ATLANTA - Vaccination has played an important role in our nation's fight against infectious diseases, said the Centers for Disease Control and Prevention (CDC), which issued a report highlighting the 10 greatest public health achievements in the United States. Vaccination led the list.
"Vaccines are the most powerful tools we have to prevent serious infectious diseases and their consequences," said Bruce G. Gellin, MD, MPH, staff director of the Vaccine Initiative, an independent source of vaccine information.
Overall, U.S. vaccination coverage is at record highs, but it is important not to become too complacent. "On this silver cloud is a black lining. In some ways, immunization has become a victim of its own success," said Gellin, who spoke recently at a press conference in Washington, D.C., sponsored by the National Foundation for Infectious Diseases.
In 1997, coverage among children 19 to 35 months exceeded 90% for three or more doses each of four vaccines, diphtheria-tetanus-pertussis vaccine/acellular pertussis (DTP/DTaP), poliovirus vaccine and Haemophilus influenzae type b (Hib) vaccine, and one or more doses of measles-containing vaccine.
Coverage with four doses of DTP was 81% and with three doses of hepatitis B (HepB) vaccine was 84%. Coverage was lower for varicella vaccine (26%), which was licensed in 1995, and for the combined series of four DTP/three polio/one measles/three Hib (76%). Coverage for the new rotavirus vaccine, licensed in December, has not yet been measured.
Coverage among children 5 to 6 years of age has exceeded 95% each school year since 1980 for DTP, polio and measles-mumps-rubella (MMR) vaccines, according to the CDC.
Because of this, dramatic declines in morbidity have been seen for most vaccine-preventable diseases that are part of the routine childhood immunization schedule. These include DTP, MMR, polio and Hib. Wild poliovirus was declared eradicated in 1991 in the Western Hemisphere due to vaccination; the other seven diseases have seen declines of nearly 100% in the United States.
One of humankind's greatest medical achievements has been the eradication of smallpox through an international vaccination campaign. The eradication of smallpox in 1977 enabled the United States to discontinue routine vaccination in this country and save the cost of vaccination against and treatment of this horrible disease. This cost has been recouped many times over.
It seems an ounce of prevention is cheaper than a pound of cure. In 1994, every dollar spent to administer oral poliovirus vaccine (OPV) and measles vaccine saved $13.70 in direct medical costs and $5.94 in indirect societal costs, according to the report.
During 1951-1954, an average of 16,316 paralytic polio cases and 1,879 polio deaths were reported each year. Today, all U.S. cases have been linked to importations or the vaccine. A change in the routine immunization schedule that calls for inactivated polio vaccine (IPV) for the first two doses is expected to reduce the number of vaccine-associated polio cases, which average about eight cases per year.
Measles vaccine was licensed in 1963. Prior to that, an average of 503,282 cases and about 432 measles-related deaths occurred each year. Cases began to decline in 1965, but there were three epidemics in 1970-1972, 1976-1978 and 1989-1991. Children from 4 to 6 years now receive a booster before school entry. Today, measles has reached a record low of 89 cases. These cases appear to be associated with international importations, according to the CDC.
In less than a decade, the use of the Hib conjugate vaccines has nearly eliminated Hib invasive disease among children. Before the first vaccine was licensed in 1985, an estimated 20,000 cases of Hib invasive disease occurred each year. In 1998, 54 cases of Hib and 71 cases of H. influenzae non-typeable invasive disease among young children were provisionally reported.
"I think this is part of a story that really needs to be told better," Gellin said. "This was the most severe bacterial infection in childhood; about 5,000 cases became meningitis, 2,000 to 3,000 deaths every year. Last year in the United States, there were 54 cases." Gellin said the study of meningitis in children has become grand rounds material. "Elder pediatricians are concerned that the people coming up in medical centers are not learning about meningitis any longer because this disease has been largely eliminated."
Despite these remarkable successes, several challenges face the U.S. vaccine-delivery system. About 11,000 U.S. children are born everyday, each requiring 15-19 doses of vaccine by 18 months of age. In addition, the approval of new vaccines are anticipated against pneumococcal and meningococcal infections, influenza, parainfluenza, respiratory syncytial virus (RSV), and chronic diseases and rheumatic heart disease that occurs as a sequela of group A streptococcal infection. Clinical trials are also being conducted for vaccines to prevent HIV. These will need a place in the immunization schedule, and as more vaccines are added to the schedule, it becomes more complex.
Maintaining high vaccination rates in this country will take a unified effort. Health care providers must be aware of the latest developments and recommendations and must pass that information onto parents. Parents must recognize that vaccines protect their children against disease and seek vaccines for their children. Vaccine supplies and financing must remain secure, especially for new vaccines, and researchers must address complex questions about safety, efficacy and vaccine delivery and pursue new approaches to vaccine administration more aggressively. Furthermore, information technology to support timely vaccinations must be made more effective.
Outreach efforts must be made for hard-to-vaccinate populations, such as adolescents and adults. Vaccinating these groups protect not only themselves, but children. Each year, thousands of cases of potentially preventable influenza, pneumococcal disease and hepatitis B occur in these populations. Incidentally, have you received your hepatitis B vaccine? Did you have an influenza vaccination last season?
Some parts of the world, particularly developing countries, are not as successful in vaccinating their young people. Diseases, such as measles, persist in these countries and are imported into the United States. This is one reason why the United States contributes to the vaccination efforts of other countries.
Along this vein, world health officials are trying to eradicate polio by the end of 2000. Worldwide efforts to control measles, which causes approximately 1 million deaths each year, and to expand rubella vaccination programs also are under way. The use of existing vaccines in routine childhood vaccination programs worldwide needs to be expanded, and newer vaccines need to be introduced into the developing world on a routine basis. According to the CDC, the United States would benefit from these efforts by decreasing disease importations from developing countries.
For more information:
- CDC. Ten Great public health achievements - United States, 1900-1999. MMWR. 1999;48:241-243.
- CDC. Impact of vaccines universally recommended for children - United States, 1990-1998. MMWR. 1999;48:243-248.
- Fenner F, Henderson DA, Arita I, Jezek Z, Ladnyi ID. Smallpox and its eradication. Geneva, Switzerland: World Health Organization, 1988.
- Plotkin SA, Orenstein WA. Vaccines. 3rd ed. Philadelphia, Pennsylvania: WB Saunders Co., 1999.
- CDC. Recommended childhood immunization schedule - United States, 1999. MMWR. 1999;48:12-6.
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