CONTEXT: Limited data are available on the contagiousness of vaccinated varicella cases. OBJECTIVES: To describe secondary attack rates within households according to disease history and vaccination status of the primary case and household contacts and to estimate varicella vaccine effectiveness. DESIGN, SETTING, AND PATIENTS: Population-based, active varicella surveillance project in a community of approximately 320,000 in Los Angeles County, California, during 1997 and 2001. Varicella cases were reported by child care centers, private and public schools, and health care clinicians and were investigated to collect demographic, clinical, medical, and vaccination data. Information on household contacts' age, varicella history, and vaccination status was collected. MAIN OUTCOME MEASURES: Varicella secondary attack rate among household contacts; vaccine effectiveness using secondary attack rates in unvaccinated and vaccinated children and adolescents. RESULTS: A total of 6316 varicella cases were reported. Among children and adolescents aged 1 to 14 years, secondary attack rates varied according to age and by disease and vaccination status of the primary case and exposed household contacts. Among contacts aged 1 to 14 years exposed to unvaccinated cases, the secondary attack rate was 71.5% if they were unvaccinated and 15.1% if they were vaccinated (risk ratio [RR], 0.21; 95% confidence interval [CI], 0.15-0.30). Overall, vaccinated cases were half as contagious as unvaccinated cases. However, vaccinated cases with 50 lesions or more were similarly contagious as unvaccinated cases whereas those with fewer than 50 lesions were only one third as contagious (secondary attack rate, 23.4%; RR, 0.32 [95% CI, 0.19-0.53]). Vaccine effectiveness for prevention of all disease was 78.9% (95% CI, 69.7%-85.3%); moderate disease, 92% (50-500 lesions) and 100% (clinician visit); and severe disease, 100%. CONCLUSIONS: Under conditions of intense exposure, varicella vaccine was highly effective in preventing moderate and severe disease and about 80% effective in preventing all disease. Breakthrough varicella cases in household settings were half as contagious as unvaccinated persons with varicella, although contagiousness varied with numbers of lesions.
CONTEXT: Limited data are available on the contagiousness of vaccinated varicella cases. OBJECTIVES: To describe secondary attack rates within households according to disease history and vaccination status of the primary case and household contacts and to estimate varicella vaccine effectiveness. DESIGN, SETTING, AND PATIENTS: Population-based, active varicella surveillance project in a community of approximately 320,000 in Los Angeles County, California, during 1997 and 2001. Varicella cases were reported by child care centers, private and public schools, and health care clinicians and were investigated to collect demographic, clinical, medical, and vaccination data. Information on household contacts' age, varicella history, and vaccination status was collected. MAIN OUTCOME MEASURES: Varicella secondary attack rate among household contacts; vaccine effectiveness using secondary attack rates in unvaccinated and vaccinated children and adolescents. RESULTS: A total of 6316 varicella cases were reported. Among children and adolescents aged 1 to 14 years, secondary attack rates varied according to age and by disease and vaccination status of the primary case and exposed household contacts. Among contacts aged 1 to 14 years exposed to unvaccinated cases, the secondary attack rate was 71.5% if they were unvaccinated and 15.1% if they were vaccinated (risk ratio [RR], 0.21; 95% confidence interval [CI], 0.15-0.30). Overall, vaccinated cases were half as contagious as unvaccinated cases. However, vaccinated cases with 50 lesions or more were similarly contagious as unvaccinated cases whereas those with fewer than 50 lesions were only one third as contagious (secondary attack rate, 23.4%; RR, 0.32 [95% CI, 0.19-0.53]). Vaccine effectiveness for prevention of all disease was 78.9% (95% CI, 69.7%-85.3%); moderate disease, 92% (50-500 lesions) and 100% (clinician visit); and severe disease, 100%. CONCLUSIONS: Under conditions of intense exposure, varicella vaccine was highly effective in preventing moderate and severe disease and about 80% effective in preventing all disease. Breakthrough varicella cases in household settings were half as contagious as unvaccinated persons with varicella, although contagiousness varied with numbers of lesions.
Authors: Kendra Viner; Dana Perella; Adriana Lopez; Stephanie Bialek; Michael Nguyen; Niya Spells; Barbara Watson Journal: Public Health Rep Date: 2014 Jan-Feb Impact factor: 2.792
Authors: Margaret K Doll; Jennifer B Rosen; Stephanie R Bialek; Hiram Szeto; Christopher M Zimmerman Journal: Am J Public Health Date: 2014-12-18 Impact factor: 9.308
Authors: Reena H Doshi; Vivian H Alfonso; Patrick Mukadi; Nicole A Hoff; Sue Gerber; Ado Bwaka; Stephen G Higgins; Cyrus Sinai; Brian Cowell; Guillaume Ngoie Mwamba; Emile Okitolonda; Jean-Jacques Muyembe-Tamfum; Anne W Rimoin Journal: Pediatr Infect Dis J Date: 2018-02 Impact factor: 2.129
Authors: Anne A Gershon; Judith Breuer; Jeffrey I Cohen; Randall J Cohrs; Michael D Gershon; Don Gilden; Charles Grose; Sophie Hambleton; Peter G E Kennedy; Michael N Oxman; Jane F Seward; Koichi Yamanishi Journal: Nat Rev Dis Primers Date: 2015-07-02 Impact factor: 52.329