The outbreak led to more than 150 children being sent into quarantine.

A measles outbreak in South Carolina has grown to 15 cases, state health officials said on Friday.

The newly identified cases were close contacts of people who were quarantining at home and were not in any school settings when contagious, according to the South Carolina Department of Public Health (SCDPH).

"Because they were quarantining before they became infectious, no additional exposures have occurred with these new cases," the department said.

The outbreak was first identified in the South Carolina upstate region in early October, according to the SCDPH. Several of the cases have been confirmed in Spartanburg County, which sits on the border with North Carolina.

Last week, at least two elementary schools in Spartanburg County sent more than 150 unvaccinated students home to quarantine for 21 days after being exposed to measles. Since then, at least five of the 150 children have contracted the disease, officials said.

In a press conference earlier this week, South Carolina health officials said more than 100 students from Global Academy of South Carolina and Fairforest Elementary are continuing to quarantine at home.

Of the more than 600 students at Global Academy, a K-5 charter school, just 17% have their required immunizations, state health department data shows.

Meanwhile, Fairforest has a vaccination rate of 85%, according to the data. A vaccination rate of 95% is typically considered to be when a location or an area has herd immunity to help prevent outbreaks in communities.

Health officials announced earlier this week that they are deploying a mobile vaccination unit in the county over the next two weeks to provide measles, mumps and rubella (MMR) shots for free.

It comes as the U.S. is seeing the highest number of measles cases in more than 30 years, according to data from the Centers for Disease Control and Prevention (CDC).

As of Wednesday, 1,596 cases have been confirmed in 41 states, with more than 90% of cases among those who are unvaccinated or whose vaccination status is unknown.

CDC data shows 44 measles outbreaks have been reported across the U.S. so far this year, compared to 16 outbreaks reported all of last year.

The CDC currently recommends that people receive two MMR vaccine doses, the first at ages 12 to 15 months and the second between 4 and 6 years old. One dose is 93% effective and two doses are 97% effective against measles, the CDC said.

Measles was declared eliminated from the U.S. in 2000 due to the highly effective vaccination program, according to the CDC. However, CDC data shows vaccination rates have been lagging in recent years.

During the 2024-2025 school year, 92.5% of kindergartners received the MMR vaccine, according to data. This is lower than the 92.7% seen the previous school year and the 95.2% seen in the 2019-2020 school year, prior to the COVID-19 pandemic.

South Carolina measles outbreak grows to 15 cases: Health officials