Attenuated (Live) Vaccines 

Attenuated Vaccines 

Inactive (Killed) Vaccines

Toxoid Vaccines 

Combination Vaccines 

Vaccines that contain live virulent microbes.

The most common method for attenuating viruses invloves raising them for numerous generations in tissue culture cells until the viruses lose the ability to produce disease.

Bacteria may be made avirulent by culturing them under unusual conditions or by using genetic manipulation. 

those containing attenuated microbes-are alos called modified live vaccines. 

They contain active but avirulent organisms or viruses, these vaccines conditions.

These vaccines infect host cells and replicate; the infected cells then process endogenous viral antigens.

Viral vaccines trigger a cell mediated immune response dominated by type 1 helper T cells and cytotoxic T cells  

Although usually very effective, attenuated vaccines can be hazardous because modified microbes ma retain enought residual virulene to cuase disease in immunosuppressed people. 

there are two types: 

* Whole agent vaccines- produced with deactivated but whole microbes

* Subunit Vaccines- produced with antigenic fragments of microbes 

Neither of these can replicate so "booster" doses must be administered to achieve full immunity, and immunized individuals do not stimulate contact immunity 

When microbes are killed for use in vaccines, it is important that their antigens remain as similar to those of living organisms as possible 

It is more efficacious to induce an immune response against toxins than against cellular antigens.