TABLE 2
SOURCE: Alan Uba.
causing paralytic poliomyelitis. A complete switch to
IPV occurred in the United States in January 2000.
The first live, attenuated measles vaccine was li-
censed in 1963, followed by mumps and rubella (Ger-
man measles) vaccines in 1967 and 1969. The
combined measles, mumps, and rubella (MMR) vac-
cine has been available since 1971. In the 1980s, epi-
demics of measles in the United States demonstrated
the importance of immunizing and reimmunizing
against measles. Concerns have been expressed over
a possible link between autism and the measles vac-
cine, and this issue is discussed below under ‘‘Contro-
versy over Vaccination.’’
The first hepatitis B vaccine was licensed in 1981.
In the United States, an attempt at selective immuni-
zation of individuals (e.g., those having contact with
blood or blood products, including health-care work-
ers) with the hepatitis B vaccine did not control the
number of new cases. Universal immunization of in-
fants against hepatitis B with a vaccine began in 1990.
The Haemophilus influenzae type b (HIB) vaccine
was first licensed in 1985. The initial vaccine could
only be used in older children because it did not
evoke protective immunity in younger infants. Unfor-
tunately, most HIB disease occurs in the first two
years of life. Subsequently, a new vaccine was intro-
duced in 1990 that proved extremely effective in early
infancy. By 1998, rates of serious bacterial infection
due to HIB had declined by 99.7 percent since the in-
troduction of the newer HIB vaccine in 1985.
A chicken pox (varicella) vaccine was licensed in- Before the vaccine was available, an estimated
four million cases of chicken pox infection occurred
in the United States each year. While most cases of
natural infection were uncomplicated, chicken pox
was responsible for an estimated eleven thousand
hospitalizations and one hundred deaths per year.
Once the vaccine was available, chicken pox became
the most common vaccine-preventable cause of death
in the United States. Universal immunization with the
chicken pox vaccine began the same year that the vac-
cine was licensed.
The pneumococcal-conjugate vaccine was li-
censed in 2000. Streptococcus pneumoniae (pneumococ-
cus) is a leading cause of serious bacterial infection in
childhood, including pneumonia, bacteremia (bacte-
ria in the blood), and meningitis. Pneumococcus is
also the most common cause of ear infections in chil-
dren.Selected Immunizations
Selected immunizations are directed at high-risk
populations. These populations include: (1) individu-
als with underlying immune system disorders, (2) in-
dividuals with chronic underlying medical conditions
that make them more susceptible to severe infection,
and (3) individuals with increased risk of contracting
infection.Impediments to Vaccination
The success of universal immunization cam-
paigns requires high rates of immunization. Factors
that interfere with the delivery of immunizations in-IMMUNIZATION 203