South Carolina health officials reported at least 124 new measles cases since last Friday, bringing the state’s outbreak total to 434. More than 400 people are currently in quarantine as authorities work to limit additional spread.
The outbreak has been unfolding since early October, with most cases concentrated in Spartanburg County along the North Carolina border.
National measles outbreaks rose sharply in 2025
Measles activity increased nationwide last year, with CDC data showing nearly 50 outbreaks in 2025—up from 16 in 2024 and four in 2023. The agency says almost 90% of cases were linked to outbreaks.
Health officials also recorded at least three U.S. measles deaths in 2025, including two unvaccinated school-aged children in Texas and one unvaccinated adult in New Mexico—the first U.S. measles deaths reported in a decade.
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Vaccination guidance and effectiveness
The CDC recommends two doses of the MMR vaccine: the first at 12 to 15 months, and the second between ages 4 and 6. The CDC says one dose is about 93% effective against measles, while two doses are about 97% effective.
CDC data from 2025 shows the vast majority of cases occurred in people who were unvaccinated or whose vaccination status was unknown, with smaller shares among those who received one dose or the recommended two doses.
Coverage continues to lag below herd immunity threshold
Vaccination rates have been slipping in recent years. CDC data shows 92.5% of U.S. kindergartners received the MMR vaccine during the 2024–2025 school year, down from 92.7% the year before and 95.2% in 2019–2020, before the COVID-19 pandemic.
Sources:
AP News / South Carolina confirms 124 new measles cases as outbreak grows
CDC / Measles Cases and Outbreaks
CDC (MMWR) / Measles Update — United States, January 1–April 17, 2025
