The number of koalas has been decline throughout the South-East Queensland (SEQ) and it’s linked to several threatening process like habitat destruction, dog attacks, motor vehicle trauma and most importantly chlamydial infection. Chlamydial infection in koalas is significant and causes infertility, morbidity and mortality. Current antibiotics approach has certain limitations like low efficacy rate for chronic infection, increased persistent infection and mostly adverse effect on the gastrointestinal microflora. So, the vaccine development would be the ideal option. Recent mathematical modelling suggests that a 5 -10 years long vaccination program could be able to reverse the population declining trends. Our vaccine research group has been developed a vaccine by using recombinant major outer membrane (rMOMP) protein as antigen. Initially, we applied immune-stimulating complex as vaccine adjuvant. Recently, polyphosphazine based poly I: C and host defense peptides are successfully employed as vaccine adjuvant. These combination adjuvants have the ability to elicit long lasting cellular and humoral immunity via a single dose vaccination. The chlamydial pathogenesis and the host immune response are the key interactive features for the efficient vaccine production. T cell through the activation of interferon gamma mediated immune response proceeded to the infection procedure. Besides, antibodies has subordinate role in the infection process but it could modulate the cellular response in several animal models. In this article, we analysed the humoral immunity both in koala that has natural live infection and/ or has received vaccine and its impact on vaccine development process. We observed current infection in koalas elicit very low level of C. pecorum specific neutralizing antibodies in vitro. Subsequently, these animals were affected by chlamydial diseases or unable to clear the infective stage. Alongside, we identified the current vaccine were able to boosted the antibody response via introducing C. pecorum specific neutralizing antibodies.