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Two types of vaccines
In order to understand the effects and side effects of vaccines, we need to understand that there are two main types of vaccines, namely live “attenuated” vaccines and killed vaccines.
Live "attenuated" vaccines (such as vaccines against measles, mumps, rubella, and the oral vaccine against poliomyelitis), are solutions of the micro-organisms which have been altered in such a way as to render them incapable of producing the original disease, but capable of stimulating an immune response. These are the most successful types of vaccines, generally providing life-long protection.
Killed vaccines (such as vaccines against Hepatitis B, diphtheria, tetanus, whooping cough and influenza) are solutions of dead micro-organisms which can still produce an immune response. They include inactivated bacterial toxoids (e.g. tetanus), whole or partial virus preparations (e.g. flu) and proteins made by recombinant DNA technology (e.g. Hepatitis B). They require a primary course of immunisation, usually two to three injections spaced at intervals. Often booster immunisation is needed approximately every five to ten years if immunity is to be maintained.
Generally speaking live vaccines should not be given to individuals who are pregnant, those with severe immune deficiency diseases, or people who are immune suppressed due to illness or therapy. However, measles, oral poliomyelitis or tuberculosis vaccines should be given to HIV infected persons who are not severely ill.
Mild side effects of vaccinations
Local reaction (pain, swelling and redness at the site of the injection), fever and systemic symptoms (irritability, grumpiness, malaise and non-specific symptoms) can result as part of the normal immune response. Pain, swelling and redness can be expected in about 10 percent of vaccine recipients and fever in about 10 percent or less. This can be treated in the same way as any fever and pain, with paracetamol syrup and TLC.
In addition, some of the vaccine’s components (such as albumin adjuvant, mercury, formaldehyde, gelatin, yeast, antibiotics or preservatives) can lead to reactions. Many parents were concerned about the safety of thimerosal, a mercury-containing preservative.
Aluminium salts, which are used in vaccines to enhance the immune response, are also safe, as are levels of antibiotics and various other substances used in vaccines. Possible rare problems may come from gelatin and egg proteins also found in vaccines. Children allergic to either gelatin or eggs may have severe reactions, which is why doctors need to pay particular attention to this issue. Otherwise, the amounts of various metals and other compounds in vaccines are just too small to cause any concern, according to the study.
Persons with a history of egg or albumin allergy should not receive the yellow fever vaccine or the influenza vaccine. Vaccine viruses propagated in chicken fibroblast cells (such as the measles and MMR vaccines) can usually be given to such individuals without problems.
Generally, doctors advise that children who have more than a mild viral illness when it is time to vaccinate, should rather be vaccinated as soon as they are better.
Serious side effects
Life threatening side effects may occur, but are extremely rare. Let’s have a look at the efficacy and safety of a series of vaccines.
Polio vaccine. There are two types of polio vaccine namely the inactivated polio virus (IPV), also known as the Salk vaccine, which is given by injection and the oral polio vaccine (OPV). Polio is a potentially devastating disease and may result in paralysis.
Concerns: Recent reports of outbreaks of polio associated with the live polio vaccine, have been found to be exaggerated. Paralysis as a complication of the polio vaccine is extremely rare and occurs in two per million people who receive the vaccine, with a higher risk in adults than in children. Bear in mind that the incidence of paralysis in naturally contracted polio is considered to be “high”. In addition, between two and five percent of children and 15 to 30 percent of adults with paralysing polio, die.
Hepatitis B vaccine. Hepatitis B is endemic in Africa, which is why routine immunisation of children has been introduced fairly recently. It is a serious disease of the liver, for which there is no cure, and may lead to death or chronic liver problems, which may persist into adult life.
Concerns: There are four controversial adverse events associated with Hepatitis B vaccines: multiple sclerosis (MS), chronic fatigue syndrome (Yuppie flu), diabetes and Guillain Barré syndrome. Careful scrutiny of the use of 12 million doses of vaccine between 1991 and 1994 showed lack of evidence to link the vaccine with MS. The link with Yuppie flu seems to be merely a rumour. There is no indication at all that Hepatitis B vaccine causes type 1 diabetes. Current data also indicate no link between the vaccine and Guillain Barré syndrome.
BCG vaccine against tuberculosis is required in some countries. Globally, TB causes over three million deaths annually. The efficacy of BCG vaccines varies throughout the world from 0 to 80 percent.
Concerns: Extremely rare complications include bone infection occurring in 100 to 1000 per million doses, and TB meningitis in two per million doses. The risk to develop TB meningitis as a complication of TB illness is much higher than to develop it after a BCG shot.
DPT and DT vaccine. These are inactivated toxoids (toxins), producing immunity against diphtheria, tetanus and pertussis (whooping cough), or just diphtheria and tetanus.
