Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Vaccine

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infected individuals to fend off further illness by stimulating

components of the immune system; others have genetically

engineered a protein on the surface of HIVto prompt immune

response against the virus; and yet others attempted to protect

uninfected individuals. The challenges in developing a protec-

tive vaccine include the fact that HIV appears to have multiple

viral strains and mutates quickly.

In January 1999, a promising study was reported in

Science magazine of a new AIDS vaccine created by injecting

a healthy cell with DNA from a protein in the AIDS virus that

is involved in the infection process. This cell was then injected

with genetic material from cells involved in the immune

response. Once injected into the individual, this vaccine

“catches the AIDS virus in the act,” exposing it to the immune

system and triggering an immune response. This discovery

offers considerable hope for development of an effective vac-

cine. As of June 2002, a proven vaccine for AIDS had not yet

been proven in clinical trials.

Stimulating the immune system is also considered key

by many researchers seeking a vaccine for cancer. Currently

numerous clinical trials for cancer vaccines are in progress,

with researchers developing experimental vaccines against

cancer of the breast, colon, and lung, among other areas.

Promising studies of vaccines made from the patient’s own

tumor cells and genetically engineered vaccines have been

reported. Other experimental techniques attempt to penetrate

the body in ways that could stimulate vigorous immune

responses. These include using bacteria or viruses, both

known to be efficient travelers in the body, as carriers of vac-

cine antigens. Such bacteria or viruses would be treated or

engineered to make them incapable of causing illness.

Current research also focuses on developing better vac-

cines. The Children’s Vaccine Initiative, supported by the

World Health Organization, the United Nation’s Children’s

Fund, and other organizations, are working diligently to make

vaccines easier to distribute in developing countries. Although

more than 80% of the world’s children were immunized by

1990, no new vaccines have been introduced extensively since

then. More than four million people, mostly children, die

needlessly every year from preventable diseases. Annually,

measles kills 1.1 million children worldwide; whooping cough

(pertussis) kills 350,000; hepatitis B 800,000; Haemophilus

influenzae type b (Hib) 500,000; tetanus 500,000; rubella

300,000; and yellow fever 30,000. Another 8 million die from

diseases for which vaccines are still being developed. These

include pneumococcal pneumonia(1.2 million); acute respira-

tory virus infections (400,000), malaria (2 million); AIDS (2.3

million); and rotavirus (800,000). In August, 1998, the Food

and Drug Administration approved the first vaccine to prevent

rotavirus—a severe diarrhea and vomiting infection.

The measles epidemic of 1989 was a graphic display of

the failure of many Americans to be properly immunized. A

total of 18,000 people were infected, including 41 children

who died after developing measles, an infectious, viral illness

whose complications include pneumonia and encephalitis. The

epidemic was particularly troubling because an effective, safe

vaccine against measles has been widely distributed in the

United States since the late 1960s. By 1991, the number of

new measles cases had started to decrease, but health officials

warned that measles remained a threat.

This outbreak reflected the limited reach of vaccination

programs. Only 15% of the children between the ages of 16

and 59 months who developed measles between 1989 and

1991 had received the recommended measles vaccination. In

many cases parent’s erroneously reasoned that they could

avoid even the minimal risk of vaccine side effects “because

all other children were vaccinated.”

Nearly all children are immunized properly by the time

they start school. However, very young children are far less

likely to receive the proper vaccinations. Problems behind the

lack of immunization range from the limited health care

received by many Americans to the increasing cost of vacci-

nations. Health experts also contend that keeping up with a

vaccine schedule, which requires repeated visits, may be too

challenging for Americans who do not have a regular doctor or

health provider.

Internationally, the challenge of vaccinating large num-

bers of people has also proven to be immense. Also, the reluc-

tance of some parents to vaccinate their children due to

potential side effects has limited vaccination use. Parents in

Vaccines stimulate the production of antibodies that provide immunity

from disease.

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