34 Afsharian M et al. Figure 3. Percentage of immunized people by smoking status Discussion Zinc is an essential micronutrient for human metabolism that catalyzes more than 100 enzymes, facilitates protein folding, and helps to regulate gene expression. Patients with malnutrition, alcoholism, inflammatory bowel disease, and malabsorption syndromes are at increased risk of zinc deficiency. Symptoms of zinc deficiency are nonspecific, including growth retardation, diarrhea, alopecia, glossitis, nail dystrophy, decreased immu- nity, and hypogonadism in males. In developing countries, zinc supplementation may be effective for the prevention of upper respiratory infection and diarrhea, and as an adjunct treatment for diarrhea in malnourished children. However, current data do not support the positive effect of zinc supplementation on, wound healing, or human immunodeficiency virus. Zinc is well- tolerated at recommended dosages. However, adverse effects of long-term and high-dose zinc consumption are: effect on decrease in immunity and high-density lipoprotein cholesterol levels, anemia, copper deficiency, and possible genitourinary complications (10). All kinds of immune cells show decreased function after zinc depletion. In such situation, all functions related to monocytes and T cells are impaired, in natural killer cells and neutrophils cytotoxicity activity and phagocytosis is reduced, respectively. However, auto-reactivity and all reactivity will increase (11). In fact, enhancing the immune response to the vaccination after hepatitis B among older peoples is one of the most important issues. There are large number of studies inves- tigating the different methods for increasing the immune re- sponse after vaccination such as use of different adjuvants (such as levamisole, cimetedine and zinc sulfate), different methods of vaccination (whether intradermal or intramuscular as well as rapid or conventional methods). For example, vaccination via the intradermal route (ID) is considered as a method that may be more effective than the conventional intramuscular (IM) route (12). However, such general belief is not supported by findings from all studies (13). While other factors such as smoking status, BMI, and age may have effect on Ab production after vaccination, effect of different adjuvants have been investigated in different studies. It is generally believed that addition of levamisole to hepatitis B vaccine can enhance the immunological response (12). Regarding the use of zinc, while there are some controver- sies on the effect of zinc supplementation on immune status, it has been suggested that daily use of up to 40 mg zinc has no ad- verse effects on immune status of healthy people (14). However, different studies investigating the effect of zinc on proportion Zinc sulfate and immunologic response to recombinant hepatitis B vaccine of seroconversion showed no effect (15, 16). One study about the effect of zinc sulfate on increasing antibody response in hemo- dialysis patients was done in Italy in 1990. This study showed 50% increase in antibody production in non-responders (mean antibody production was 124.6 mIU/mL) (15). Another study on the effect of zinc sulfate on increasing antibody response in he- modialysis patients was done in Holland in 1991. In that study the patients was categorized into two groups (n=7, each group). In one group, hepatitis B vaccine with zinc sulfate was given and in another group hepatitis B vaccine without zinc sulfate was administered. Results showed no difference in antibody produc- tion between the two studied groups (16). Another study on the effect of zinc sulfate on increasing antibody response in elderly people was done in Ireland in 2007. In this study, one group re- ceived zinc sulfate capsules, 15 mg daily for six months; the other group was given 40 mg zinc sulfate daily for six months. Result showed no difference in the antibody production between the two study groups (14). According to the results of some studies that discussed previously we thought that zinc might stimulate antibody response in the non-responders to hepatitis B vac- cine. One of the most important of non-responder groups are old people. This study showed no statistical difference between the two study groups in terms of gender and weight in antibody production. Random allocation of people into two groups cre- ated a similar distribution of all background and confounding variables between two studied groups. After adjustment for all other variables, there was no effect for smoking, group and sex on seroconversion. It is worth mentioning that for the purpose of this study we used accelerated method for vaccination and that may contribute to our final results regarding no effect in the seroconversion of people allocated to two groups. Acceler- ated HB vaccination can shorten duration of immunization we performed this clinical trial for showing its effectiveness (9). Future studies should aim at investigating the effect of zinc sul- fate on seroconversion after a simple method vaccination (0, 1 m, 6 m). 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The effect of age on immunologic re- sponse to recombinant hepatitis B vaccine: a meta-analysis. Clin Infect Dis. 2002;35(11):1368-75. 7. Hashemi SA, Moghadami M, Lankarani KB, Alborzi A, Mahbudi A. The Effica- cy of Hepatitis B Vaccination among School Age Children in Southern Iran. IRCMJ. 2010;12(1):45-8. 8. Ada G. Vaccines and vaccination. N Engl J Med. 2001;345(14):1042-53. 9. Vaziri S, Janbakhsh A, Sori B. Evaluation of antibody production after hepa- titis B vaccination by simple and rapid method. Kermanshah: Kermanshah University of Medical Sciences, Center IDR; 1385. 10. Saper RB, Rash R. Zinc: an essential micronutrient. Am Fam Physician. 2009;79(9):768-72. 11. Ibs KH, Rink L. Zinc-altered immune function. J Nutr. 2003;133(5 Suppl 1):1452S-6S. Hepat Mon. 2011;11(1):32-35