Live attenuated vaccines induce humoral/antibody-mediated and cell-mediated components of the immune system. They do this via activation of T and B cells. T cells become activated when the live virus is inoculated into the host and enters various cell types. The associated proteins are proteolysed within the cell and presented via MHC-I to circulating T-cells. B cells become activated when circulating dendritic cells phagocytose the viral vaccine and present the antigens via MHC-II to plasma cells, leading to their maturation into memory B-cells.
Theoretically, live attenuated vaccines could revert to their virulent form, causing infectious symptoms in the host. Immunocompromised patients are especially susceptible to this. Currently, the only live attenuated vaccine known to actually do this is the oral polio (Sabin) vaccine.
Live attenuated vaccines generally do not require boosters as they induce memory B-cells to produce circulating antibodies, providing a much longer-lasting immunity.
The Varicella zoster virus (VZV) vaccine for chickenpox is a live attenuated vaccine often given to children.
There are currently two vaccines for shingles - Zostavax and Shingrix. The older one, Zostavax, is a live attenuated vaccine and can be given to healthy adults over age 60 to prevent shingles. Zostavax is contraindicated in immunosuppressed patients. The newer one, Shingrix, is much more effective and is a recombinant vaccine indicated for adults over age 50 regardless of whether they had chickenpox.
The Sabin polio vaccine is a live-attenuated virus. It was administered orally but is no longer available in the United States.
The vaccine for smallpox is a live-attenuated vaccine. It is not routinely administered.
The vaccine for yellow fever is a live-attenuated vaccine.
The intranasal influenza vaccine is a live-attenuated vaccine.
The vaccine for measles, mumps, and rubella (MMR) is a live-attenuated vaccine. It is the only live attenuated vaccine that can be given to AIDS patients given its safety profile.
The vaccine for rotavirus is a live attenuated vaccine. It is unique in that it is first given at 6 weeks of age when most live attenuated vaccines are not given until 9 months of age.
There are several vaccines for typhoid fever, caused by Salmonella typhi. The oral vaccine (Ty21a) is a live attenuated vaccine.
Previously used for tuberculosis, the BCG vaccine is no longer administered for this purpose. Instead, it is used in certain urological malignancy treatments.
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