Vaccines

If nothing else watch this very short video on how different vaccines are made.

Naturally Acquired Immunity is that immunity acquired upon exposure to a specific pathogen or foreign antigen.

Artificially Acquired Immunity is that immunity obtained via vaccination with a killed or live attenuated pathogen.

Vaccine is a preparation of killed or live attenuated pathogen or of specially derived pathogen antigenic determinants that is used to induce an immune response that protects an individual to a subsequent exposure to that pathogen.

Vaccination (immunization) is a means of inducing artifically acquired immunity. The goal of vaccination is to induce antibody or cell-mediated immune responses against a pathogen, without simultaneously inducing disease.



Edward Jenner was the army surgeon who is generally credited with advancing the art of "vaccination". On May 14, 1776, Jenner purposely exposed James Phipps with cowpox virus obtained from dairymaid Sarah Nelmes. Phipps became immune to smallpox as evidenced by survival of several purposeful attempts to infect him with the virus. Benjamin Jesty claims to have done the same thing 20 years prior to Jenner. Actually, the Chinese probably were vaccinating against smallpox hundreds of years before either of these men were born.

After the introduction of the smallpox vaccine in 1778 additional vaccines were introduced such as Rabies 1885, Plague 1897, Diptheria 1923, Pertussis 1926, Tuberculosis and Tetanus 1927 and Yellow fever 1935.

TYPES OF VACCINES

Inactivated Vaccines (killed) are vaccines consisting of an inactivated whole pathogen. Because the pathogen is dead these vaccines are considered very safe. However, they usually require several booster doses of the vaccine to induce sufficient immunity. An example of an inactivated vaccine is the Salk Polio vaccine and the Influenza vaccine.

Live, Attenuated Vaccines are vaccines that are made from a live pathogen that has been weakened so it cannot cause disease. These vaccines actually result in a mild infection, thus inducing a very strong protective immune response. A disadvantage of these vaccines is that they typically cannot be given to immunosuppressed individuals. An example of a live, attenuated vaccine is the oral Sabin Polio vaccine and the smallpox vaccine.

Toxoid Vaccine is a vaccine that is made from an inactivated toxin. Many infectious bacteria produce a toxin that is the cause of disease. Toxoid vaccines are made by treating the toxin chemically or with heat to inactivate it. Examples of toxoid vaccines are Diptheria and Tetanus vaccines.

SECOND GENERATION VACCINES

These vaccines are the result of recombinant DNA techology.

Subunit Vaccines are vaccines developed from well defined antigenic fragments of a pathogen.

Recombinant subunit vaccine are obtained using recombinant DNA techniques. Yeast cells are transfected with DNA which encodes an antigenic determinant of a pathogen. The yeast cells are grown in culture and the recombinant vaccine antigen is purified from the yeast cell culture. An example of this type of vaccine is the Hepatitis B vaccine.

Recombinant vector vaccines are made by inserting pathogen genes that encode protective antigens into a virus that does not cause disease (such as the vaccinia virus) but can express the pathogen genes. Although clinical trials are being done using these vaccines, there are no currently approved recombinant vector vaccines.

Conjugate Vaccine is a vaccine that is specially designed to induce immunity in babies who have an immature immune system. These vaccines consist of a polysaccharide (bacterial surface coat antigen) which is combined with an immunogenic protein that can be recognized by the baby's immune system. An example of this type of vaccine is the Haemophilus influenzae type b (Hib) vaccine.

FUTURE VACCINES

DNA Vaccines are made of a modified form of the pathogens DNA. When this DNA is injected into an individual, the pathogen DNA enters the cells which leads to the expression of the genes in the DNA (pathogen antigens). You can read more about DNA vaccines here.

Edible Vaccines are vaccines in which the pathgen antigens are expressed in edible plants such as potatoes and tomatoes. Read more about edible vaccines here.

VACCINE SIDE EFFECTS

Vaccination can result in side effects. These are typically local side effects including pain, redness, swelling, itching or a small lump at the site of injection.

However, occasionally systemic side effects can occur. These might include headache, fever, muscle aches or rashes. Very occasionally severe side effects might occur such as anaphylaxis shock.