Abstract
BackgroundThe reported cases with varicella have not decreased and outbreaks of varicella among vaccinated children continue to be reported 9 years after the public vaccination program in Taipei. We investigated an outbreak to determine varicella vaccine coverage and effectiveness.MethodsAn outbreak occurred in an elementary school which located in southern Taipei from April 2007 through May 2007. A retrospect cohort study was performed by using a self-administered questionnaire for parents.ResultsTen out of sixteen varicella cases were vaccinated. Overall vaccine coverage was 71.2%. The common reasons for not receiving varicella vaccine were that varicella vaccine was unavailable because the student didn't live in Taipei (29.4%) or the children could not be vaccinated due to certain illnesses (23.5%). The sensitivity and specificity of self-reported vaccination status was 0.900 (95% CI: 0.864, 0.935) and 0.611 (95% CI: 0.514, 0.701).The vaccine effectiveness was 69.3%-100.0% against any disease severity of varicella. Overall vaccine effectiveness against moderate or severe varicella was 85.5%. Attending cram school was associated with the risk of developing the varicella illness (RR: 13.39; 95% CI: 5.38, 33.31). Unvaccinated students tended to show moderate to severe (>50 lesions) afflictions of the disease (RR: 4.17; 95% CI: 1.15, 15.14).ConclusionsBecause of the low vaccination coverage, varicella outbreaks continue to be reported in Taipei. Increasing vaccine coverage and second dose vaccination for increasing vaccine effectiveness may be considered.
Highlights
The reported cases with varicella have not decreased and outbreaks of varicella among vaccinated children continue to be reported 9 years after the public vaccination program in Taipei
A routine varicella vaccination for all children born after 2003 and aged 12 months or older was implemented in Taiwan since 2004
We investigated a varicella outbreak of 16 cases which, occurred on April 4, 2007, in an elementary school to determine vaccine coverage and effectiveness, and to compare disease severity among vaccinated and unvaccinated students
Summary
The reported cases with varicella have not decreased and outbreaks of varicella among vaccinated children continue to be reported 9 years after the public vaccination program in Taipei. A live attenuated varicella vaccine was made commercially available in Taiwan in September 1997. It has been included in public vaccination programs in Taipei city and Taichung city/county since 1998 and 1999 respectively [1]. It could be provided by self-paid option in other areas of Taiwan. Some studies show complications and significantly declined hospitalization rates after vaccine introduction in Taiwan [3,4], the reported cases with varicella has not decreased and outbreaks of
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