FILE PHOTO: A sign reading "measles testing" is seen as an outbreak in Gaines County, Texas, has raised concerns over its spread to other parts of the state, in Seminole, Texas, U.S., February 25, 2025. REUTERS/Sebastian Rocandio/File Photo

By Julie Steenhuysen

Dec 12 (Reuters) - South Carolina health officials on Friday confirmed an additional 15 new cases of measles since Tuesday, as the widening outbreak of the vaccine-preventable disease in the northwest part of the state has infected 126 people so far.

At least 303 people exposed to the highly contagious virus have been placed in quarantine and 13 infected people are in isolation to curb the spread of the disease, the state health department said.

Thirteen of the new cases were from known household exposures, one was from a neighborhood contact and the other was from an unknown source still being investigated.

Of those infected, 119 were unvaccinated, three were partially vaccinated with one of the recommended two-dose measles-mumps-rubella vaccines, one was fully vaccinated and three had unknown vaccination status.

U.S. medical groups have grown increasingly concerned about the spread of vaccine-preventable diseases under Health Secretary Robert F. Kennedy Jr., a longtime anti-vaccine activist.

The South Carolina outbreak, which state epidemiologist Linda Bell on Wednesday described as accelerating, comes as the United States teeters on the brink of losing its measles elimination status.

A spate of large outbreaks this year kicked off with one in West Texas that infected more than 700 people and spread to several other states. In response to that, Kennedy made misleading claims about nutrition, vitamin A and other questionable treatments.

He has since increasingly raised doubts about the shot's safety and efficacy, contrary to established science, and begun a review of the U.S. childhood vaccination schedule after firing and replacing a group of independent vaccine advisers and the director of the Centers for Disease Control and Prevention.

As of December 9, the CDC has reported 47 measles outbreaks and a total of 1,912 confirmed cases of the disease in the United States this year. That compared with 16 outbreaks reported in 2024. The CDC defines an outbreak as three or more related cases.

Most of the infections have occurred in unvaccinated individuals, and three people have died, including two school-age children.

Two doses of MMR vaccine are required for school entry in South Carolina, a state that has seen sharp declines in vaccination rates since the COVID-19 pandemic.

For the 2023-2024 school year, 92.1% of kindergarten students had two doses of MMR vaccine, down from 95% in 2019-2020.

ELIMINATION STATUS THREATENED

The World Health Organization is expected to make a call in January on whether the United States keeps its measles elimination status. To be considered measles-free, a country must stop the spread of the virus and be free of locally transmitted cases of the same strain for 12 months or longer, in addition to having high-quality surveillance systems.

In November, Canada lost its measles elimination status after nearly three decades due to its failure to curb a year-long outbreak.

The United States has a deadline of January 20 to prove it halted continuous transmission of the strain that started in Texas last January 20, according to Dr. Demetre Daskalakis, a former CDC official.

Measles is highly preventable when countries attain a 95% vaccination coverage rate - the level needed for a community to achieve herd immunity that protects those unable to get the vaccine. The measles vaccine is 97% effective after two doses.

Dr. Emily Landon, an infectious disease expert at the University of Chicago Medicine, said most adults in the United States are vaccinated against measles, but rising rates of vaccine skepticism has reduced protection among children in many pockets of the country.

"If your vaccine rate isn't more than 95% of small children, you're not going to be able to keep it," she said of measles elimination status.

Measles can cause symptoms such as fever, cough and a characteristic rash. It can also lead to severe complications like pneumonia, encephalitis and death.

(Reporting by Julie Steenhuysen in Chicago; Additional reporting by Siddhi Mahatole and Sriparna Roy in Bengaluru; Editing by Alan Barona and Bill Berkrot)