Background: This multicenter study was undertaken to investigate the serologic evidence of antibodies to Bordetella pertussis toxin (IgG-PT) in children and adolescents.
Methods: IgG-PT value in a single serum collected from 1616 children and adolescents was measured by enzyme-linked immunosorbent assay in the Food and Drug Administration (FDA)-units per milliliter from November 2008 to October 2009. The relationship between time since infection and IgG anti-PT levels were analyzed and the estimated age-specific incidences of infection were calculated.
Results: The sera IgG-PT geometric mean concentrations of the samples were 1.7 FDA-U/mL. The sera protective rates of all the subjects were 6.6% (95% confidential interval [CI]: 5.4%, 7.8%). The rates in the group aged 2 years was 9.2% (95% CI: 3.5%, 14.9%), which was significantly higher than in those aged ≥3 years (χ2 = 1615, P = 0.000). In the group aged ≥3 years, 4.0% (95% CI: 3.0%, 5.0%) of the individuals tested showed an IgG-PT level ≥40 FDA-U/mL, which was equivalent to an estimated incidence of B. pertussis infection of 7000 (95% CI: 5300, 8800) per 100,000 population per year in the year before serum sampling. There were 2 peaks of estimated incidence. One peak incidence of 9100 (95% CI: 4300, 14000) per 100,000 population per year was found in the population aged >6 to 8 years. Another peak was in the population of 12- to 20-year olds with the estimated incidence of 14,600 (95% CI: 9100, 20100) per 100,000 per year.
Conclusions: The levels of protective antibodies against pertussis were very low in the immunized children aged 2 to 20 years. A booster dose of immunization for older children or adolescents should be an urgent priority. Moreover, using enzyme-linked immunosorbent assay to determine the efficiency of vaccines and even to obtain the serodiagnosis would be beneficial in controlling pertussis.
From the *The Clinical Microbiology Lab, Department of Nosocomial Infection Control, The Children's Hospital of Fudan University, Shanghai, China; and †Department of Infectious Disease, The Children's Hospital of Fudan University, Shanghai, China.
Accepted for publication January 5, 2011.
Supported by Project of public health and clinical surveillance of vaccine controlling diseases of China Preventive Medicine Association (CPMA) [CPMA issue (2008), No.202], and Project of the key disciplines construction of public health of Shanghai (08GWZX0102).
Cooperation Units: The Children's Hospital of Fudan University; Paediatrics of Xinhua Hospital of Jiaotong University; The Children's Hospital of Chongqing Medical University; The Children's Hospital of Kunming; Pediatric department of the Second Hospital of Yinchuan.
Address for correspondence: Qi-rong Zhu, MD, Department of Infectious Disease, The Children's Hospital of Fudan University, Shanghai 201102, China. E-mail: firstname.lastname@example.org.
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