Trust in vaccines – one of the world’s most effective and widely used medical products – is highest in poorer countries but weaker in wealthier ones where skepticism has allowed outbreaks of diseases such as measles to persist, a global study found.

The United States recorded 41 new measles cases last week, bringing 2019’s total number of cases to 981 in the worst outbreak of the disease since 1992, federal health officials said.

Maine became the 25th U.S. state to confirm a case of measles amid the country’s worst outbreak of the disease in a quarter century.

The most widespread U.S. measles outbreak in a quarter-century has infected 60 new patients in the last week, raising the total number of confirmed cases to 764, federal health officials said.

Maine could soon prohibit parents from citing religious or personal beliefs to avoid vaccinating their children, making the U.S. state one of a half dozen cracking down during the nations’ largest measles outbreak in 25 years.

New York City Mayor Bill de Blasio declared a public health emergency in parts of Brooklyn in response to a measles outbreak, requiring unvaccinated people living in the affected areas to get the vaccine or face fines.