was made from the trivalent oral polio vaccine (tOPV), which protects against all three strains of the poliovirus, to the bivalent OPV (bOPV), which prevents types one and three. The third strain is no longer necessary as Type 2 polio has been eradicated. Oral polio vaccines contain a live but weakened from of poliovirus that can mutate and cause a vaccine-derived mutant form of the virus. Switching to bOPV would help protect at risk children from the return of the type two strain, which was eradicated in 1999.
Global synchronization of the switch is extremely important. If countries were to continue to use tOPVs while other used bOPV, there would be an increased risk of a return Type 2 poliovirus from mutations. However, if an outbreak of type two were to occur, a stockpile of monovalent oral poliovirus vaccine (mOPV) made to protect for Type 2 is at the ready.
Stephen Cochi, senior adviser to the Director of the Centers for Disease Control and Prevention’s Global Immunization Division, says that the stockpile is an “insurance policy in case there is an outbreak.”
The switch “is only possible due to the tremendous collaboration of country governments, GPEI partners, and the independent monitors,” says Jay Wenger, Director of the Polio Program at the Bill & Melinda Gates Foundation. “It is another example of the program moving in the right direction toward global eradication.”
The WHO is hopeful that programs such as these will lead to global eradication by the end of this year. Michael Zaffran, the WHO’s director of polio eradication, told The Guardian, “We think we could reach the point where we have truly interrupted the transmission at the end of the year.” So far this year, 13 global cases have been recorded, three of which are vaccine-derived.
Due to the risk of vaccine-derived polio, researchers are searching for less dangerous and risky forms of inactivated polio vaccines (IPV). New research published by Dutch scientist in PLOS Pathogens may have engineered a new type of polio vaccine that could eradicate polio for good.
Developing a polio vaccine derived from so-called “cold-adaptive strains,” a noninfectious version of the virus, researchers have discovered that the virus can only multiply in temperatures lower than the human body.
Voice of America reports, “The cold viral strains contained in the vaccine were genetically engineered so they are able to grow well at 30 degrees Celsius but not at all at 37 degrees, the normal human temperature. That means if there were an accidental release and a human were to come into contact with the poliovirus, it couldn’t grow and multiply inside the person.”
Jerome Custers, senior vaccine scientist at Jannsen Infectious Disease and Vaccines in the Netherlands describes the importance of such types of polio vaccines to the VOA: “You really need viruses that are safer to work with, so less virulent, not disease-causing.”
The newly developed vaccine is still in its early stages but if it could be mass-produced and synchronized globally like the most recent rollout, it could put an end to the virus entirely.
– Michael A. Clark