Covid was arguably the main reason for the drop, as it caused disruptions ranging from healthcare staff shortages, to supply chain issues. But other causes contributed , including an increase in children living in conflict or in fragile situations.

Recent outbreaks of measles and polio already show the risks connected with the steep drop in immunization.

An especially dramatic drop was in a less common vaccine, the one used against HPV. Only about 15% of the eligible girls are vaccinated against the virus, and a quarter of that coverage was lost in 2021. This is a severe setback for a vaccine introduced 15 years ago which reduces the risk of cervical cancer by close to 90%.

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