Epidemiology of Breakthrough Varicella after the Implementation of a Universal Varicella Vaccination Program in...

Area of Science:

• Epidemiology
• Vaccinology
• Public Health

Background:

• Taiwan implemented a national one-dose varicella vaccination policy in 2004 for infants at 12 months of age.
• Understanding breakthrough varicella (BV) and its risk factors is crucial for assessing vaccine effectiveness in the post-vaccination era.

Purpose of the Study:

• To evaluate the incidence of breakthrough varicella (BV) and varicella-related hospitalizations in Taiwan after the introduction of a national one-dose varicella vaccination program.
• To identify risk factors associated with BV in vaccinated children.

Main Methods:

• Retrospective cohort study using national vaccination registry and National Health Insurance data (2004-2014).
• Identified children vaccinated between 12-23 months of age.
• Utilized multiple Cox regression to analyze risk factors for BV.

Main Results:

• Overall varicella incidence decreased significantly from 4.71 to 0.81 per 1000 person-years between 2004 and 2014.
• Breakthrough varicella (BV) incidence declined from 3.90 to 1.94 per 1000 person-years over the study period.
• Females and recipients of Varivax® had a lower risk of BV compared to males and Varilrix® recipients, respectively.

Conclusions:

• The national one-dose varicella vaccination program in Taiwan has been effective in reducing overall varicella incidence and hospitalizations.
• The incidence of breakthrough varicella and related hospitalizations remained low, indicating sustained vaccine effectiveness.
• Vaccine type and sex are significant factors influencing the risk of breakthrough varicella.