Introduction

One of the most dramatic advances of medicine has been the development and use of vaccines for the prevention of once common childhood diseases. Over the past 25 years, mass vaccination programs have resulted in 98% or more declines in the incidences of measles, mumps, rubella, diphtheria and polio. An intense worldwide vaccination program has resulted in the global eradication of smallpox. It is expected that measles will be eliminated as an indigenous disease in the continental United States by 1990. Continued research and development of new vaccines is necessary to combat emerging new pathogens (e.g., the HIV virus). In some cases, such as with the pneumococcal, influenza and hepatitis B vaccines, lack of public awareness and acceptance has limited the effectiveness of the vaccination programs. Immunization programs continue to be cost-effective methods of preventing illness. In 1984, an estimated $1 billion was saved as a result of the polio vaccine, and $500 million was saved through use of the measles vaccine. Vaccine development and public vaccination programs are vital to our national disease prevention efforts.

Prevalence

Measles

There were 2,587 cases of measles reported in 1984. However, in 1984, 94% of the Nation's counties reported no measles at all, and 75% of the cases occurred in just six states.

Mumps

In 1984, 3,021 cases of mumps were reported, the lowest number a cases reported since mumps became a nationally notifiable disease in 1968.

Children aged 5-14 years had the highest incidence of mumps in 1983, accounting for 60% of the cases reported with known age for that year.

Rubella

The 752 cases of rubella reported in 1984 were the fewest reported cases since rubella became a nationally notifiable disease in 1966.

Children aged 0-4 have the highest incidence of rubella (1.8 cases/100,000 population) and accounted for one-third of all cases reported in 1983.

In 1984, five cases of congenital rubella syndrome were reported in the United States.

Diphtheria

Only one case of diphtheria was reported in the United States during 1984.

Pertussis

There were 2,276 cases of pertussis reported in 1984. For the decade 1974 to 1984, the annual number of pertussis cases reported ranged from 1,000 to 2,500, with an average of 1,813 cases per year.

Between 1982 and 1983, 43% of patients with pertussis were less than 6 months old. Of the patients with pertussis less than 1 year old, 73% were hospitalized, 22% had pneumonia, 2% had 1 or more seizures and 0.7% died.

Tetanus

In 1984, 74 cases of tetanus were reported in the U.S. the lowest number ever reported.

57% of the 91 persons reported with tetanus in 1983 were 60 years of age or older.

In 6% of tetanus cases in 1982 and 1983, no wound or other condition could be implicated. Nonacute skin lesions such as ulcers or abscesses were reported in 17% of tetanus cases during those years.

Polio

Eight cases of poliomyelitis were reported in the United States during 1984.

Of the 89 cases of paralytic poliomyelitis reported from 1977 to 1983, 77% were endemic, 11% epidemic, 6% imported and 7% immune-deficiency related. 87% of the endemic cases were among vaccinees or contacts of vaccine recipients.

Childhood Vaccination

The World Health Organization is focusing its immunization program on the following six vaccine-preventable diseases which in 1983 were killing 5 million children per year in developing countries (10 per minute) and disabling an equal number: diphtheria, pertussis, tetanus, measles, poliomyelitis and tuberculosis.

Hepatitis B

In 1983, for the first time, hepatitis B was the most commonly reported cause of viral hepatitis accounting for 24,318 (43%) of the 56,469 reported cases.

There were 10.4 cases of hepatitis B per 100,000 population in 1983. Persons aged 30-34 accounted for 65.6% of cases of hepatitis B, males accounted for 61.1% and whites accounted for 65.4%.

Influenza

The incidence of influenza is difficult to judge; however, it is estimated that during the winter of 1983-84, 50,000 Americans died as a result of influenza.

Meningococcal Infections

There were 2,736 reported cases of meningococcal infections in the U.S. in 1983. 52% of the reported meningococcal infections affected children under 5 years of age.

