**1. Introduction**

Despite significant effect of current ten points mastitis control measures when fully adopted, especially on contagious mastitis pathogens, these measures are not equally adopted by all farmers, and mastitis continues to be the most common and costly disease of dairy cattle throughout the world.

Despite decades of research to develop effective vaccines against major bacterial mastitis pathogens such as *Staphylococcus aureus*, *Streptococcus uberis*, and *E. coli*, in dairy cows, effective intramammary immune mechanism is still poorly understood, perpetuating reliance on antibiotic therapies to control mastitis in dairy cows. Dependence on antibiotics is not sustainable because of its limited efficacy and increased risk of emergence of antimicrobial-resistant bacteria that pose serious public health threats. Most vaccination strategies for prevention of mastitis have focused on the enhancement of humoral immunity. Development of vaccines that induce a protective cellular immune response in the mammary gland has not been well investigated. The ability to induce cellular immunity, especially neutrophil activation and recruitment into the mammary gland, is one of the key strategies in the control of mastitis, but the magnitude and duration of increased cellular recruitment into the mammary gland will lead to a high number of somatic cells and poor milk quality. So the sustainable control measure is to develop effective vaccines that can induce potent and effective balanced (cellular and humoral) immunity, which prevents production loses and reduces clinical severity of mastitis without stimulating a marked inflammatory response of long duration.
