The decline in immunity and circulation of pertussis among Chinese population during the COVID-19 pandemic: A cross-sectional sero-epidemiological study

Abstract

BackgroundIn recent years, the resurgence of pertussis has posed a public health challenge in many countries. This study aimed to evaluate the immunity levels against pertussis among populations of different ages in China. MethodsWe conducted a cross-sectional serological survey in Zhejiang Province, China in 2020. Serum IgG antibodies against pertussis toxin (anti-PT), filamentous hemagglutinin (anti-FHA), and pertactin (anti-PRN) were quantitatively measured. The geometric mean concentration (GMC) of three antibodies was calculated. An anti-PT level < 5 IU/mL was considered undetectable, ≥20 IU/mL as seropositive and ≥80 IU/mL as an indicator of recent infection. Mathematical models were fitted for anti-PT concentrations over time in children after four doses of the pertussis vaccination. ResultsA total of 4459 participants aged 0–59 years were included in the analyses. The overall positivity rate of anti-PT was 29.80% with the highest (81.44%) rate in the 1–2 years old and the lowest (4.72%) in 10–14 years old. The GMCs of anti-PT, anti-FHA and anti-PRN for the whole participants were 9.67 (95%CI: 9.25–10.10),18.93 (18.24–19.67), and 8.99 (8.61–9.38) IU/mL, respectively. Over 50% of subjects aged ≥ 7 years had undetectable anti-PT IgG antibodies (<5IU/mL). The proportions of the populations with anti-PT IgG ≥ 80 IU/mL were approximately 0.9%, 0.3% and 1.1% among the 10–14, 15–29, and 40–59 years old groups, respectively. The power regression equation of the attenuation model after last dose of pertussis vaccine was y = 41.088x-1.238 (R2 = 0.935, p < 0.001). The fitted anti-PT concentrations was only 5.60 IU/mL at 5 years following the last vaccination dose. ConclusionThe prevalence of pertussis decreased during the study period in the COVID-19 pandemic; however, there was still a certain proportion of adolescents and adults with evidence of recent infection. The decline in antibody levels after pertussis vaccination was observed, and booster doses are in urgent need in China.