“A regional outbreak of an infectious disease requires emergency mass vaccinations of about 125,000 people.” What sounds like a report from the distant past or a developing country happened only this week, in New Zealand. Measles is back.

Over the past few days, the Canterbury District Health Board confirmed 27 cases of measles. Considering that measles takes about two weeks to incubate, the disease is likely to further spread. It could take several weeks until the outbreak is under control.

Health Minister David Clark did the only responsible thing. He urged Cantabrians who have no or insufficient immunisation against the disease to get vaccinated. “Vaccines work,” the Minister said. “There is no credible science that supports the claims of anti-vaccinators that I have seen.”

It is sad it has come to that. Vaccinations against measles have been available for decades, and in 2017 the World Health Organization (WHO) even congratulated New Zealand on eliminating both measles and rubella.

As we now see, the plaudits were premature.

Though nine in 10 young children in New Zealand have received the required jabs, older groups lack in vaccinations. In any case, neither young children nor young adults reach the level of 95 percent vaccinated. This percentage marks the so-called herd immunity required to prevent sustained outbreaks.

These are the effects of a years-long campaign against vaccinations. It started with claims that some vaccines were causing serious development disorders such as autism. Though such claims have long been refuted, their effect has been to spread fear among parents, leading to fewer vaccinations.

Science is clear about vaccines. In a 2008 bulletin, the WHO said, “… vaccination has greatly reduced the burden of infectious diseases. Only clean water, also considered to be a basic human right, performs better.”

Thanks to vaccines, fatal diseases like smallpox have been eradicated and millions of lives saved worldwide. It is one of the great triumphs of modern science.

And yet, even in a developed country like New Zealand, a significant number of parents are voluntarily keeping their children from vaccinations. With each rejection, parents are not only increasing the risks for their own family but also for others in the community.

This is not to argue for mandatory vaccinations. But we should worry that science still has such a hard time against popular superstitions – with deadly consequences.