Epidemiology of varicella in Fenghua district, Ningbo, 2013–2016

Objective To analyze the epidemiological characteristics of varicella in Fenghua district of Ningbo, Zhejiang province, from 2013 to 2016, and identify the factors influencing the epidemic of varicella.

Methods Descriptive epidemiological analysis was conducted in the incidence of varicella in Fenghua during 2013–2016. The incidence trend of varicella before and after 2 dose live attenuated varicella vaccine immunization program were compared.

Results A total of 1 198 varicella cases were reported with an average annual incidence of 60.17/100 000 during 2013–2016. The incidence declined from 78.98/100 000 in 2013 to 41.91/100 000 in 2016. Compared with 2013–2014, the incidences in age group 5–9 years, 1–4 years and 15–19 years declined by 67.76%, 55.76% and 35.27%, respectively, after the implementation of 2 dose immunization program during 2015–2016, but the incidences in age group ＜ 1 years, 10–14 years and ≥20 years showed no decrease. The median age of cases increased from 9 years during 2013–2014 to 12 years during 2015–2016. The incidence of varicella in urban area was 101.92/100 000, higher than that in rural area (43.78/100 000), with statistical significance (χ²＝226.557, P＝0.000).

Conclusion The incidence of varicella in Fenghua showed a downward trend, and the median age of varicella cases has become older.