In 2016, global health officials altered the composition of the oral vaccine.
Previously, the vaccine protected against all three types of wild polio. Then they withdrew one of those types — the one that was leading to most of the vaccine-derived cases but whose wild form had
Previously, the vaccine protected against all three types of wild polio. Then they withdrew one of those types — the one that was leading to most of the vaccine-derived cases but whose wild form had
been successfully eradicated.
Vaccine-derived poliovirus of that type was still in circulation from earlier iterations of the oral vaccine — and now with the reformulated vaccine, increasing numbers of people who were no longer vaccinated against it. So there was further spread.
Vaccine-derived poliovirus of that type was still in circulation from earlier iterations of the oral vaccine — and now with the reformulated vaccine, increasing numbers of people who were no longer vaccinated against it. So there was further spread.
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