Haemophilus Influenzae Type b Infections

H. influenzae b (Hib) is the most common cause of bacterial meningitis accounting for 12,000 cases annually. The mortality rate for H. influenzae b meningitis is 5%.

In addition to being the most common causes of bacterial meningitis in the U.S., Hib also causes epiglottitis, sepsis, cellulitis, septic arthritis, osteomyelitis, pericarditis and pneumonia. By 5 years of age one of every 20 children in the U.S. will have had a systemic infection due to Hib.

Pneumococcal Infections

Estimates of the incidence of pneumococcal infections range from 150,000 to 570,000 cases per year including 16,000 to 55,000 cases of pneumococcal bacteria and 2000 to 6200 cases of pneumococcal meningitis.

Public Awareness

A 1978 survey prepared for the Centers for Disease Control (CDC) revealed that 54% of respondents felt immunizations in general are very safe, and 36% felt immunizations are moderately safe. However, differences were evident among the following groups.

Percent Respondents Stating that Vaccinations Are Very Safe

• High Income 60%
• College Graduate 65%
• White 55%
• Low Income 49%
• Less than H.S 54%
• Black 44%

If a nationwide immunization program were started against a disease such as polio, 79% of adults would want to be immunized, according to the 1978 CDC survey on immunization attitudes. However, attitudes differed among the following groups.

Percent of Respondents Wanting Immunization If A Nationwide Program Were Started Against A Disease Such As Polio

• High Income 85
• Low Income 69
• College Graduate 88
• Less than H.S 70
• Adults with Children 88
• Adults without Children 72

Service Delivery

Vaccine Licensure

Vaccines were licensed for use in the United States on the following dates:

• Rabies—1915 (rabbit brain); 1956 (duck embryo)
• Plague—1942
• Pertussis—1914
• Diphtheria—1927
• Tetanus—1933
• Influenza—1945
• Diphtheria; tetanus; pertussis—1949
• Poliomyelitis—1955 (inactivated)
• Poliomyelitis, oral; Type I—1961; Type II—1961; Type III—1962
• Measles; Live—1963; Killed—1963
• Mumps—1967
• Rubella—1969
• Hepatitis B—1981
• Meningococal—1974
• Pneumoccal—1977
• Hemophilus influenza-b—1985

The incidence of rubella declined by 70% between 1982 and 1983 for persons ages 15 years or older as a result of intensified vaccination efforts aimed especially at susceptible postpubetal females.

All 50 states have laws requiring proof of immunization for entrance into grade school. Official immunization records exist in all 50 States.

An estimated 5-15% of college-aged individuals in the United States are susceptible to infection from measles.

A 1984 survey of the Nation's 3,600 colleges showed that 16% had requirements for measles and/or rubella immunity as a condition of attendance. 13 states require premarital testing for rubella.

There are federally-funded programs to educate mothers of newborns of immunization schedules in 44 of 52 reporting areas (the reporting areas include the 50 states, Washington, D.C., and New York City).

In 1984, an estimated 22.2% of those age 65 and older (a high-risk group) received the influenza vaccine, and 9.8% of that age group received the pneumococcal vaccine.

An estimated 80% of those at greatest risk of hepatitis B are not receiving the vaccine.

Serosurvey results show that 49%-60% of persons 60 years of age or older (who account for 57% of tetanus cases) have inadequate levels of circulating antitoxin.

State and territorial health agencies spent an estimated $33 million in 1983 for immunization programs.

Cost Effectiveness

The benefit-cost ratio of the combined rubella and measles vaccine is estimated to be over 14:1, and 10.3:1 for the polio immunization. This translates to an estimated savings of about $1 billion per year for polio and $500 million per year for measles.

Since 1963, over 59 million cases of measles and 19,500 cases of mental retardation have been averted, and 5,900 children's lives have been saved as a result of measles immunization.

