Although the varicella vaccine is not included in China’s national pediatric vaccination schedules, a one-dose varicella vaccine has been recommended for vulnerable children aged 1–12 years in Jiangsu Province. Researchers involved in this study looked at a varicella epidemic in an elementary school to see what variables contributed to varicella transmission and vaccine failure. A 1:2 matched case-control study was conducted. They enrolled two controls for each case: one with high exposure in the same classroom as the patient and one with minimal exposure in a separate classroom. During the epidemic, 51 cases were recorded, with 26 cases being breakthrough varicella. The presence of siblings and a history of varicella vaccine vaccination were protective factors in avoiding varicella infection. Contact with varicella patients increases the chance of contracting chickenpox. Breakthrough varicella patients had a milder rash, less complications, fewer rash sites, and active lesions that lasted less time. In breakthrough instances, one pneumonia case and one encephalitis case were recorded. The age of 15 months at the time of immunization increased the chance of varicella relapse. The adjusted vaccination efficacy rate was 81%.

A single dose of varicella vaccination is helpful in reducing clinical symptoms. The modest coverage offered by one dosage is insufficient to prevent varicella outbreaks, therefore vaccination after 15 months of age should be included in the immunization schedule; a two-dose approach is strongly advised.

Reference: https://www.tandfonline.com/doi/full/10.1080/21645515.2019.1665959