Epidemiological Characteristics of Pertussis in Hainan Province, 2023-2025.

OBJECTIVE

To analyze the epidemiological characteristics of pertussis in Hainan Province from 2023 to 2025, describe the outbreak trajectory and patterns of population susceptibility, and provide evidence for optimizing pertussis prevention and control strategies.

METHODS

Clinically diagnosed and confirmed pertussis cases reported in Hainan Province between January 1, 2023, and December 31, 2025, were retrieved from the China Information System for Disease Control and Prevention; suspected cases were excluded, yielding a total of 2,927 eligible cases.Descriptive epidemiological methods were used to analyze the temporal, geographic, and population distributions of the cases; piecewise linear regression was employed to characterize monthly trends in case counts; and multivariable logistic regression was performed to identify risk factors for hospitalization.

RESULTS

The incidence of pertussis in Hainan Province exhibited an outbreak-and-decline pattern from 2023 to 2025, increasing from 4.29 per 100,000 population in 2023 to 22.26 per 100,000 in 2024 before declining to 1.37 per 100,000 in 2025, with a statistically significant difference across the three years (χ2 = 2,888.2, P < 0.001).Piecewise linear regression showed that the monthly number of cases increased significantly during the ascending phase (β = 21.82, P < 0.001) and decreased significantly during the descending phase (β = -11.41, P < 0.001).The age distribution shifted significantly toward older children: the proportion of infants aged <1 year decreased from 43.1% to 27.3%, whereas that of individuals aged ≥1 year increased from 56.9% to 72.7%.Among cases with complete severity records after July 2024, infants aged 0-2 months had the highest risk of hospitalization and accounted for 90.0% of intensive care unit admissions.

CONCLUSION

This study shows that the 2024 pertussis outbreak in Hainan was followed by a rapid decline in 2025, with a shift toward older children and a persistently high hospitalization risk in infants aged 0-2 months. These findings support strengthening surveillance in schools and childcare institutions and evaluating the effectiveness of the 6-year DTaP booster policy, while maintaining maternal and infant protection strategies.