Why do we have the biggest pertussis outbreak in the last sixty-five years in Primorje-Gorski Kotar County?
Autori:
Morana Tomljenović
Sažetak
Summary
The Republic of Croatia recorded the largest pertussis outbreak in the past sixty-five years in 2023/2024 with 6564 cases (rate 169.5/100,000). During the outbreak, Primorje-Gorski Kotar County reported 395 pertussis cases (rate 148.8/100,000). Aim: To describe probable causes of the outbreak, the features of the pertussis outbreak in Primorje-Gorski Kotar County in 2023/2024 and preventive measures against pertussis that preceded the epidemic. Participants and methods: Data from reports of infectious diseases of the Department for Epidemiology of Communicable and Chronic Non-Communicable Diseases of the Teaching Institute for Public Health (TIPH) of the Primorje-Gorski Kotar County from 2023 to mid-2024 were used. We classified cases of pertussis as confirmed, probable, or possible using the national case definition. The Health and Statistical Yearbook of the TIPH provided data on vaccination coverage against pertussis for primary, first, and second booster from 2011 to 2023. Also, the indication for vaccination during the outbreak and the number of persons vaccinated at the Department for Epidemiology of Communicable and Chronic Non-Communicable Diseases of the TIPH were collected. Results: There were 187 (47.3%) male and 208 female (52.7%) cases of pertussis. The median age was 13 years (Q1–Q3; 11–17). The highest incidence was recorded among cases aged 10 to 14 (rate 1457.1/100,000). No deaths were recorded. In total, 46.6% (184/395) of the cases were fully vaccinated. Between 2011 and 2023, the coverage for the second vaccine booster dose experienced the most significant decrease (y= -1.5731x + 94.517, p<0.05). During the epidemic, 188 pregnant women, 26 health workers, and 100 contacts of newborns were vaccinated. Conclusion: Smaller outbreaks of pertussis occur every few years. This large epidemic was probably caused by the decline of vaccination against pertussis, and additionally by loss of immunity after vaccination over time. The implementation of epidemic measures during the COVID-19 pandemic prevented natural immunization
through exposure to pertussis. The 2023/2024 pertussis outbreak indicated the need for an additional booster dose against pertussis at school age.