Pediatr Infect Dis J. 2018 Apr;37(4):324-328. doi: 10.1097/INF.0000000000001761.
California experienced pertussis epidemics in 2010 and 2014, with more than 9000 and 11,000 reported cases, respectively. Using an ecologic study design, we compared age-specific pertussis incidence for persons ≤20 years of age in California in 2010 and 2014 to describe any changes in disease burden that may be attributable to changes in pertussis vaccination policy that occurred during interepidemic years.
We evaluated California pertussis surveillance data for reported pertussis cases 20 years of age and younger with disease onset from January 1, 2010 to December 31, 2010 or from January 1, 2014 to December 31, 2014. Age-specific pertussis rates were calculated for each of the epidemic years. Characteristics of each age group were compared across epidemic years and age-specific rate ratios (RRs) and associated 95% confidence intervals (CIs) were calculated.
In both years, the highest disease rate was reported in infants <6 months of age; however, the incidence of pertussis declined significantly among infants <6 months of age in 2014 compared with 2010 (RR 0.58, 95% CI: 0.53-0.63). Incidence remained stable among infants ≥6 months of age, children and adolescents <12 years of age (RR 1.1, 95% CI: 0.5-1.3). Adolescents 12-18 years of age had significantly higher rates of pertussis in 2014 compared with 2010, with the highest rates observed among 14- to 16-year-olds (RR 6.5, 95% CI: 5.4-7.8).
A 42% reduction (53%-63%) in pertussis incidence among infants <6 months of age in 2014 after the routine prenatal Tdap vaccination recommendation suggested that an increase in prenatal Tdap coverage has been having some impact on infant pertussis. The excess number of cases observed in 2014 compared with 2010 occurred almost exclusively among the 12- to 17-year-old age group. Among older children, the peak age of pertussis is shifting, consistent with aging of the acellular pertussis vaccine cohort.
2010 年和 2014 年，加利福尼亚州经历了百日咳疫情，分别报告了超过 9000 例和 11000 例。本研究采用生态研究设计，比较了 2010 年和 2014 年加利福尼亚州≤20 岁人群的百日咳发病率，以描述在流行间期可能由于百日咳疫苗接种政策变化而导致的疾病负担变化。
我们评估了 2010 年 1 月 1 日至 2010 年 12 月 31 日或 2014 年 1 月 1 日至 2014 年 12 月 31 日期间发病的≤20 岁报告百日咳病例的加利福尼亚州百日咳监测数据。计算了每个流行年份的年龄特异性百日咳发病率。比较了每个流行年份和年龄特异性率比（RR）的年龄组特征和相关 95%置信区间（CI）。
在这两年中，发病率最高的是<6 个月的婴儿；然而，与 2010 年相比，2014 年<6 个月的婴儿百日咳发病率显著下降（RR0.58，95%CI：0.53-0.63）。≥6 个月婴儿、儿童和青少年<12 岁的百日咳发病率保持稳定（RR1.1，95%CI：0.5-1.3）。12-18 岁青少年 2014 年百日咳发病率明显高于 2010 年，14-16 岁青少年发病率最高（RR6.5，95%CI：5.4-7.8）。
2014 年常规产前 Tdap 疫苗推荐后，<6 个月婴儿百日咳发病率下降 42%（53%-63%），表明产前 Tdap 覆盖率的增加对婴儿百日咳产生了一定影响。与 2010 年相比，2014 年观察到的病例数过多，几乎完全发生在 12-17 岁年龄组。在较大的儿童中，百日咳的发病高峰年龄正在转移，与无细胞百日咳疫苗接种人群的老龄化一致。
