Outbreak of occupational Brucella infection caused by live attenuated Brucella vaccine in a biological products company in Chongqing, China, 2020

Abstract

The northern areas of China are traditional endemic regions for brucellosis in both animals and humans, while occasional outbreaks of brucellosis have been observed in neglected southern provinces. On 16 December 2020, Chongqing Center for Disease Control and Prevention (CQCDC) received a report of 15 Brucella seropositive employees in a biological products company. The CQCDC and the local health administrative department launched an investigation that included identification of cases, laboratory testing of samples, and employees’ interview to identify the cause of this incident. A case-control study was implemented to compare high-risk factors between cases and serology-negative personals. Human and animal serum samples and environmental swabs were collected for testing. A total of 61 recessive infectors were found with an infection rate of 43.57% (61/140). Fisher’s exact test showed that there were significant differences in Brucella infection rates among different post classifications ( p = 0.02), working places ( p = 0.007), and buildings ( p < 0.0001). Case-control study showed that working in vaccine production workshop was independently associated with an increased risk of infection (odds ratio ( OR ): 2.60; 95% confidence interval ( CI ): 1.31–5.19). The positive detection rate was 88.06% (59/67) for production environment and 16.67% (2/12) for external environment. The investigation indicated that close contact with biological products and aerosol were the potential transmission routes of this outbreak under the condition of insufficient personal protection and disinfection. Our study provides new epidemiological evidence for a more detailed understanding of occupational infections with live attenuated Brucella vaccine.

What risk do Brucella vaccines pose to humans? A systematic review of the scientific literature on occupational exposure

“…In Chongqing, China, Zhou et al (2022) published a seroprevalence case-control study among employees of a vaccine factory engaged in the production of A19 and S2 Brucella strains with findings similar to those of the publication described above. They reported a sero-prevalence of 43.6% (61/140), although all workers were asymptomatic and no suspected or confirmed case was found [ 6 ]. The investigation pointed out that close contact with biological products and aerosols were the potential transmission routes in the context of insufficient personal protection and disinfection.…”

“…Of the 5 vaccine strains currently used (Rev.1, S19, RB51, A19 and S2), Rev.1 seems to be the most virulent [ 7 ]. Prolonged contact with the pathogen, lack of information and instructions provided to the occupational groups exposed, and low adherence to personal protective equipment (PPE) in the work environment, appeared to be the main risk factors leading to infection by these vaccine strains [ 6 , 35 – 37 ]. Vaccine factories accidents are infrequent but can cause serious outbreaks due to aerial spread.…”

“…Vaccine factories accidents are infrequent but can cause serious outbreaks due to aerial spread. On the other hand, despite strict protection measures, a percentage of vaccine manufacturing workers developed positive serology without symptomatic illness [ 6 , 23 ]. In fact, Buchanan et al had observed in slaughterhouses that workers with positive serology showed a lower risk of acquiring brucellosis [ 38 ].…”

“…abortus A19, a strain derived from S19, is used for cattle, and B . abortus S2 strain for pigs [ 6 ].…”

Practice of standardization of CLSI M45 A3 antimicrobial susceptibility testing of Infrequently Isolated or Fastidious Bacteria strains isolated from blood specimens in Guangdong Province 2017–2021

“…However, in a report of occupational exposure to air-contaminated Brucella spp. that occurred in a bio-safety level three laboratory, the infection rate was as high as 43.6% ( Koruk et al, 2012 ; Zhou et al, 2022 ). Therefore, we believe that in clinical laboratories, which are usually bio-safety level two, the isolation of highly pathogenic Infrequently Isolated or Fastidious Bacteria such as Brucella spp.…”