Back Story: The pandemic and rising hesitancy slowed immunizations.
A false claim in the 1990s that said the combined measles, mumps and rubella vaccine causes autism led to a drop in immunization rates. Public health campaigns later recouped much of that deficit, but the rates again fell during the Covid-19 pandemic, particularly in low-income countries.
The measles virus is particularly adept at finding pockets of vulnerability, but outbreaks of other vaccine-preventable diseases may follow, said Dr. Saad Omer, the dean of the O’Donnell School of Public Health at U.T. Southwestern in Dallas.
“Measles is usually the canary in the coal mine,” Dr. Omer said.
In the United States this year, Philadelphia has recorded nine cases of measles, Washington State confirmed three cases and was investigating three others, and several states were tracing contacts of a single case each.
As of January, 49 countries have what the W.H.O. calls “large or disruptive outbreaks,” according to Dr. Natasha Crowcroft, senior adviser on measles and rubella at the organization.
Britain confirmed 250 measles cases in 2023, most of them in children younger than 10. In Europe last year, one in five cases was an adult 20 years or older, according to the W.H.O.
Those numbers may seem modest, but they are a sign that public health officials should step up immunization campaigns, Dr. Omer said.
“If a fire is just starting, that’s the time to go all in and douse it right away, rather than wait for it to spread,” he said.
The Red Line: Vaccination rates should not fall below 95 percent.
For measles to remain under control, at least 95 percent of a population must be immunized. In Europe, the percentage of people who had received a first dose dropped from 96 percent in 2019 to 93 percent in 2022.
More than 1.8 million infants missed their measles vaccinations between 2020 and 2022.
“We actually knew this was going to happen, so it’s not news for us,” Dr. Crowcroft said of Europe’s rise in measles cases.
“There are times when there’s absolutely no pleasure in being right, and this is one of those.”
