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  • What Is Vaccine-Derived Polio And How Can My Child Be Protected From It?

    The polio outbreak has been traced back to a weakened form of the virus used in vaccines.
    by Kitty Elicay . Published Oct 22, 2019
What Is Vaccine-Derived Polio And How Can My Child Be Protected From It?
PHOTO BY Department of Health (Philippines)/Facebook
  • Since polio re-emerged in the Philippines on September 2019, the Department of Health (DOH) has been aiming to vaccinate more than a million children below the age of 5 against the disease. Starting October 14, 2019, a mass vaccination program was launched in cities and provinces in Metro Manila and Mindanao, with DOH representatives going door-to-door to provide oral polio vaccines (OPV) to children.

    Polio, which can cause paralysis and even death in some cases, has no cure. It can only be prevented with several doses of oral and injectable vaccines. According to the World Health Organization (WHO), the risk of the disease spreading in the Philippines is high because of low immunization rates.

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    In addition, the polio outbreak has been traced back to a weakened form of the virus used in vaccines. Called vaccine-derived polio, it is excreted by people after they are vaccinated. This has made parents worried about the effectivity of vaccines in preventing this highly contagious and deadly disease.

    Heidi Larson, an anthropologist who heads the Vaccine Confidence Project at the London School of Hygiene and Tropical Medicine, and author of the upcoming book Stuck: How Vaccine Rumors Start — And Why They Don’t Go Away clarifies in an interview with PRI’s (Public Radio International) The World some details about this type of poliovirus.

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    What is vaccine-derived polio?

    The inactivated polio vaccine (IPV) contains a "killed" poliovirus while the oral polio vaccine (OPV) contains a weakened version of the virus,. “It doesn’t make you sick, but it goes right through you into the environment,” says Larson, who has been involved in the global campaign to eradicate polio. “If there’s no protection in the environment, that live virus can travel to somebody else.”


    How are people infected with vaccine-derived polio?

    For example, after a child gets vaccinated and defecates, and his bowel gets into the water, the virus will start to circulate. If a population is severely under-immunized, the excreted virus can continue to circulate for an extended period.

    “And then it mutates and it becomes infective for other people. Part of the reason it’s happening is because we’ve eliminated the wild virus from most of the world. So when it does circulate, it becomes much more potent,” shares Larson.

    Larson further explains that the cases in the Philippines are because “they didn’t have that protective cover that the vaccine allows when everybody gets it.” That’s called herd immunity, where infections and illnesses don’t spread as easily because enough people in a community are vaccinated against a certain disease.

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    Can the polio vaccine still protect my child against vaccine-derived polio?

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    Yes, and they are very effective. According to the WHO, when immunization activities are poorly conducted, a population is left susceptible to poliovirus. “The problem is not with the vaccine itself, but low vaccination coverage,” adds the WHO.

    To ensure your child is protected, follow the childhood immunization schedule provided by the DOH. Four doses of the polio vaccine, whether OPV or IPV, is needed to complete the primary series for polio vaccination.

    Thanks to the mass vaccination program in the country, Larson says people are starting to believe in vaccines again. “There’s been a big investment in trust-building and we’ve gone back and resurveyed the population. ‘What are you thinking about vaccines? Do you think they’re effective? Do you think they’re important? And actually, the confidence is starting to come back,” she says.

    “These things take time, and you need to stay very vigilant," Larson adds.


    The mass vaccination program will run until October 27, 2019 in Metro Manila. Click here for the list and schedule of hospitals that offer the vaccines for free.

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