Aug. 1 (UPI) -- Vaccination rates among U.S. kindergarten students decreased during the 2024-2025 school year, according to data released Thursday by the U.S. Centers for Disease Control and Prevention and the District of Columbia.

Rates ranged from 92.1% for diphtheria, tetanus and pertussis to 92.5% for measles, mumps and rubella. Vaccination rates for polio and varicella dropped in more than half of the states compared to a year prior, the data show.

"The number of kindergarteners attending school without documentation of completing the MMR vaccine series was about 286,000 during the 2024-2025 school year," the report said. Overall, the number of kindergartners exempt from one or more vaccines during the 2024-2025 school year reached nearly 138,000, the data showed.

The drop in vaccination rates comes amid an uptick in the number of measles cases in the United States. There have been 29 reported outbreaks in 2025, compared with 16 in 2024.

Of 1,156 cases reported so far this year, 87% of them have been confirmed, compared to 198 of 285 confirmed cases, or 69%, in 2024.