贵州省儿童百日咳疫苗全程免疫1年后百日咳丝状血凝素IgG抗体水平的时间变化特征

Levels of IgG antibody against pertussis filamentous hemagglutinin over time among children of Guizhou province from one year after completing full-series pertussis vaccination

目的 探讨儿童百日咳疫苗全程免疫1年后百日咳丝状血凝素IgG(FHA-IgG)抗体水平随时间的变化。方法 于2019-2020年在贵州省27个监测县区选取全程接种4剂次百日咳疫苗1年后的≤7岁儿童,采集血清标本,采用酶联免疫吸附试验测定FHA-IgG抗体,分析抗体浓度≥20IU/mL和≥80IU/mL的率。应用限制性立方样条(RCS)拟合二元Logistic回归模型,分析FHA-IgG抗体水平的比值比(OR)随免疫后时间变化。结果 在11 270名儿童中,百日咳FHA-IgG抗体浓度≥20IU/mL和≥80IU/mL的率分别为18.31%(2 064名)和2.61%(294名)。RCS拟合模型显示,儿童百日咳疫苗4剂次免疫1年后FHA-IgG抗体浓度≥20IU/mL的OR呈逐渐上升线性趋势(总体Wald χ^(2)=98.76,P<0.001;非线性Wald χ^(2)=8.02,P=0.091),抗体浓度≥80IU/mL的OR呈波动性上升线性趋势(总体Wald χ^(2)=69.24,P<0.001;非线性Wald χ^(2)=5.14,P=0.399)。结论 儿童百日咳疫苗全程免疫1年后百日咳FHA-IgG抗体水平随时间推移呈上升趋势,提示儿童百日咳感染风险逐渐上升,部分儿童可能存在急性或近期感染。

Objective To describe levels of IgG antibody against pertussis filamentous hemagglutinin(HFA-IgG) over time among children of Guizhou province starting one year after completion of full-series pertussis vaccination.Methods We recruited children ≤7 years of age who had completed their 4-dose series of pertussis vaccine at least one year earlier in any of 27 surveillance counties/districts of Guizhou province during 2019-2020. We collected serum samples and tested them for FHA-IgG antibodies using an enzyme-linked immunosorbent assay to determine whether the children had FHA-IgG concentrations ≥20 IU/mL and ≥80 IU/mL. We used a restricted cubic spline(RCS) method to fit a binary logistic regression model of the time-dependent odds ratios(ORs) of FHA-IgG antibody levels being above the two threshold values.Results Among the 11 270 children studied, the overall rates at which FHA-IgG antibody concentrations were ≥20 IU/mL and ≥80 IU/mL were 18.31%(2 064 children) and 2.61%(294 children), respectively. The RCS model showed that the ORs for FHA-IgG antibody being ≥20 IU/mL more than one year after completing their 4-dose series of pertussis vaccine showed a gradually increasing linear trend(total Wald χ^(2)=98.76, P<0.001;nonlinear Wald χ^(2)=8.02, P=0.063). The ORs of FHA-IgG antibody being ≥80 IU/mL showed a fluctuating, increasing linear trend(total Wald χ^(2)=69.24, P<0.001;nonlinear Wald χ^(2)=5.14, P=0.399).Conclusions Levels of IgG antibody against pertussis FHA gradually increased over time in Guizhou children after one year following completion of full-series pertussis vaccination. This gradual increase in FHA-IgG suggests a continuing risk of pertussis infection, as some children may have been infected after vaccination.