Vaccines

Vaccine is a biological preparation to strengthens the body’s immunity against a particular disease

a vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins

Effectiveness

Vaccines do not guarantee complete protection from a disease. Sometimes, this is because the host’s immune system simply does not respond adequately or at all. This may be due to a lowered immunity in general (diabetes, steroid use, HIV infection, age) or because the host’s immune system does not have a B cell capable of generating antibodies to that antigen.

Even if the host develops antibodies, the human immune system is not perfect and in any case the immune system might still not be able to defeat the infection immediately. In this case, the infection will be less severe and heal faster.

The efficacy or performance of the vaccine is dependent on a number of factors:

• the disease itself
• the strain of vaccine
• whether one kept to the timetable for the vaccinations
• some individuals are “non-responders” to certain vaccines, meaning that they do not generate antibodies even after being vaccinated correctly
• other factors such as ethnicity, age, or genetic predisposition.

How Do Vaccines Work?

Vaccination is a way to trigger the body’s immune response without becoming sick. The vaccine contains weak or dead organisms that usually do not cause illness. The body is able to destroy the pathogen in the vaccine and produce memory cells. When the body develops immunity to a specific pathogen, immunization has occurred.

If the body is ever exposed to the same pathogen in the future, the memory cells react quickly without a trial-and-error period. This allows the body to destroy the pathogen efficiently before it can cause illness.

Types of vaccines:

Killed vaccine:

Some vaccines contain killed, but previously virulent, micro-organisms that have been destroyed with chemicals, heat, radioactivity or antibiotics

Examples:

• Influenza vaccine
• Cholera vaccine
• Polio vaccine
• Plague vaccine nodal
• Vaccine hepatitis A
• Rabies vaccine

Attenuated vaccine (disabled):

Some vaccines contain live, attenuated microorganisms. Many of these are live viruses that have been cultivated under conditions that disable their virulent properties, or which use closely related but less dangerous organisms to produce a broad immune response; however, some are bacterial in nature. They typically provoke more durable immunological responses and are the preferred type for healthy adults

Examples:

• Yellow fever vaccine (vaccine virus)
•      Measles vaccine (vaccine virus)
•      Rubella vaccine (vaccine virus)
•      Mumps vaccine (vaccine virus)
•      Vaccine typhoid vaccine (bacterial)

Toxoid (TT):

Toxoid vaccines are made from inactivated toxic compounds that cause illness rather than the micro-organism

Examples:

• Tetanus vaccine (tetanus)
• Diphtheria vaccine

Partial units vaccine (Subunit):

Some units used the partial protein consisting of some organisms to cause an immune response instead of entering organism (whether debilitating or disabled) on the immune system.

Examples:

• human papillomavirus – HPV
• Hepatitis B virus

Vaccines vehicle:

Vaccines may be monovalent (also called univalent) or multivalent (also called polyvalent). A monovalent vaccine is designed to immunize against a single antigen or single microorganism

• Haemophilus influenzae type B vaccine