The Effectiveness of Coxiella burnetii Vaccines in Occupationally Exposed Populations: A Systematic Review and Meta‐Analysis

Abstract

To estimate the effect of vaccination in preventing acute Q fever in individuals occupationally exposed to Coxiella burnetii, a systematic review and meta-analysis were undertaken in controlled trials and observational studies. Publications were obtained through a scoping study of English and non-English articles, and those reporting a commercially licensed or licensable vaccine compared with an unvaccinated or placebo control group were included in the review. Two authors performed independent assessment of risk of systematic error and data extraction. One controlled trial and five cohort publications met the inclusion criteria. All trials used a Henzerling phase I vaccine. A random-effects meta-analysis estimated significant protection in abattoir workers (RR = 0.07; 95% confidence interval [CI] 0.02-0.22) compared with the control individuals. In individuals with rare or sporadic contact with the abattoir, a significant benefit of vaccination was also found (RR = 0.06; 95% CI 0-0.93). Overall, the vaccine effectively prevented acute Q fever in individuals responsible for handling animals or their products and those working in the abattoir but not directly exposed to animals (RR = 0.06; 95% CI 0.02-0.18). Caution must be taken when interpreting the effect of C. burnetii vaccination as significant heterogeneity amongst publications was observed. A meta-regression found no significant univariate associations. This may reflect the uncertainty provided by reported data in the cohort publications. Potential systematic biases were present in the publications, and evidence included may not be sufficiently robust to extrapolate the effect of vaccination on occupationally exposed groups beyond the population of abattoir employees in Australia where all included studies occurred.

A systematic review and meta-analysis of factors associated with anthelmintic resistance in sheep

“…There was variable risk of systematic bias in many studies, which is similar to findings reported by other recent SRs and MAs in the veterinary field (Mederos et al, 2012;Belo et al, 2013;Downes et al, 2013;O'Neill et al, 2013). Most of the observational studies included in this review had a high or unclear risk of selection bias, either because insufficient information on selection of the sample population was provided, or because a purposively selected sample was used.…”

The epidemiology of Q fever in Queensland, Australia and effectiveness of vaccination for prevention

“…The observation that there is more than 93% probability of staying free of Q fever infection for more than 20 years following vaccination is evidence of the high efficacy of Q-VAX ® and confirms the results of previous studies that did not have access to data from the Q fever Vaccination registry ). In addition, the hazard of Q fever infection in vaccinated individuals was 0.10 (95% CI: 0.05, 0.16) compared to unvaccinated individuals (i.e., vaccinated individuals were 90% less likely to be infected with Q fever) is consistent with study by O'Neill, et al (2014) which showed Q-VAX ® to be highly efficacious providing 93% protection (O'Neill, Sargeant & Poljak 2014). These efficacy estimates are also in keeping with a systematic review that determine that vaccine efficacy ranged between 83-100% (Chiu & Durrheim 2007).…”

“…Additional evidence has been provided in several previous studies on the effectiveness of the Q fever vaccine. For instance, up to 93.0% protective efficacy among abattoir workers was evidenced from a met-analysis (RR = 0.07; 95% CI: 0.02 -0.22) (O'Neill, Sargeant & Poljak 2014). Moreover, in the early study of the vaccine by Marmion et al (1984), around 2.5% (34 cases in 1349) incident cases of Q fever were reported in unvaccinated workers (Marmion, BP et al 1984).…”

“…Prevention of Q fever in Australia is through targeted immunization especially in those working in, or associated with the meat industry using the locally produced Q-VAX ® vaccine (Seqirus, Australia), which has high efficacy in adults (Marmion, BP et al 1984;Marmion, BP et al 1990). Q-VAX ® is reported to provide up to 93% immune protection (O'Neill, Sargeant & Poljak 2014) with long-lived immune responses to infection with C. burnetii . However, the incidence of Q fever in people working in the red meat industry remains relatively high.…”

An outbreak of Q fever associated with parturient cat exposure at an animal refuge and veterinary clinic in southeast Queensland

“…Individuals who reported receiving Q fever vaccine more than six weeks prior to the onset of the first case were deemed to be at low risk of infection 21 and were excluded from analysis. Risk ratios were calculated, comparing cases and non‐cases, for visiting the livestock area, cat impound and dog impound, and for specific workplace activities within these areas.…”