A Guide to Childhood Immunizations

MMR, DPT, HiB and OPV — sounds like gibberish. In fact, immunization against infectious diseases is one of the most important things you can do to protect your child's health. Together with sanitation, these practices have accounted for the great success the developed world has had in reducing childhood mortality. Widespread use of vaccines has resulted in the global eradication of small pox and dramatic reductions in the incidence of other diseases. Polio has been eradicated from the Americas, and the incidence of diphtheria, measles and rubella have all decreased by more than 99% since these immunizations were introduced.

Modern vaccines are very effective and very safe. Each vaccine, however, is associated with some adverse affects, which may range from very mild to life threatening, and each vaccine falls short of 100% effectiveness. The incidence of side effects is exceedingly small, but fear of adverse reactions, together with the fact that many parents of vaccine-age children have never seen the devastation of a polio or measles outbreak, have led to a decrease in the number of children who are protected from "childhood diseases."

The practice of immunization began in 1796 with Edward Jenner's demonstration that milkmaids who had contracted cowpox were immune to smallpox. He inoculated the fluid from cowpox blisters into the skin of susceptible individuals and induced protection against smallpox. Immunization is the practice of artificially inducing immunity or providing protection from disease. The preparations may be oral or injected. They may be killed or attenuated (weakened) live microorganisms or fractions thereof, or they may be toxoids (modified bacterial toxins that have been rendered nontoxic but that are still able to stimulate formation of antitoxin), or they may be ready-made antibody.

Measles is caused by the rubeola virus; it is highly contagious, cough, and cold symptoms, followed by a characteristic rash. Most children recover without complications, but 1 in 1000 to 1 in 2000 patients with measles develops encephalitis. This is seen as a headache, seizures, and a change in state of consciousness. Many of those who recover from encephalitis have permanent neurologic impairment. Involvement of the respiratory tract is also part of the usual course of measles, and may lead to bacterial pneumonia. Pneumonia accounts for about 60% of deaths in infants dying from measles; death due to complications of encephalitis is more often seen in children aged 10 to 14 years.

The measles vaccine was developed in the early 1960s. Early vaccines made from killed rubeola, and were withdrawn in 1968 after the recognition of atypical measles in recipients of this vaccine. The currently available vaccine is a live, weakened virus. Two doses are recommended for most children. As with other live vaccines, it should not be given to pregnant women or to patients whose immune systems are compromised except under special circumstances. Fever occurs in 5-15% and transient rashes in about 5% of vaccinees. Encephalitis occurs in less than 1 in 1 million vaccinees. The vaccine is greater than 95% effective.

Mumps is a virus in the Paramyxovirus family. The patient experiences inflammation of the parotid salivary glands, resulting in fever, pain, and swelling on one or both sides of the face. Encephalitis, meningitis, or orchitis (inflammation of the testicles) may also occur. Less common complications include arthritis, pancreatitis, oophoritis (inflammation of the ovaries) and EKG changes. Mumps vaccine is live, weakened virus, and it provides at least 90% immunity. Adverse effects, including parotitis and orchitis, are very rare. Rubella virus causes German measles and the congenital rubella syndrome. Rubella in children is a mild illness, with swollen lymph nodes in the neck and a rash that starts on the face and moves down the body. Adults are usually more ill, with fever, loss of appetite, and often arthritis or painful joints. In approximately 1 in 3000 cases of rubella, the number of platelets drops and external or internal bleeding may occur. One in 5000 cases will develop encephalitis; adults are more frequently affected than children. When a pregnant woman acquires rubella, the consequences may be fetal death, premature delivery, and a number of birth defects, including deafness, blindness, heart defects, mental retardation and others. During the first two months of gestation the fetus has a 40-60% chance of being affected, with an outcome of either multiple congenital birth defects and/or spontaneous abortion. Chances of birth defects decrease as the maternal infection occurs later in pregnancy. Rubella vaccine (live, weakened virus) may cause fever, lymph node swelling and joint pain. Complications are more common in adults than in children, and are more common in women over 25 years of age. The incidence of joint complications, even in adults, is less after vaccination than after natural rubella. Immunity is greater than 95% after immunization.

