Cow mastitis is one of the main factors of economic damage in modern animal husbandry. It is registered to affect almost everywhere, taking into account the subclinical form from 30% to 50% of the livestock per year. Economic losses of farms from the diseases of cows with mastitis are due to a decrease in milk productivity, precocious cow disposal, a decrease in the grade and sale price of market milk, and treatment costs. This study aimed to use a safer method in the prevention and control of mastitis in cows, and vaccinations could be a solution to this problem. Vaccination promotes acquired immunity to a specific pathogen and also has few side effects. A bacteriological study of clinical and subclinical forms of mastitis was conducted to study the etiology of mastitis in cows in various farms of Kazakhstan. A total of 1,068 milk samples from 767 cows were examined. The studies were carried out according to "Guidelines for bacteriological studies of milk and udder secretions of cows". The primary selection of cultures was carried out based on growth characteristics on media and microscopy of preparations from individual colonies. Morphological, cultural, and biochemical properties of the isolated cultures were studied according to generally accepted schemes. Identification of the selected cultures was carried out using Bergey's determinant. The strain numbers of Staphylococci, Streptococci, Escherichia, Klebsiella, Diplococci, and Protea were 590 (55.2%), 240 (22.4%), 151 (14.1%), 50 (4.7%), 24 (2.3%), and 13 (1.3%), respectively. The greatest strain numbers of Staphylococci (n=351) and Streptococci (n=129) were isolated from cow's milk with subclinical mastitis. The effectiveness of the polyvalent vaccine used was determined by the manifestation of clinical and subclinical forms of mastitis. Out of 600 immunized cows, 9 (1.5%) and 13 (2.3%) animals developed subclinical and clinical mastitis, respectively. Furthermore, out of 150 cows taken into control, 12 (8%) and 10 (6.6%) animals developed subclinical and clinical mastitis, respectively. Furthermore, out of 12 cows with clinical mastitis, 5 cows previously had a subclinical form. Vaccination takes a significant place in the control of infectious diseases. The success of vaccine prevention depends on the quality of vaccines and timely vaccination coverage of threatened populations. Modern immunology and vaccine prevention have summed up the theoretical basis and outlined ways to improve vaccines in the direction of creating new harmless effective vaccines.