Lecture 15

Vaccines

History

• 1717- Turkey- smallpox from sick person into veins of well person

• Variolation- mortality rate- 1%

• Edward Jenner received this treatment at age of 8

Edward Jenner

• Observed milkmaids who became infected with cowpox, did not get smallpox

• Experiments- inoculated people with cowpox in order to prevent smallpox infection

• Vaccination: Vacca=cow

• Vaccine=

• Smallpox eliminated worldwide

Vaccines

• Prevention can control many communicable diseases

• Bacterial diseases can often be treated with antibiotics, if prevention fails

• Viral diseases, not easily treated

• Vaccination only feasible means of controlling viral diseases

• Herd immunity=

Types of Vaccines

1. Live attenuated vaccines

2. Inactivated vaccines

3. Toxoid vaccines

4. Subunit vaccines

5. Conjugate vaccines

6. DNA vaccines

7. Recombinant vector vaccines

Attenuated whole-agent vaccine

• Use living, but weakened microbes

• More closely mimic an actual infection

• generally life-long immunity

• 95% effective for many vaccines

Inactivated whole-agent vaccine

• Use microbes that have been killed

• Still provokes immune response

Toxoid vaccine

• Inactivated toxins

• Remember- toxins are produced by some bacteria and these are what cause the disease

Subunit vaccine

• Use only the part of the antigen that stimulates a strong immune response

• Safer- can not reproduce in the recipient

• Also, little or no extraneous material, and therefore less side effects

Conjugate vaccine

• Some types of vaccines use polysaccharides

• Child’s immune system do not respond well to polysaccharides until 15-24 months

• Polysaccharides combined with another protein to make vaccine

Nucleic acid vaccines

• Depend on ability of some cells to:

– take up and translate foreign DNA

– display the resulting proteins, inducing a strong immune response

• One has been approved for humans

Development of new vaccines

• Vaccines most desirable method of disease control

• Early successful vaccines cultured in animals• With cell culture- could make vaccines that

would not grow on anything but human cells• Some vaccines do not need cell culture-

recombinant vaccines and DNA vaccines• Plant potential source for vaccines• In future- possibility for vaccines to treat

addiction, Alzheimer's, disease and cancer

Safety of vaccines

• Sometimes possibly to cause the disease while trying to prevent it

• Risk considered worthwhile

• Public reactions to such risks has changed

• Some believe connection between autism and MMR vaccine

• No studies have shown evidence of this