# Investigation and analysis of pertussis antibody levels among healthy people in Hangzhou, Zhejiang Province from 2021 to 2024

## TL;DR

This study measured pertussis antibody levels in healthy people in Hangzhou from 2021 to 2024 to assess population immunity and identify groups at higher risk of transmission.

## Contribution

The study provides new insights into pertussis immunity trends across age groups and vaccination intervals in a specific geographic region.

## Key findings

- The overall antibody positive rate was 37.50% with a geometric mean concentration of 51.54 U/mL.
- Higher antibody levels were observed in 1- and 2-year-olds compared to younger and older age groups.
- Suboptimal antibody levels in adolescents and adults suggest a need for booster vaccinations to reduce transmission risks.

## Abstract

This study aims to investigate the levels of pertussis antibodies among the healthy population in Hangzhou, Zhejiang Province from 2021 to 2024. The goal is to understand the immune status of the population regarding pertussis, providing a basis for assessing the epidemiological risk of pertussis.

A multi-stage stratified sampling method was employed, categorizing the population into 11 age groups. From 2021 to 2024, one district/county was selected each year to collect blood samples from healthy individuals. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum pertussis Immunoglobulin G (IgG) antibodies.

A total of 1,352 participants were included in the study. A definite history of vaccination was documented in 65.09% of the study subjects. The overall positive rate of antibodies in the healthy population was 37.50%, with a geometric mean concentration (GMC) of 51.54 U/mL (95% CI: 47.82–55.34). Statistically significant differences were observed in the positive rates and GMC values of pertussis IgG across different years, age groups, vaccination histories, and intervals between primary and last doses. Notably, the positive rate and GMC value in 2023 and when the interval between the first and last doses was less than 1 year were the highest within the corresponding subgroups (p < 0.05); The GMC values for the 1-year and 2-year age groups were 87.60 IU/mL and 99.01 IU/mL, respectively, which were significantly higher than those in individuals under 1 year and over 10 years of age. No statistically significant differences were found in the positive rates and GMC values of pertussis IgG between different genders and regions (p > 0.05).

Suboptimal pertussis antibody levels in specific age groups, particularly among adolescents and adults, may contribute to an increased risk of transmission. Therefore, it may be worthwhile to consider booster vaccinations for these at-risk populations including the introduction of the vaccine for adolescents and adults, such as Tdap vaccine. In parallel, establishing a standardized testing and surveillance system would be essential for evaluating population immunity and mitigating future outbreak risks.