Vaccine hesitancy
Events following reductions in vaccination

In several countries, reductions in the use of some vaccines were followed by increases in the diseases' morbidity and mortality. According to the Centers for Disease Control and Prevention, continued high levels of vaccine coverage are necessary to prevent a resurgence of diseases that have been nearly eliminated. Pertussis remains a major health problem in developing countries, where mass vaccination is not practiced; the World Health Organization estimates it caused 294,000 deaths in 2002. Vaccine hesitancy has contributed to the resurgence of preventable disease. For example, in 2019, the number of measles cases increased by thirty percent worldwide and many cases occurred in countries that had nearly eliminated measles.
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