Vaccine Switch Marks a New (and Hopefully Last) Stage in the Battle With Polio

Over the weekend, health officials began replacing the current polio vaccination in an effort to wipe out one of three strains of the virus

Polio Vaccine
Pacific Press/Corbis

Sunday marked the beginning of a massive synchronized switch in over 150 countries to a new version of the oral polio vaccine—a complex process that will take two-weeks to pull off. If it goes well, however, the initiative marks the next—and hopefully last—step in the fight to eradicate polio.

It’s taken 30 years of intensive immunization programs, but last year the continent of Africa did not see a single case of polio, and only 74 cases were reported worldwide, all from Pakistan and Afghanistan. According to the Global Polio Eradication Initiative, that’s down from over 350,000 cases in 1988. Now, over 1 billion people per year, mostly children, receive immunizations against polio.

The current vaccine protects against three strains of polio, but one of those variations, Type 2, has not been detected in the wild since 1999. Because the current vaccine contains a live, weakened version of Type 2 polio, a very small percentage of people vaccinated against polio could develop the disease. That’s why researchers have removed the Type 2 immunization from the new polio vaccine, preventing the possibility of it infecting someone and returning to the human population.

According to Donald G. McNeil Jr. at The New York Times, the Global Polio Eradication Initiative is coordinating the global vaccine switch, the first changeover of its type ever attempted. The Initiative is directing healthcare managers around the world to destroy the old vaccines currently stored in their refrigerated warehouses and stock the new version. But it’s not as easy as it sounds. The old and new vaccines are packaged in similar boxes, and the old vaccines need to be incinerated, boiled, autoclaved, bleached, or buried in concrete.

“This is going to be hard,” Walter Orenstein, director of the vaccine center at Emory University School of Medicine tells McNeil. “For a long time, we’ve driven people to think of [the] vaccine as valuable. Now we’re asking them to destroy it.”

Kate Kelland at Reuters reports that the Initiative and drug makers hope to remove the Type 1 and Type 3 live polio from the vaccine by 2019 or 2020 before switching to an “inactivated” polio vaccine. But that’s only if things go as planned and those two strains are also eradicated in the wild. Kelland points out that the Global Polio Eradication Initiative began in 1988 with plans to get rid of the disease by 2000. While it has reduced cases by 99 percent, stamping out the last 1 percent of infections has been tricky.

In 2011, polio from Pakistan infected people in China, and in 2013 the disease briefly re-emerged in Syria during the civil war. It persists in Pakistan and Afghanistan mainly because Islamist militants have hindered immunization efforts, attacking aid workers including a suicide bombing at a polio center in Quetta in January.

But the medical community isn’t phased by the setbacks. “Taking our foot off the pedal now could mean polio will within a few years spread straight back into large parts of the world and create 100,000 or 200,000 cases,” World Health Organization’s director of polio eradication, Michel Zaffran, tells Kelland. “The job has not been done and will not be done until we have fully eradicated the virus.”

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