Recent increase in pertussis incidence in Korea: an age-period-cohort analysis

Kim, Chanhee; Yi, Seonju; Cho, Sung-il

doi:2021.43.0.e2021053

Epidemiol Health > Volume 43; 2021 > Article

Original Article

Epidemiology and Health 2021;43: e2021053-0.
DOI: https://doi.org/10.4178/epih.e2021053 Published online Aug 18, 2021.

Recent increase in pertussis incidence in Korea: an age-period-cohort analysis

Chanhee Kim¹

, Seonju Yi²

, Sung-il Cho³

¹Department of Disease Control Policy, Gyeonggi Provincial Government, Suwon, Korea
²Central Disease Control Headquarters, Korea Disease Control and Prevention Agency, Cheongu, Korea
³Graduate School of Public Health, Seoul National University, Seoul, Korea

Correspondence Sung-il Cho ,Email: scho@snu.ac.kr

Received: Apr 11, 2021 Accepted after revision: Aug 18, 2021

Abstract

OBJECTIVES:
Pertussis or whooping cough—one of the most contagious diseases—is caused by the Gram-negative bacterium Bordetella pertussis. Despite a high vaccination rate, Korea recently experienced a resurgence of pertussis. This study explores patterns and possible explanations for this resurgence through an age-period-cohort analysis.
METHODS:
Using secondary data from the infectious disease portal of the Korea Disease Control and Prevention Agency and the Korea Statistical Information Service of Statistics Korea, this study analyzed the incidence of pertussis in Korea to determine which factors contributed to the recent increase using an age-period-cohort model.
RESULTS:
Analysis of the age effect indicated that the age group most vulnerable to pertussis was 0-year to 2-year-olds. Analysis of the period effect showed a sharp increase in the incidence rate after 2016. Analysis of the cohort effect showed a significant decrease in incidence beginning with the 1955 birth cohort, with the risk increasing again with the 2000s birth cohort.
CONCLUSIONS:
Previous studies have suggested 3 main possible explanations for our results. First, the increased incidence rate can be attributed to contact rates. Second, the rate of immunity through natural exposure has decreased due to the low number of circulating pathogens, in turn affecting the trend of infection. Lastly, variations in pathogens may have also contributed to the increase in incidence. Given that the most significant increase in incidence was observed among infants younger than 1 year old, sufficient maternal immunity must be prioritized to provide passive immunity to newborns via the placenta.

Keywords: Vaccines, Immunization, Whooping cough, Pertussis, Age-period-cohort analysis