Diphtheria is caused by the bacteria Corynebacterioum diphtheriae. The name diphtheria comes from the Greek root for leather, which describes the tough membrane that forms across the back of the throat. The bacteria infect the throat and cause fever, sore throat, and development of a membrane that spreads and may block the airway. Additional complications from diphtheria are: 10-25% develop heart problems such as arrhythmia and heart failure, nerves may also be affected, resulting in weakness or paralysis. The illness can be treated with an antitoxin (made in horses), but it is effective only if given very early in the illness. Antibiotics are also important to stop toxin production, although it can not neutralize the toxin which has already been released. The immunization against diphtheria is greater than 95% effective at preventing illness and infection. After the initial series of immunizations is complete, boosters should be given every 10 years. A less potent preparation is given to persons older than 7 years, because local reactions are more severe in adult and older children. Local tenderness is frequent, but fever or other side effects are rare.

Pertussis/whooping cough is caused by the bacteria Bordetella pertussis. In China the illness is known as "the cough of 100 days." This describes the later stages of the illness. Early on, symptoms are similar to a common cold. Many children "whoop" as they gasp during coughing spells. Coughing is often severe enough to cause cyanosis (turning blue due to a lack of oxygen), and coughing fits generally end with vomiting. Patients, especially infants, may need hospitalization because of pneumonia or the need for supplemental oxygen. Prolonged coughing spells may cause nosebleeds, bleeding into the brain, collapsed lung, hernias, and rectal prolapse. Two forms of vaccine are available: Whole cell vaccine is associated with a high rate of adverse side effects. More than 50% of recipients have local reactions or fever. Prolonged crying occurs in approximately 3%, and a high-pitched, unusual cry is seen in 1 of every 1000 doses given. Convulsions occur in 1 of 1750 vaccinations. Pertussis vaccine has also been associated with acute encephalopathy with permanent brain damage. Serious neurologic illness associated with whole cell pertussis vaccine is estimated at 1 in 140,000. Because of these reactions, an acellular pertussis vaccine has been developed, and its use has almost completely replaced the older preparation. This vaccine has a much lower rate of side effects, although immunity decreases over time.

Tetanus/lockjaw is caused by Clostridium tetani. Uncontrolled muscle spasms occur as a result of the toxin it produces. This illness is frequently fatal. The bacteria, found in soil, and its spores can survive in a dry environment for years. When these spores enter the skin through a wound, the toxin enters nerve cells and travels toward the spinal cord where it causes strong muscles spasms. The incubation period is usually about 2 weeks, but may be as long as several months. Tetanus can be prevented by immunization, boosters are recommended every 10 years. In the U.S., most cases of Tetanus occur in individuals over 50 who have not kept their boosters current. Local soreness and fever are frequent, but serious adverse reactions are rare.

Polio (Poliomyelitis, infantile paralysis) is caused by the poliovirus. It is transmitted person to person, usually by the feces/oral route. More than 90% of people who are infected with polio do not develop any symptoms. Approximately 4% to 8% develop "abortive polio" with nonspecific symptoms such as fever, headache, and sore throat. Meningitis can occur. Paralytic polio occurs in .1% to 1% of infected individuals. It begins with a mild illness that rapidly progresses to include muscular pain and an asymmetric paralysis. If nerves that supply the muscles of breathing are involved, respiratory failure may occur. There is no specific treatment for polio. At least partial function usually returns to affected muscles, but a recurrence or progression of weakness may occur several decades after the original illness. Two vaccines are available to prevent polio. Live, attenuated oral poliovirus vaccine (OPV) is more than 95% effective, but it has potential to cause disease in the recipient. The overall risk of vaccine associated paralytic polio (VAPP), including both recipients and contacts (since it is excreted in the feces) is about 1 case in 2.4 million doses of OPV. The risk is highest after the first OPV dose. About 8 to 10 cases of VAPP have occurred in the U.S. each year since the introduction of OPV in 1961. An enhanced formulation of the inactivated polio vaccine (eIPV) was licensed in 1987. It is well tolerated and no serious adverse reactions have been associated with its use. It provides immunity almost equal to OPV, and because it is a killed vaccine, recipients pose no risk to household members who are not properly immunized. Many pediatricians are now recommending that the first 2 doses of polio vaccine be eIPV, but there is some controversy because of public health implications. Check with your child's pediatrician for recommendations.

