A record-breaking measles outbreak in the US has ended. It may have helped drive a spike in vaccination rates - CNN

There were nearly 1,000 confirmed cases over about six months, including at least 21 hospitalizations. No new cases associated with the outbreak have been reported in more than 42 days, the state health department said, marking two incubation periods – the time it would take to get sick after being exposed to the virus – without any transmission.

The South Carolina outbreak started in October, contributing to a record-breaking year for measles cases in the US along with the large, deadly outbreak in West Texas. The nation is on track to record even more cases this year, which would again make it the worst year since measles was declared eliminated in the US in 2000 — a status that is now under threat.

Public health experts have largely attributed the rise in measles cases in the US to falling vaccination rates; more than 90% of the cases in South Carolina — and nationwide — have been among people who had not received the measles-mumps-rubella (MMR) vaccine. The vast majority are children.

But there is a very early signal that MMR vaccination rates may have ticked up among young children in the US.

Some experts say that hearing about multiple large outbreaks and record numbers of measles cases nationwide — and confronting exposures near home — could have encouraged some hesitant parents to vaccinate their kids, and there’s “cautious optimism” about a potential shift in vaccination trends.

Safe, effective vaccines

South Carolina public health leaders say that increasing vaccination coverage played a significant role in helping to get the outbreak under control.

“Vaccination – combined with other opportunities for good, solid public health work – really can be effective, even against some of the most contagious viruses,” Dr. Brannon Traxler, deputy director and chief medical officer with the South Carolina Department of ​Public Health, said at a news briefing Wednesday.

Along with vaccination, aggressive contact tracing, case investigation and quarantine protocols helped “put a fire break ring around” the outbreak as it burned through the susceptible population, Traxler said. But the response cost the state about $2 million.

The MMR vaccine is highly effective. One dose prevents disease about 93% of the time, and two doses raise that protection to 97%.

In South Carolina, tens of thousands of MMR vaccine doses were administered during the outbreak. Doses administered in Spartanburg County, the center of the outbreak, nearly doubled compared to the previous year, and there was a 31% jump statewide year-over-year. Doses administered to children under 4 had a particularly large spike.

One metric from the US Centers for Disease Control and Prevention suggests that aligns with a broader national trend.

About 97% of 3-year-olds in the US in 2025 had at least one dose of MMR vaccine, compared with 93% of 3-year-olds in 2024, according to data from the CDC’s National Immunization Surveys.

The CDC said in an email to CNN that the increase is “consistent with a return to more typical vaccination patterns” after “disruptions in routine care and increased public distrust due to vaccine mandates and lockdowns” brought coverage down during the Covid-19 pandemic. But the data shows that it’s the first time in more than a decade that MMR coverage among this age group has ticked above 95%, a key threshold needed to prevent outbreaks of the highly contagious disease.

The sample size for this data set is small — an average of about 16,000 people each year — and data for children born in 2022, who would be 3 in 2025 during the record year for measles, is still preliminary. Some experts also question the data because some other routine childhood vaccinations didn’t show the same trend.

But others think the spike in MMR coverage tracks amid the current context.

A ‘collective remembering’

“I’ve been saying for a couple years now that I think it was going to take a resurgence of vaccine-preventable diseases in our communities for people to really understand the benefits of vaccines and the protection that they offer,” said Dr. Josh Williams, a pediatrician with Denver Health whose research has focused on vaccination trends.

“So perhaps we’re seeing a little bit more of a collective remembering of the severity of these diseases and a desire from parents to make sure that their kids are protected when the diseases are circulating in the areas where they live and play,” he said.