Adverse Events

A survey from 1979 through 1982 in the Monitoring System for Adverse Events Following Immunization showed that the most frequently reported adverse event associated with receipt of vaccine was fever (59% of all reports) followed by local reactions (36%). 26% of reports were for adverse events other than fever, local reactions or rash.

Of the major illnesses temporarily associated with vaccinations reported to the CDC, death from sudden infant death syndrome (SIDS), convulsions and encephalitis all occurred less frequently after the DTP vaccinations than would be expected by chance alone.

In 1976 there was an increased risk of Guillain-Barre Syndrome (GBS) following the A/New Jersey influenza vaccine, but in subsequent years there has been no increased risk of GBS following influenza vaccines.

Significant Trends

Measles

There has been a 99.6% reduction in measles cases from the pre-vaccine era when from 1950 to 1962, an annual average of 525,730 cases were reported, as compared to 1981 to 1984, when an average of 1,915 cases per year were reported.

Mumps

There has been a 98.1% decline in the number of reported cases of mumps from 1968, (the year after licensure of the mumps vaccine) to 1984.

Rubella

Since the rubella vaccine became available in 1969 there has been a 98.7% decline in reported cases to an all time low of 745 cases in 1984.

Diphtheria

From 1980 to 1984, 5 or fewer cases of diphtheria were reported per year. In 1921, there were 206,939 reported cases of diphtheria, resulting in a death-to-case ratio of 7.5 percent.

Pertussis

The incidence of pertussis has declined 98.4% since the introduction of the vaccine:

Average Number of Cases Per Year—1945-1950—110,847; 1974-1984—1,813

Tetanus

From 1976 to 1984, the incidence of tetanus remained stable, ranging from 64 to 95 annual cases and averaging 82 cases per year. No national incidence records were kept for tetanus when the vaccine became available in 1933. In the first year that tetanus was nationally reported (1947), 560 cases were recorded.

Poliomyelitis

From 1974 to 1984, an average of 11 cases of paralytic poliomyelitis were reported each year. Prior to introduction of the first polio vaccine in 1955, in excess of 15,000 cases per year were being reported.

Meningococcal Infections

The meningococcal infection rate between 1974 and 1983 increased from 0.64 to 1.17 cases per 100,000 population.

Hepatitis B

From 1974 to 1983 the hepatitis B infection rate doubled from 5.15 to 10.39 cases per 100,000 population.

Special Issues

Elimination of Measles

Since 94% of all counties of the U.S. reported no cases of measles in 1984 and since 75% of the measles cases that year were from just six states, the elimination of indigenous measles is likely to occur in this country by the year 1990.

New Vaccines

In April of 1985, a vaccine against H. influenza b infections (the most common cause of meningitis) was approved by the FDA. The American Academy of Pediatrics now recommends this vaccine for children 2 years old.

New vaccine development is a major medical research priority. Vaccines for the following illnesses have advanced to the stage of clinical trials:

• Meningitis (streptococcal),
• Pertussis,
• Gonorrhea (tested but none found promising),
• Influenza (a live vaccine),
• Diarrheal illness (cholera, typhoid, shigella, roto-virsus),
• Hepatitis, Chicken pox, and Malaria.

Rising Vaccine Costs

A manufacturer of the diphtheria, pertussis and tetanus (DPT) vaccine announced in May 1986 that it would continue to supply the DPT vaccine but will nearly triple its price to combat rising liability problems.

It is estimated that before 1990 the cost of the required vaccines to fully immunize one child in the U.S. may reach $100 or more.

Adult Immunizations

Poor public awareness and lack of acceptance of the hepatitis B, influenza and pneumococcal vaccines limit their effectiveness.

The Advisory Committee on Immunization Practices of the Centers for Disease Control recommends that the pertussis vaccine not be given to persons over seven years of age, infants with underlying neurologic diseases, or infants with seizures within three days of receipt of the DTP vaccine or encephalophathy within seven days of receipt of the DTP vaccine.

Steven Parker

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