Immunity duration

Sex Age (years) Number Time after immunization Duration of symptoms... 

Vitamin C status is supposed to play a role in immune function and to influence the progression of some chronic degenerative diseases like atherosclerosis, cancer, cataracts, and osteoporosis. The role of vitamin C in immune function, especially during common cold and upper respiratory tract infection, is the subject of lively debate. The exact mechanisms of action have not yet been fully elucidated, but the results of several trials point to a reduced duration and intensity of infections in subjects consuming high amounts of vitamin C (200-1000 mg/d). However, the incidence of common cold was not influenced significantly (24). 

Echinacea, a frequently used herb, is taken to stimulate the immune astern function by increasing the number and activity of immune cells and to stimulate phagocytosis (ingestion and destruction of bacteria and other harmful substanceIt appears to shorten the duration of colds and influenza. 

Scitovsky AA, Cline MW, Abrams DI (1990) Effects of the use of AZT on the medical care costs of persons with AIDS in the first 12 months. J Acquit Immune Defic Syndr 3 904-912 Seage III GR, Landers S, Lamb GA et al (1990) Effects of changing patterns of care and duration of survival on the cost of treating the acquired immunodeficiency syndrome (AIDS). Am J Public Health 80 835-839... 

Male mice exposed to 7.3 mg/kg/day for 13 weeks had significantly decreased spleen weights and decreased neutrophil counts (Hoechst 1984b), indicating that immune activity in mice may also be affected. An intermediate-duration oral MRL of 0.005 mg/kg/day was derived based on the NOAEL of 0.45 mg/kg/day for immunotoxicity identified in the Banerjee and Hussain (1986) study. In support of these positive findings, Khurana et al. (1998) observed decreased macrophage functionality, in the absence of any other apparent toxicological effects, in 1-day-old broiler chicks fed 30 ppm endosulfan in the diet for 4 or 8 weeks. 

Also, chronic-duration studies have not generally shown adverse effects on organs of the immune system. Routine gross and histopathologic examination of the lymph nodes and thymus of rats, mice, and dogs exposed to endosulfan for 2 years at doses of up to 2.9 mg/kg/day (Hoechst 1989a), 2.51 mg/kg/day (Hoechst 1988b), and 1 mg/kg/day (EMC 1967), respectively, revealed no adverse effects. However, these studies did not assess immune function directly. 

The intermediate-duration oral MRL was derived based on the observation of decreases in humoral and cell-mediated immune responses in rats consuming 0.9 mg/kg/day for 22 weeks (Banerjee and Hussain 1986). Choice of this end point is supported by the observation of similar effects in rats at higher doses following ingestion for shorter periods (Banerjee and Hussain 1986, 1987) and decreased neutrophils and... 

Immunotoxicity. Limited information is available regarding the effects of endosulfan on the human immune system. However, specially designed studies using rats indicate that both humoral and cellular immune responses are depressed by ingested endosulfan at doses that do not induce any overt signs of toxicity (Banerjee and Hussain 1986,1987). In vitro studies support the possibility that endosulfan affects immune system function (Das et al. 1988). These results demonstrate that immunotoxicity may be a more sensitive end point of endosulfan-induced toxicity than other end points, and humans may be at risk for adverse immune effects following exposure to endosulfan. An intermediate-duration oral MRL was derived based on the observation of depressed immune responses (Banerjee and Hussain 1987). 

Passively acquired immunity involves no work on the part of the body s defence mechanisms, and produces immediate protection of short duration. 

Immunosera and human immunoglobulins depend for their protective effects on their content of antibodies derived, in the case of immunosera, flxm immunized animals and, in the case of immunoglobulins, flxm humans who have been immunized or who have high antibody titres consequent upon prior infection. This form of immunity, known as passive immunity, is achieved immediately but is limited in its duration to the time that protective levels of antibodies remain in the circulation see also Chapter 16. 

Microbial risks are mostly due to single exposures (except for microbial toxins) chemical risks are affected by chronic duration of exposure. Responses to infective pathogens are probably more variable as compared to chemical agents due to different subpopulations and depending on immune status. 

The dose of the IGIM determines the duration of coverage. A dose of 0.02 mL/kg confers immunity against hepatitis A for less than 3 months and doses of 0.06 mL/kg provide immunity up to 5 months. If protection against HAV is required beyond 5 months, then readministration of IGIM may be indicated.1,5... 

Children less than 12 years of age will have a 97% seroconversion rate following a single vaccination. Adolescents and adults more than 13 years old will only have 78% seroconversion after a single inoculation, but will have 99% conversion after the second vaccination administered 4 to 8 weeks after the first. Antibody titers appear to persist for at least 20 years following immunization. Despite excellent seroconversion rates, breakthrough chickenpox is reported at a rate of 1 case per 10,000 doses distributed. Most cases occurred within the first year following vaccination, and were due to wild-type varicella zoster virus. The majority of breakthrough cases were mild and of short duration.12... 

In those with a history of VZV infection, VZV disease occurs in 30% of allogeneic HCT recipients.91 The appropriate duration of VZV prophylaxis is controversial.8 Although VZV infections are reduced by prophylactic acyclovir (800 mg twice daily), administered from 1 to 2 months until 1 year after HCT, the risk of VZV persists in those on continued immune suppression.91... 

The effects of acute- and intermediate-duration inhalation lead exposure on local and systemic immune function following intratracheal, intraperitoneal, or intravenous immunization were studied in mice continuously exposed to lead nitrate for 14 or 28 days (Hillam and Ozkan 1986). Several parameters of local and systemic immune function were measured in the immunized, lead-exposed mice. Lead content... 

Other investigators have been unable to demonstrate lead-induced effects on various components of the immune system in laboratory animals. The effects of lead exposure of varying duration on natural killer cell and T-lymphocytc function were investigated in rats. Male Alderly Park rats received lead as lead acetate in the drinking water at lead concentrations equivalent to 14.3 and 143 mg lead/kg/day for... 

Andrews, S.J., Rolph, T.P. and Munn, E.A (1997) Duration of protective immunity against ovine haemonchosis following vaccination with the nematode gut membrane antigen Hll. Research in Veterinary Science 62, 223—227. 

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