Download How vaccines work.

How vaccines work.
Prevention of diseases
Your Immune System
• It is always better to prevent a
disease than to treat it after it
occurs.
• Immunity is the body’s way of
preventing/fighting disease.
• Children are born with an
immune system composed of
cells, glands, organs, and fluids
located throughout the body.
• The immune system
recognizes molecules from
germs that enter the body as
"foreign invaders”
(called antigens) and produces
proteins called antibodies to
fight them.
How your Immune system works,
• The first time a child is infected with a specific antigen
(say measles virus), the immune system produces
antibodies designed to fight it.
• This takes time . . . usually the immune system can’t
work fast enough to prevent the antigen from causing
disease, so the child still gets sick.
• However, the immune system “remembers” that
antigen. If it ever enters the body again, even after
many years, the immune system can produce
antibodies fast enough to keep it from causing disease
a second time. This protection is called immunity.
• Let’s watch the immune system at work.
• Vaccines artificially program this system w/o exposure
to the natural version of viruses / bacteria
Types of vaccine
1) Live-attenuated vaccines: Active, but very weak
• Vaccines made when the virus is weakened to such a level
that they reproduce only about 20 times in the body. By
comparison, natural viruses reproduce thousands of times.
• "Live-attenuated vaccines can cause very mild illness in a
small proportion of people," says John Bradley, M.D.,
member of the committee on infectious diseases of the
American Academy of Pediatrics (AAP). "However, these
side effects are usually very mild and limited to a low-grade
fever or runny nose." Dr. Bradley also notes that about 5 to
10 percent of children who receive the varicella
(chickenpox) vaccine develop a few pox spots, but it's
nothing compared to the full-blown illness.
Types of Live-attenuated vaccines
Example/recommended:
• Measles, mumps, rubella (MMR combined
vaccine)
• Varicella (chickenpox)
• Influenza (nasal spray)
• Rotavirus
• Others: Zoster (shingles), Yellow fever
2) Inactivated vaccines:
• The bacteria/virus is completely killed using a
chemical
• Inactive / dead pathogens used
• The strength of these vaccines tend to wear off
over time, resulting in less long-lasting immunity.
So, multiple doses of inactivated vaccines are
usually necessary to provide the best protection.
• Examples: hepatitis A, hepatitis B, poliovirus,
haemophilus influenzae type b (Hib),
meningococcal, pneumococcal and the injected
form of influenza.
3) Subunit Vaccines
• Only the antigens/part of the capsid that best stimulate the immune
system.
• Subunit vaccines can contain anywhere from 1 to 20 or more
antigens/capsids.
• They can grow the microbe in the laboratory and then use chemicals to
break it apart and gather the important antigens/capsids.
• A recombinant subunit vaccine has been made for the hepatitis B virus.
Scientists inserted hepatitis B genes that code for important antigens into
common baker’s yeast. The yeast then produced the antigens, which the
scientists collected and purified for use in the vaccine. Research is
continuing on a recombinant subunit vaccine against hepatitis C virus.
Examples
• Hepatitis B
• Influenza (injection)
• Haemophilus influenza type b (Hib)
• Pertussis (DTaP combined immunization)
• HPV
4) Toxoid Vaccines
• For bacteria that secrete toxins, or harmful chemicals as main
cause of illness.
• Inactivate toxins by treating them with formalin, a solution of
formaldehyde and sterilized water. Such “detoxified” toxins, called
toxoids.
• Immune system receives a vaccine containing a harmless toxoid, it
learns how to fight off the natural toxin. The immune system
produces antibodies that lock onto and block the toxin.
• Example: Diphtheria, tetanus (part of DTaP combined
immunization)
5) Conjugate Vaccines
• Many harmful bacteria have an outer coating of sugar molecules
called polysaccharides
• Polysaccharide coatings disguise a bacterium’s antigens so that the
immature immune systems of infants and younger children can’t
recognize or respond to them.
• Conjugate vaccines, a special type of subunit vaccine, get around
this problem.
• When making a conjugate vaccine, scientists link antigens or toxoids
from a microbe that an infant’s immune system can recognize to
the polysaccharides.
• The linkage helps the immature immune system react to
polysaccharide coatings and defend against the disease-causing
bacterium.
• Haemophilus influenzae type B (Hib)
Pneumococcal
Meningococcal
TED Talk on vaccines