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How do we know that vaccines work? Vaccination is one of the greatest achievements of medicine and has spared millions of people the effects of devastating diseases. Before vaccines became widely used, infectious diseases killed thousands of children and adults each year in the United States: • Before 1985, Haemophilus Influenzae type b (Hib) caused serious infections in 20,000 children each year, including meningitis (12,000 cases) and pneumonia (7,500 cases).1 In 1998, there were 54 cases of Hib disease.2 • In the 1964-1965 epidemic, there were 12.5 million cases of rubella (German measles).3 Of the 20,000 infants born with congenital rubella syndrome, 11,600 were deaf, 3,580 were blind, and 1,800 were mentally retarded as a result of the infection.3 In 1999, there were 238 cases of rubella and 8 cases of congenital rubella.3 • Before 1963, more than 3 million cases of measles and 500 deaths from measles were reported each year.3 More than 90% of children had measles by age 15.3 In 1999, there were 86 cases of measles. • In 1952, polio paralyzed more than 21,000 people.3 In 1998, there were no cases of polio. • In the early 1940s, there was an average of 175,000 cases of pertussis (whooping cough) per year, resulting in the deaths of 8,000 children annually.3 In 1999, 6,031 cases of pertussis were reported.9 • In the 1920s, there were 100,000 to 200,000 cases of diphtheria
each year and 13,000 people died from the disease.3 In 1998, there
was only one case of diphtheria in the United States. Is it better to be naturally infected rather than vaccinated No. Diseases cause suffering and, in some cases, permanent disability or death. Vaccines protect from the disease without risking the serious adverse effects of that illness. • It is much better to gain immunity from a vaccine. Vaccine-preventable diseases can kill; they can cause permanent disabilities such as paralysis from polio, liver damage or liver cancer from hepatitis B infection, and deafness from meningitis caused by several bacteria (Hib, pneumococci, and meningococci). In addition, brain damage can result from measles, Hib meningitis, or pertussis. If a woman gets rubella while pregnant, her baby could have serious birth defects. • Immunity from a vaccine offers protection against future disease that is similar to immunity acquired from a natural infection. Several doses of a vaccine may be needed for a child to have a full immune response. • For some vaccines (e.g. tetanus and Hib) the vaccine is better at creating immunity than a natural infection would be.3 Because of better hygiene and sanitation, hadn’t diseases already begun to disappear before vaccines were introduced? No, they had not begun to disappear. In the 20th century, infectious diseases began to be better controlled because of improvements in hygiene and sanitation (clean water and pest control). However, the incidence of vaccine-preventable diseases only began to drop dramatically after the vaccines for those diseases were licensed and began to be used in large numbers of children. For example: • There were about 500,000 reported cases and 500 deaths from measles each year before the measles vaccine was licensed in 1963.2 In 1998, only 100 cases were reported in the United States.5 • Before the development and use of the Hib vaccine in 1985, approximately 20,000 infants and young children developed life-threatening forms of this infection (meningitis, pneumonia and epiglottitis). Since the introduction of the initial Hib vaccine and the development of the more effective Hib conjugate vaccine, Hib disease has nearly been eliminated in the United States. In 1998 there were only 54 cases of Hib diseases in the United States.2-4 During an outbreak, aren’t the majority of people who catch a disease those who have been vaccinated? Although vaccines have very high effectiveness rates, they are not completely effective for 100% of the people who receive them. For example, a full series of measles vaccine will protect 99 of 100 children from measles, and polio vaccine will protect 99 of 100 children from polio.2 This means that when there is a disease outbreak, the very small number of people for whom the vaccine was not fully effective may still be able to catch the disease. Because almost all children are immunized, and only few are not, during an outbreak a greater number of cases of a given disease may occur among those who were immunized, but a greater proportion of unimmunized children will develop the disease. The fact remains that those who have not received the vaccine are much more likely to catch the disease. • By way of example, consider an actual measles outbreak in Colorado in December 1994.6 Out of 625 children exposed to the disease, 17 got measles. Of the 625 children, 609 had been vaccinated against measles and 16 had not been vaccinated. Of those 609 who had previously been vaccinated, only 10 (or 1.6%) developed measles. Of the 16 children who were not vaccinated, 7 (or 44%) developed measles. In this outbreak, unimmunized children had a risk of measles 25 times larger than immunized children. If vaccine-preventable diseases have been virtually eliminated from the United States, why do American children need to be vaccinated? Although many of these diseases have the potential to be eliminated, outbreaks of diphtheria, measles, and other vaccine-preventable diseases still occur. • Children who are not vaccinated against measles are up to 35 times more likely than immunized children to catch the disease.7 Ten years ago during a 3 year measles epidemic from 1989 to 1991, state health departments in the United States reported 55,622 measles cases, 11,251 hospitalizations, and 125 deaths.3,8 An investigation has shown that where this epidemic occurred, as few as 50% of preschool-aged children had received the measles vaccine.3 • Without protection from vaccines, the vaccine-preventable diseases that have nearly been eliminated are likely to return. Thousands of children and adults will become sick, some will have long-lasting health problems, and some will die. • Many other countries do not have the same levels of immunization that we have achieved in the United States and they continue to have disease outbreaks. Therefore, we must all remain protected with vaccines because dangerous diseases largely under control in the United States are only a plane ride away. Sources: Recommended books and Web sites on this topic: American Academy of Pediatrics Web site (www.aap.org) Centers for Disease Control and Prevention Web site (www.cdc.gov/nip) Humiston SG and Good C. Vaccinating your child: Questions & answers for the concerned parent. Atlanta: Peachtree Publishers; 2000. Offit PA and Bell LM. Vaccines: What every parent should know, revised edition. New York: IDG Books; 1999. |
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