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Vaccines: Protecting Individuals, Communities and the WorldVaccination is one of our biggest health success stories. Vaccines are a major reason for the improvement of personal, societal, and world health. As a result of vaccination programs, smallpox was eradicated in 1977 and polio was eradicated from the Americas in 1991. There has been a significant decline in the incidence of vaccine preventable diseases such as diphtheria, tetanus, pertussis (whooping cough), and children today are protected against many illnesses that their parents experienced. Despite these impressive benefits, parents are often concerned about the discomfort to their children and the possibility of serious side effects.
How Vaccines WorkA vaccine contains a small or modified piece of the organism that causes a disease. It is similar enough to the real organism that the body's immune system reacts by producing protective antibodies against it. It is different enough from the real organism that the vaccine recipient gets only a mild reaction rather than the actual illness. In order for vaccines to work, the body's immune system must be mature enough to recognize an invader and make antibodies against it.
Since the younger the child, the sicker they become if they catch an illness, one of the challenges in immunization science has been developing vaccines which would be capable of stimulating immune responses in very young children. There are currently vaccines that prevent children under the age of 2 years from getting 14 diseases This has resulted in a very full schedule of immunizations from infancy through toddlerhood, as many vaccines require two or more doses to produce a protective level of antibodies to fight off disease. Efforts have been made to reduce the number of needle sticks by producing combination vaccines which contain serum against more than one disease without decreasing the effectiveness of the individual components or increasing the risk of side effects.
It's easy to lose sight of the need for compliance with vaccines since their success has prevented the public from personally experiencing the devastating effects of certain illnesses. But a look at pre- and post- vaccine history and a look at the illnesses current vaccines protect against provide compelling evidence for the ongoing impact of immunizations. For example, between 1958 and 1962, five years before the MMR (measles, mumps and rubella) vaccine was licensed, there were 503,282 cases of measles in the United States. In 2004, the number of cases had dropped to 258, a greater than 99% decrease.(1)
What Diseases Can Vaccines Prevent?What follows are a few examples of diseases that are currently preventable with immunizations. See Table 1 for a complete vaccination schedule.
Hepatitis B : Hepatitis B virus (HBV) is transmitted from one person to another through blood and body fluids, and primarily infects the liver. In the United States, it is most commonly spread through sexual contact or injection drug use. Worldwide, it is most commonly spread to infants by their infected mothers. More than half of people who are infected do not show signs of the disease. Each year, approximately 4,000 to 5,000 children are infected with HBV in the United States. The younger the person is when they catch the hepatitis, the more likely it is that he or she will develop chronic liver disease or liver cancer. Approximately 90% of infants, who are infected from their mothers at birth, and between 30 and 50% of those infected before age five, become chronic HBV carriers. This is why hepatitis B immunizations are recommended routinely starting at birth.
Hepatitis A : This infection is caused by the hepatitis A virus (HAV), which is most commonly spread in stool, although it can be spread through contact with infected blood. Infection is transmitted from person to person in households and extended family settings. Adolescents and adults are more likely than young children to develop signs and symptoms of disease. It usually lasts less than two months. However, 10% to 15% of those infected will have prolonged or relapsing disease lasting as long as six months. Fortunately, unlike hepatitis B, chronic hepatitis A disease does not occur. Each year in the U.S., 125,000 to 200,000 people become sick with hepatitis A. Since most infected pre-school children show no symptoms of hepatitis A infection, they often unknowingly spread the hepatitis A virus to others. Prior to the introduction of hepatitis A vaccine, about one-third of the hepatitis A cases in the U.S. occurred in children 5 to 14 years of age.
Haemophilus influenzae type b (H. flu) : This is a bacterium that can infect the lining of the brain causing meningitis. It is transmitted from person to person by coughing or sneezing and invasive disease occurs most often at three months to three years of age, peaking at six to seven months. It is rare after age five years. H. flu can cause a wide variety of serious infections, including pneumonia, severe throat swelling that makes breathing difficult (epiglottitis), and infections of blood, bones, joints, and the covering of the heart. Complications of H. flu meningitis include blindness, deafness, mental retardation, learning disabilities, and death. About 5% of children (500 out of every 10,000) with H. flu meningitis die despite antibiotic treatment.
Streptococcus pneumoniae : These are a group of bacteria also known as pneumococci. They live in the nose and throats of people of all ages and can infect many places including the middle ear (otitis media), sinuses (sinusitis), lungs (pneumonia), the central nervous system (meningitis), and blood stream (bacteremia). Serious pneumococcal infections are most common in infants, toddlers, smokers, and the elderly.
Other early childhood vaccines protect against measles, mumps, German measles (rubella), chicken pox (varicella), and polio. As discussed below, most schools require these vaccines.
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