China has adjusted immunization schedules for a vaccine that protects infants against whooping cough in response to an increase in infections in recent years, the National Administration of Disease Control and Prevention said this week.

Under China's current national immunization program, a combination vaccine that prevents diphtheria, tetanus and whooping cough will be delivered at three, four, five and 18 months of age and a booster shot that protects against diphtheria and tetanus will be delivered at 6 years old.

Starting on Jan 1, 2025, a combined dose against all three diseases will be administered at two, four, six and 18 months of age as well as 6 years old, according to a notice released by the administration and five other government departments on Thursday.

Whooping cough, also known as pertussis, is a contagious disease characterized by intensive, prolonged coughing that can stretch two to three months. The disease can infect people of all ages, but is most commonly seen in infants and young children who are at high risk of developing serious complications and even dying of infection.

In China, whooping cough is classified as a Class B infectious disease that is on par with the COVID-19 disease and HIV/AIDS. A vaccine against the disease was first included in the national immunization program in 1978 and the annual number of infections had been successfully kept under 3,000 for years.

The vaccination schedule for the combo shot is altered as whooping cough infections in China and abroad are rising, said the administration.

China reported over 334,000 whooping cough cases with 23 deaths in the first half of this year, compared with less than 6,200 cases during the same period last year.

Shen Hongbing, director of the administration, said during an academic conference in March that the incidence rate of whooping cough in China began trending upward around 2014 due to various factors, including growing public awareness, improved sensitivity of surveillance networks, as well as a drop in vaccination coverage in some regions and waning immunity induced by vaccines.

Li Xiaocui, deputy director of the administration's immunization planning department, said during a news conference on Friday that the adjustment is aimed at strengthening protection for infants and school-age children amid rising risks.

Li added that China's national immunization program now includes 14 types of vaccines that can protect against 15 contagious illnesses and the immunization rate among targeted children have maintained above 90 percent.