Hemophilus influenza type B was the most common cause of bacterial meningitis in young children before an immunization was developed. It can also cause serious skin and soft tissue infections, epiglottitis, sinus and ear infections, and pneumonia. The vaccines licensed in 1985 and 1987 have changed this. Local reactions at the injection site occur in about 19% and fever in less than 1% of vaccinees.

Chicken Pox (Varicella) is extremely contagious, but usually not dangerous. It occurs seasonally and in epidemics, and causes a rash with low-grade fever. The rash has a characteristic appearance "dew drop on a rose petal", and begins on the trunk and face before spreading peripherally. New crops of lesions continue to appear over 2-4 days, so lesions in all stages are found in the first half of the illness. There are approximately 100 deaths per year in the U.S. from this infection. For the normal child, mortality is less than 2 per 100,000 cases. This risk increases over 15-fold for adults. Children who are not immunized are also at greater risk for serious complications. These complications include secondary bacterial infection of the skin lesions, encephalitis, and pneumonia. Varicella in newborns has a high death rate when maternal disease develops within 5 days before or 2 days after birth.

Varicella has also been associated with Reye Syndrome, a seriousness illness that can cause liver failure and brain swelling. Aspirin seems to make this syndrome more likely, so aspirin is not recommended in varicella infection. Herpes zoster or shingles, may occur decades after chicken pox infection - skin in a band on one side of the body or face develops a rash similar to the chicken pox rash, and the patient is often left with lingering pain in that area. Chicken Pox may be prevented by the use of live, attenuated varicella vaccine. This vaccine produces immunity in greater than 95%. Side effects include a varicella-like rash near the injection site (usually just a few lesions) and occasionally a fever. The need for a booster is not yet known, but will probably be recommended. The use of this vaccine has been somewhat controversial, primarily because of concerns about development of chicken pox as an adult, after immunity from the vaccine has waned. Opinion now is that the vaccine should be given to most, if not all, children who have not already had chicken pox. Ask your child's physician if it is appropriate for your child.

Hepatitis B (serum hepatitis) is caused by a virus that is transmitted by blood or sexual contact or from mother to child in the womb or by breast feeding. Hepatitis is characterized by jaundice (yellowing of the skin and eyes), nausea, vomiting, and abdominal pain. In 10-20% of patients a serum sickness-like syndrome, with fever, rash, hives, and joint pain during the incubation period of acute hepatitis. Most hepatitis B infections are self-limited, but a few patients may develop chronic hepatitis, with later development of cirrhosis or liver cancer. Worldwide, hepatitis B is the most common cause of liver cancer. Chronic hepatitis B infection is also associated with polyarteritis nodosa, a seriousvasculitis, and kidney disease. The hepatitis B immunization now available is a synthetic protein that mimics the surface antigen of the natural virus. Three doses are required to assure immunity; younger persons tend to have better antibody responses that older ones. Adverse effects of the immunization occur rarely-they consist of local reactions or low-grade fever.

The immunization of children against childhood diseases is one of the greatest success stories in medicine. Though not perfect, immunizations have saved or enhanced the quality of many lives. Research is ongoing in the search for safer, more convenient immunizations.

Dr. E. Patricia Gill is board certified in internal medicine. She joined Longmont Clinic in April 1995.