Investigation on serum pertussis toxin antibody levels in children aged 0-14 in Hangzhou

Jie CHEN; Jiying XIAO; Li ZHANG; Jun ZHOU; Suling WU

ABSTRACT

Objective:

To investigate the serum antibody level in children with pertussis in Hangzhou city, and to evaluate the incidence of pertussis in children and the immunization effect of vaccine.

Methods:

A retrospective study was conducted.The pertussis toxin IgG antibody levels in 1 486 children aged 0-14 who received physical exa-mination in Hangzhou Children′s Hospital from January to December 2018 of were collected and analyzed.Serum antibody level ≥30 IU/mL was considered seropositive.The children enrolled were divided into the 0-3-year-old, 4-6-year-old, 7-9-year-old and 10-14-year-old groups; then the children under 3 years old were subdivided into groups of 0-<3 months, 3-<6 months, 6-<9 months, 9-<12 months, 12-<18 months, and 18-≤ 36 months; finally, the children were grouped according to their vaccination times, the pertussis toxin IgG antibody level and the infection rate of pertussis were compared among different groups by Mann- Whitney U, Kruskal- Wallis and χ2 tests.

Results:

The overall positive rate of the pertussis toxin IgG antibody was 23.62% (351/1 486), and the median antibody concentration was 6.60 IU/mL.Among children aged 0-14, the 0-3-year-old children had the highest positive rate of the pertussis toxin IgG antibody and the highest median antibody concentration, which were 24.58% (29/118) and 6.95 IU/mL, respectively.There was no significant difference in the antibody positive rate and the median antibody concentration among different age groups (all P>0.05). Among different subgroups of children aged 0-3, the pertussis toxin IgG antibody positive rate and the median antibody concentration were statistically significant (all P<0.05). It was predicted that the pertussis infection rate in children over 3 years old in Hangzhou was about 45.99%.The patients receiving more than 3 doses of vaccination accounted for 87.48% (1 300/1 486), and their antibody positive rate was 25.46% (331/1 300). After excluding unvaccinated children, the comparison results suggested that there was statistical significance in the antibody positive rate and median antibody concentration among different vaccination groups ( χ2=24.467, 67.438, all P<0.001).

Conclusions:

The serum pertussis toxin IgG antibody positive rate in children aged 0-14 in Hangzhou is low, but their predicted pertussis infection rate is higher.Children aged 0-14 are easy to become a main source of infection.Therefore, it is necessary to pay attention to and strengthen the vaccination plan and research, enhance the monitoring of the infection source, and prevent the " recurrence of pertussis" .