But the adrenal medulla, in contrast to the adrenal cortex, is not required for survival. In adrenalectomized patients, hemodynamic and metabolic responses to stimuli such as hypoglycemia and exercise remain normal. Exercise
One physiological stimulus to adrenaline secretion is exercise. This was first demonstrated by measuring the dilation of a (denervated) pupil of a cat on a treadmill, later confirmed using a biological assay of urine samples. Biochemical methods for measuring catecholamines in plasma were published from 1950 onwards. Although much valuable work has been published using fluorimetric assays to measure total catecholamine concentrations, the method is too non-specific and insensitive to accurately determine the very small quantities of adrenaline in plasma. The development of extraction methods and enzyme–isotope derivate radio-enzymatic assays (REA) transformed the analysis down to a sensitivity of 1 pg for adrenaline. Early REA plasma assays indicated that adrenaline and total catecholamines rise late in exercise, mostly when anaerobic metabolism commences.During exercise, the adrenaline blood concentration rises partially from the increased secretion of the adrenal medulla and partly from the decreased metabolism of adrenaline due to reduced blood flow to the liver. Infusion of adrenaline to reproduce exercise circulating concentrations of adrenaline in subjects at rest has little hemodynamic effect other than a slight β2-mediated fall in diastolic blood pressure.
Hepatitis A vaccine is a vaccine that prevents hepatitis A. It is effective in around 95% of cases and lasts for at least twenty years and possibly a persons entire life. If given, two doses are recommended beginning after the age of one. It is given by injection into a muscle. The first hepatitis A vaccine was approved in Europe in 1991, and the United States in 1995. It is on the World Health Organizations List of Essential Medicines.The World Health Organization (WHO) recommends universal vaccination in areas where the disease is moderately common. Where the disease is very common, widespread vaccination is not recommended as all people typically develop immunity through infection during childhood. The Centers for Disease Control and Prevention (CDC) recommends vaccinating:

All children aged 12–23 months
Unvaccinated children and adolescents aged 2–18 years
International travelers
Men who have sex with men
People who use injection or non-injection drugs
People who have occupational risk for infection
People who anticipate close contact with an international adoptee
People experiencing homelessness
People with HIV
People with chronic liver disease
Any person wishing to obtain immunityIn addition, a person who has not previously received hepatitis A vaccine and who has direct contact with someone with hepatitis A should get hepatitis A vaccine within two weeks after exposure.Severe side effects are very rare. Pain at the site of injection occurs in about 15% of children and half of adults. Most hepatitis A vaccines contain inactivated virus while a few contain weakened virus.