Epidemiological characteristics of breakthrough varicella among children born during 2011-2016 in Ningbo city
Objective To analyze epidemiological characteristics of breakthrough varicella in Ningbo children.Methods We enrolled children born during 2011-2016 who had varicella breakthrough infections after receiving varicella vaccine(VarV)that occurred on or before December 31,2020.We used case records from the China Disease Control and Prevention Information System matched with vaccination records from the Ningbo Children's Vaccination Information System.We compared reporting incidences of breakthrough varicella for 1-dose and 2-dose VarV vaccination.Results The overall incidence of reported breakthrough varicella was 142.86 per 100 000 population(920 cases).Incidences per 100 000 for 1-dose and 2-dose VarV were 590.82(520 cases)and 71.94(400 cases),respectively,with average ages of onset of 3.63±2.01 and 6.30±1.60 years.Cumulative incidences per 100 000 increased rapidly from 11.53 and 4.79 at 18 months to 140.00 and 58.76 at 36 months after 1-dose and 2-dose vaccination.Conclusions The incidence of breakthrough varicella among Ningbo children increased over time after VarV vaccination;2-dose VarV vaccination significantly reduced breakthrough incidence.
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