Objective: To describe the epidemiological and etiological characteristics of hand, foot and mouth disease (HFMD) among children aged 5 years and younger in Ningbo after the access of entero-virus-A71 vaccine (2016 to 2019).
Methods: A retrospective cohort study were performed in children aged 5 years and younger in Ningbo from 2016 to 2019. Data for incidence of HFMD was collected from the National Notifiable Disease Surveillance Reporting System and the Electronic Medical Records (EMRs) System, while the demographic information was derived from the Immunization Information System. Speci-mens were detected by real-time fluorescence quantitative PCR and the Wilson method was used to estimate the incidence rate and 95% confidence interval.
Results: From 2016 to 2019, a total of 1 044 800 residential children were observed in this population-based cohort. In the study, 102 471 cases of HFMD were diagnosed in 2 651 081 person-years, revealing an overall incidence density of 3 865.25/100 000 person-years. There was no significant decline in the number of the cases after the vaccine was available. The number of the patients of hand foot mouth disease during the four years was 93 421, of whom 84 875 (90.85%) had only one incident record, while 8 946 (9.15%) had 2 or more cases in this period; there were 69 771 (66.06%) patients who only needed to see a doctor once for each disease, 19.92% of the patients needed to be treated twice, and 14 801 (14.02%) patients needed to go to the hospital or clinic three times or more. The incidence of HFMD showed obvious seasonality and periodicity, which mainly concentrated in April to July each year, and the epidemic cycle was 2 years; most of the cases were 1 to 3-year old children, with more cases in male. The incidence density varied across the region, with the highest density observed in Ninghai (4 524.76/100 000 person-years), followed by Xiangshan (3 984.22/100 000 person-years). In 3 748 library-conformed cases, 2 834(75.61%) were detected positive, among which enterovirus-A71, Cox-A16 and other enteroviruses accounted for 9.03%, 31.55% and 59.42%, respectively. During the study period, the cumulative coverage of enterovirus-A71 vaccine increased year by year, with the proportion of enterovirus-A71 and severe cases both gradually decreasing.
Conclusion: The current status of hand, foot and mouth disease in Ningbo is still serious. Children under 3-year old (especially male children aged 1 year) were the key population for prevention and control. Vaccination might lead to changes in major pathogenic virus type, of which more attention should be paid to the potential impact on disease surveillance, prevention and control.
目的: 描述肠道病毒71型(EV-A71)疫苗可及后的2016—2019年宁波市5岁及以下儿童手足口病流行特征及病原学情况。
方法: 采用队列设计，回顾性收集2016—2019年宁波全民健康信息平台中传染病报卡和电子病历内手足口病发病资料，人口学统计信息来源于预防接种信息系统，通过实时荧光定量PCR方法进行病毒分型。采用Wilson法估算发病密度及95%置信区间。
结果: 2016—2019年，队列累计观察5岁及以下常住儿童1 044 800人，总观察人时为2 651 081人年，期间新发手足口病102 471例，年均发病密度为3 865.25/10万人年。4年间手足口病发病人数为93 421人，其中单人单次发病为84 875人(90.85%)，单人发病2次及以上为8 946人(9.15%)；单次发病只需就诊一次者为69 771人(66.06%)，有19.92%的患者需就诊2次，而有14.02%(14 801人)的患者需就诊3次及以上。发病具有明显的季节性和周期性，主要集中在每年4至7月，流行周期为2年；绝大部分病例为1~3岁儿童，男性多于女性。各地区发病密度不同，以宁海县最高(4 524.76/10万人年)，象山县次之(3 984.22/10万人年)。病毒分型3 748例, 实验室确诊2 834例，检出阳性率75.61%，其中肠道病毒71型、柯萨奇病毒A16和其他肠道病毒分别占9.03%、31.55%和59.42%。研究期间，EV-A71疫苗累计接种率逐年升高，EV-A71型病毒占比从2016年的13.34%降低至2019年的0.71%，同期重症病例占比也从1.26%降低至0.54%。
结论: 宁波市手足口病疫情依然严峻，1~3岁以下儿童(特别是1岁男性儿童)是重点防控人群，随着疫苗接种率升高，EV-A71感染比例和重症占比均逐渐降低，应及时关注手足口病流行毒株的变化对疾病监测与防控的潜在影响。
Keywords: Epidemiological characteristics; Etiology; Hand, foot and mouth disease; Vaccination.