A record high pertussis epidemic occurred in Denmark from August 2023 to February 2024, with the highest incidence among adolescents. The peak incidence in infants was lower than in previous epidemics (2019 and 2016), though the proportion of infants under 2 months hospitalized was higher. One infant died, highlighting the severity of the disease in the youngest age group. Pertussis vaccination in pregnant women was introduced in January 2024 as part of the national vaccination programme. Improved surveillance of vaccinations in pregnant women is being implemented. Pertussis is a highly contagious respiratory infection caused by *Bordetella pertussis*, affecting all ages, but infants are at highest risk of severe disease and death. In Denmark, pertussis infections are laboratory notifiable, and data are collected through the Danish Microbiology Database (MiBa). The incidence increased significantly in 2023, reaching five times the interepidemic level, peaking in November at 337 cases per 100,000 population. The incidence declined in January and February 2024. Among children under 2 years with pertussis in 2023, 37.9% were unvaccinated, 48.1% had received one or two vaccinations, and 14.1% had received all vaccines before 2 years of age. Approximately 85% of pregnant women in Denmark were vaccinated with DTaP during 2023, which may have contributed to the lower hospitalization rates among infants. The vaccination of pregnant women has been endorsed as a permanent part of the national vaccination programme. The high case load may reflect a population with many susceptible individuals, possibly due to 'immunity debt' after the COVID-19 pandemic. Public health initiatives in Denmark aim to ensure timely childhood vaccinations through electronic reminders and health visitors acting as 'vaccination ambassadors'. Despite increased vaccination coverage, pertussis remains a public health concern, with regular epidemics occurring even in highly immunized populations. The epidemic highlights the need for continued surveillance and targeted vaccination strategies to protect infants.A record high pertussis epidemic occurred in Denmark from August 2023 to February 2024, with the highest incidence among adolescents. The peak incidence in infants was lower than in previous epidemics (2019 and 2016), though the proportion of infants under 2 months hospitalized was higher. One infant died, highlighting the severity of the disease in the youngest age group. Pertussis vaccination in pregnant women was introduced in January 2024 as part of the national vaccination programme. Improved surveillance of vaccinations in pregnant women is being implemented. Pertussis is a highly contagious respiratory infection caused by *Bordetella pertussis*, affecting all ages, but infants are at highest risk of severe disease and death. In Denmark, pertussis infections are laboratory notifiable, and data are collected through the Danish Microbiology Database (MiBa). The incidence increased significantly in 2023, reaching five times the interepidemic level, peaking in November at 337 cases per 100,000 population. The incidence declined in January and February 2024. Among children under 2 years with pertussis in 2023, 37.9% were unvaccinated, 48.1% had received one or two vaccinations, and 14.1% had received all vaccines before 2 years of age. Approximately 85% of pregnant women in Denmark were vaccinated with DTaP during 2023, which may have contributed to the lower hospitalization rates among infants. The vaccination of pregnant women has been endorsed as a permanent part of the national vaccination programme. The high case load may reflect a population with many susceptible individuals, possibly due to 'immunity debt' after the COVID-19 pandemic. Public health initiatives in Denmark aim to ensure timely childhood vaccinations through electronic reminders and health visitors acting as 'vaccination ambassadors'. Despite increased vaccination coverage, pertussis remains a public health concern, with regular epidemics occurring even in highly immunized populations. The epidemic highlights the need for continued surveillance and targeted vaccination strategies to protect infants.