remarkable success of many vaccines, especially those administered in
childhood, and their impressive safety record, together with the eradication
of smallpox, are regarded among the greatest public health achievements
of the 20th century.
kept by the Centers for Disease Control and Prevention (CDC) since
1912 reveal the number of reported cases of an infectious disease before
and after a vaccine became available.The decrease is remarkable: 100
percent in the case of indigenous poliomyelitis (the last case
in the Americas was in Peru in 1992); over 99 percent in the case of
diphtheria, measles, mumps, and rubella; and over 97 percent
in the case of whooping cough (caused by Bordetella pertussis).
All these agents undergo little antigenic variation (or drift) or none
at all, showing that under virtually ideal conditions, vaccination
can be extraordinarily effective.
one year after the introduction in 1999 of a Neisseria meningitidis
serogroup C conjugate vaccine in the United Kingdom, the incidence
of meningitis was reduced by 92 percent among young children
and by 95 percent among teenagers.
A Salmonella typhi Vi conjugate vaccine (Vi-rEPA) reduced
the incidence of typhoid fever among two-to-four-year-old children
by more than 90 percent. Both findings confirm the remarkable effectiveness
of conjugate vaccines..." "...The
experience with measles in the United States is of interest. From
1912 until 1963, the incidence never dropped below 100,000 cases per
year, and epidemics were common. After the introduction of the first
vaccine in 1963, the number of cases fell to very low levels and remained
so until 1990, when there was an epidemic lasting three years and involving
nearly 28,000 patients, most of whom were adolescents or young adults.
This resurgence was due to inadequate vaccination of these patients
at the age of one to two years in major urban areas. The recognition
that immunity can wane after vaccination led to a two-dose vaccination
schedule, which prevented the transmission of indigenous measles infections
within the United States, Canada, and Finland..." "...Sometimes,
vaccination can fail, indicating that it induced a suboptimal immune
response. The failure to respond or a low level of response to a simple
vaccine, such as the hepatitis B vaccine, can be circumvented
by adding additional helper-T-cell epitopes to the vaccine. In the
case of varicellazoster virus, like other such viruses, which
induce latent infections, a live attenuated vaccine may not eliminate
infection but does prevent chickenpox..." "...In
the United Kingdom in the 1970s, fears that the whole-cell pertussis
vaccine induced brain damage caused vaccination levels to drop to approximately
30 percent. Two subsequent outbreaks of whooping cough caused
more than 30 deaths, and many of the infected children suffered brain
damage.A subsequent review of the evidence failed to substantiate the
association between the vaccine and brain damage..."
oral poliovirus vaccine eradicated poliomyelitis from the Americas,
but in the United States, the vaccine caused about 1 case of paralysis
in a vaccinee or close contact per million doses of the vaccine, as
a result of the reversion of the type 3 virus strain used in the vaccine
to virulence. The CDC Advisory Committee on Immunization Practices
and the American Academy of Pediatrics recommended that only inactivated
poliovirus vaccine be used after January 1, 2000.
there is no firm scientific or clinical evidence that the administration
of any vaccine causes a specific allergy, asthma, autism, multiple
sclerosis, or the sudden infant death syndrome. A widely cited report
claimed an association between vaccination against measles (usually
with measles, mumps, and rubella vaccine) and the subsequent occurrence
of inflammatory bowel disease or autism. At least 10 studies found
no evidence to substantiate such an association..."
1966 the estimated number of cases of smallpox worldwide was
20 million. The last case of endemic smallpox occurred in 1977, and
eradication of the disease was announced in 1980. Poliomyelitis
became the next target for eradication, through the administration
of the oral poliovirus vaccine. This task is more difficult because
the vaccine is heat labile, several doses are required, the vaccine
itself can induce paralysis (although very rarely), and unlike the
case with smallpox, there is no simple test to indicate that vaccination
has been successful. Indigenous poliomyelitis has already been eliminated
from the Americas, Europe, the western Pacific region, and Southeast
Asia, but it will take a few more years to achieve global eradication.
is the most contagious infection of humans and causes 30 percent of
all deaths due to vaccine-preventable diseases. The successful interruption
of the transmission of measles infection in countries with very high
rates of vaccination coverage is indicative of the progress being made
toward the goal of eliminating measles from the Americas.
World Health Organization (WHO) Expanded Programme on Immunization increased
the level of vaccination to control tetanus, diphtheria, whooping cough,
tuberculosis, measles, and poliomyelitis in developing countries from
5 percent in 1974 to an average of 80 percent by the 1980s, and it
has since remained at about that level..."