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Vitamin B12 is a water-soluble vitamin and an important micronutrient with critical role in DNA, protein, and lipid synthesis. It is responsible for one-carbon metabolism and cell division of nervous and hematopoietic cells. Among its various functions, the role as immunomodulator in cellular immunity, especially in elevating the number of CD8+ cells and NK cells, atracts scientiic interest. Many alternative anticancer and anti-inlammatory treatments involve the use of B12 together with other vitamins and nutrients, but still the scientiic information is too obscure and insuicient. Controversial data link tumorigenesis with either increased or decreased B12 blood levels in diferent types of cancer. Dietary intake and additional supplement with the vitamin do not protect against cancer risk, but the dominant opinion is to integrate B12 as part of rational and healthy nutrition to ensure proper function of the immune system. This chapter will review in brief the most important facts for vitamin B12 functions and properties. We will try also to present in concise way the human immune system and the exact role of B12 in immune activity with emphasis on the questionable participation of vitamin B12 in the process of carcinogenesis and its signiicance as anticancer immunotherapy.Keywords: vitamin B12, immunonutrition, immunomodulation, immunotherapy, tumorigenesis, cancer, inlammation IntroductionCancer is the inal outcome of uncontrolled overgrowth of normal cells. Cancer cells remain insensitive to antiproliferative signals and apoptosis. As a result, they replicate, proliferate, and invade ininitely and aggressively. Although the genetic events are thought to be the most important in the process of carcinogenesis, other factors can facilitate abnormal cell development. For many years, inlammation and anti-inlammatory response were widely associated with malignancy [1, 2] and recognized as major elements that trigger carcinogenesis.© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Extended inlammation, especially in chronic infections, predisposes to cancer, but still the mechanism(s) involved is (are) not deinitely known. Usually all inlammatory processes are followed rapidly by anti-inlammatory defense response-excessive production of proinlammatory signals (mediators) and reactive oxygen and nitrogen species. The pro-inlammatory mediators (cytokines, chemokines, and eicosanoids) may stimulate proliferation of both untransformed and tumor cells [2]. The reactive oxygen and nitrogen species lead to oxidative stress and damage of macromolecules, especially DNA to increase the risk of genetic mutations and tumorigenesis [3].A continuously increasing number of microelements, vitamins, and mineral salts are reported to modulate the immune response and counter the inlamm...

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Background: Seasonal influenza vaccination is recommended for certain at-risk groups in Bulgaria, but vaccine coverage and the population’s perception of vaccination are currently unknown. The objective of this study was to assess the level of seasonal influenza vaccination in Varna Region, Bulgaria. It also aimed to investigate the status of knowledge and the attitude towards the reliability, safety, and other aspects associated with the use of influenza vaccines. Methods: A cross-sectional survey was conducted among 120 responders in Varna Region, Bulgaria. They completed a questionnaire assessing the practice, knowledge, and attitude towards seasonal influenza vaccination. Results: Nearly 70% of all responders have never been vaccinated against seasonal influenza in their lives. The main reason indicated was a lack of confidence in the vaccine in general (53.7% of nonvaccinated responders). Individuals with insufficient knowledge, or with a negative perception, were more likely to not be vaccinated: being poorly informed and having a negative attitude towards influenza vaccination also decreased the chance of being vaccinated by 29% and 36%, respectively. Conclusions: This study indicates that efforts should be made towards achieving better understanding and knowledge of the vaccine’s mechanism of prevention and effectiveness among the Bulgarian population.

Background: Hepatitis A virus (HAV) infection is an acute, self-limited liver disease transmitted usually through the faecal-oral route via person-to-person contact. Bulgaria has intermediate HAV endemicity with higher susceptibility among adults and recurrent outbreaks. Aim: As HAV infection is strongly related to human movements and represents a significant risk to travelers and migrants, as well as to local population receiving these groups, we set out to analyze the epidemiological data on hepatitis A in five of the largest tourist border regions of Bulgaria located in its eastern part: Varna, Shumen, Dobrich, Burgas and Yambol. Materials and methods: We reviewed retrospectively all reported cases of acute hepatitis A in the eastern regions of Bulgaria over a 7-year period between 2008 and 2014. Results: A total of 2879 newly infected patients were registered during the study period, the number varying widely: from 190 cases in 2014 to 923 in 2012. The average incidence of HAV was higher in the south-eastern regions than in the northeastern regions (55.30%000 vs 15.04%000 respectively, p < 0.0001). The most affected age group in all regions was the 5-9-year olds (p < 0.0001) and males were significantly more susceptible to HAV (p = 0.02). Conclusion: Hepatitis A is still a major public health problem in Bulgaria; there is a significant difference in the incidence of the disease between the regions in the south-east and those in the north-east and between the different age groups and sexes.