Health | Dr Shay
Vaccinating Against Hepatitis A & B Dr Shay Keating explains how vaccinations against Hepatitis A and B work Vaccination refers to the administration of antigenic or foreign material, the vaccine to stimulate an individual’s immune system to develop immunity to a pathological organism, commonly viruses. It is the most effective method of preventing infectious diseases, and widespread vaccination is largely responsible for the worldwide eradication of smallpox. Mass vaccination has also resulted in a huge reduction in the world health burden of diseases such as polio, measles and tetanus. Most vaccines are given by injection into the muscle, as they are not reliably absorbed through the intestines if swallowed. In a sexually transmitted infection context, vaccination against hepatitis is routine in high risk cohorts, such as men who have sex with men (MSM). Currently we have only a vaccine against hepatitis A and B. There is no effective vaccine generally available against hepatitis C. In hepatitis A vaccination, the vaccine is a ‘dead’ virus, a virus 50 EILE Magazine
that has been inactivated with formaldehyde. When the vaccine is given to the person, the body thinks it has been exposed to the ‘real’ virus and makes antibodies against it. When real exposure to hepatitis A occurs, the body will have the antibodies already made and infection is aborted. The vaccination schedule for hepatitis A is 2 injections six months apart. The vast majority responds to this schedule, and no blood test is required to see if the body has made enough antibodies. As well as vaccinating high risk groups against sexually acquired hepatitis A, travelers to areas in the world where hepatitis A is endemic are offered vaccination. With hepatitis B, the vaccine does not contain the virus. It contains a part of the virus, the surface antigen. When injected into the body, an antibody to the surface antigen, called the surface antibody is made. Three vaccines are administered. At the elected (start) date, one month later and at six months. Not everyone responds to this standard schedule, and we routinely check antibody levels 2 months after completion of the vaccine administration. The level of antibodies is reported by the laboratory in milli international units per millilitre of blood
(mIU/ml blood). If the level is greater than 100 mIU/ml, this is an adequate response and no further action is required. In the future, when exposure to the real hepatitis B virus occurs, the immune system with its immune memory recognises the surface antigen of the virus, and with its antibodies to this surface antigen, kills the virus. If the vaccination response is between 10mIU/ml and 100 mIU/ ml, this is a poor response, and a booster vaccine if recommended. No further action is then needed. If, however, the level is less than 10 mIU/ml the person is a non responder. Factors that might predict a non responder are age over forty, increased body mass, male sex and immunodeficiency: advanced HIV disease or long term steroid use. Body mass or fatness of the arms is important. The needle used to inject the vaccine needs to get into the muscle. If the length of the needle is 2.5 centimetres and the fat thickness is 3 centimetres, the injection is into the tissue under the skin and not the muscle. Most non responders will respond to a course of double dose vaccine, one into each arm at each occasion, usually three at monthly intervals. It is crucial that all persons who have been vaccinated have a blood test performed, to ensure
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