Diphtheria is a severe infection of the throat in which a membrane forms which can block the airway and cause the child to smother and die. It used to occur in epidemics. Even with treatment, between five and 10 percent of diphtheria patients die. The death rate for untreated cases is 40 – 50 percent. The effect of vaccination against diphtheria lasts for about ten years.
Tetanus, also known as lockjaw, is a serious illness caused by the bacterium Clostridium tetani. It is present worldwide and can affect any age. The death rate is high in children and the elderly. Some people may survive with irreversible brain damage. The effect of vaccination lasts for about ten years.
Pertussis, although a mild illness in older children, is associated with complications in children under one year and is particularly dangerous to those under one month. Since the 1980s, it appears to be making a comeback, not only in young children, but also in older children and adults. Researchers ascribe this re-emergence to the fact that parents choose not to vaccinate their children. Worldwide, pertussis causes 300 000 deaths per year. If not immunised, you will have a 90 percent chance of contracting the disease if you come in contact with an infected person. The effect of the vaccine lasts for about 12 years.
Concerns: Pertussis vaccine has received sufficient bad press to result in lack of vaccination in some countries, leading to outbreaks of the disease. There is an extremely small, less than one in a million, chance of serious neurological complications from this vaccine, a 570 per million chance of seizures, and a 30 000 per million chance of inconsolable screaming for longer than three hours from pain. As a result of the neurological complications, it is never given to children who have a history of convulsions (except febrile convulsions), or to any child with an established disorder of the central nervous system, such as epilepsy, a history of collapse or shock, persistent screaming, fever over 40.5 degrees centigrade or a previous neurological reaction to the vaccine.
MMR vaccine. A triple vaccine against measles, mumps and German measles (rubella), it is often used in the private sector. Only the measles vaccine is mandatory for all patients.
Measles: Over a period of four decades, vaccination had eliminated most measles deaths. However, an estimated 745 000 children die every year (about 2000 every day) of the disease which is preventable by a safe, effective and relatively cheap vaccine. Over half of these deaths are in Africa. One in 1000 children with measles will develop encephalitis. Ten percent of children with measles encephalitis will die. Hundred percent of children who develop subacute sclerosing pan encephalitis (SSPE) will die. Risk of death from measles is five to 15 percent in developing countries, and 0 percent after vaccination.
Concerns: Shock reactions are extremely rare, usually due to a reaction to gelatin. The risk to develop post infectious encephalomyelitis was less than one per million doses. This is about 1000 times less than the risk to develop this complication from measles itself. Febrile seizures are extremely rare and may occur in 333 per million people. Transient and benign decrease in platelets occurs in one in 35 000, but will pass without consequences. It was the speculation by one research group that the measles vaccine can be related to autism, that led to major panic among parents. The alleged associations between measles and autism and Crohn’s disease are based upon weak scientific methods and have been refuted by a large volume of scientifically sound work. The ultimate green light came when 10 of the 12 authors offered a retraction of their controversial 1998 study that claimed a link between the MMR vaccine and autism. The retraction was published in January 2004 in the British medical journal The Lancet, which published the original study. Measles vaccination is recommended for children with HIV (although not for those severely ill from Aids) because they are at risk for severe measles and they tolerate the vaccine well.
Mumps: Death from the complication encephalitis is extremely rare. A well known complication is inflammation of the testes, which affect one in four children who get mumps past puberty. This may lead to sterility. About four in 100 people may develop inflammation of the pancreas, which may result in diabetes. Mumps in the first trimester of pregnancy results in miscarriage in a quarter of cases.
Concerns: One in 100 000 children will develop meningitis after vaccination, but it is mild and without long-term consequences. One in ten children with mumps will develop meningitis.
German measles (rubella): During the first 18 weeks of pregnancy, when the heart, brain, liver, eyes and other organs are developing, German measles poses a serious risk to the foetus. It can lead to deafness, mental retardation, blindness and other eye defects, and heart defects. There is an 80 percent risk that one or more of these features will occur if the mother contracts the infection in the first trimester of pregnancy. One in 1500 people with German measles has a bleeding complication due to a drop in blood platelets, and one in 6000 develop encephalitis.
Concerns: Transiental joint symptoms develop in up to 25 percent of post pubertal females due to rubella vaccines. All women of childbearing age should be vaccinated against German measles. Although vaccination during pregnancy is not advocated, rubella vaccine is of no consequence to the foetus during pregnancy, according to WHO experts.
The Hib vaccine. This vaccine protects against serious meningitis caused by a bacterium called Haemophilus influenzae type B. The vaccine contains only the coat proteins of the bacterium, and is safe and effective.
Concerns: Serious adverse events are uncommon, making it one of the safest vaccines currently available. People with HIV tolerate Hib vaccination well.
For more information on care and support of tuberculosis visit South African National TB Association (SANTA) or phone them on 011 454 0260.
February 2007
