What is Vaccine ● A modified form of natural antigens ● Host develops B and T memory cells that can act against the natural antigens ● To activate immunological defences ● Exposes immune response to pathogen-derived antigens Herd immunity ● Stops the transmission cycle by preventing host to host spread within population ● Immunizing sufficient number of people ● Immunizing the whole population is not necessary Types of vaccines ● Protein subunit ○ Contains isolated and purified viral proteins ● Virus like particles (VLP) ○ Contains viral proteins that mimic the structure of virus but no genetic material ● DNA-Base/RNA-Base ○ Contains viral genetic materials ○ Provides instructions for making viral proteins ● Non-replicating viral vector ○ Contains viral genetic material packaged inside another harmless virus that cannot copy itself ○ Deactivated ● Replicating Viral Vector ○ Contains Viral genetic materials ○ Inside another harmless virus that can copy itself Types of Whole Virus Vaccine ● Inactivated ○ Contains copies of the virus that have been killed ● Live-Attenuated ○ Contains copies of the virus that have been weakened Smallpox ● Caused by variola virus ○ Poxvirus,DNA genome ● Transmitted person to person through close contact or airborne ● 30% infected died ● Related to animal pox virus ○ Cowpox in cattle ○ Mpox in monkey Variolation ● Earilyies origin ○ Chian 1400s ● Material form smallpox blister introduced to an uninvected person ○ Protected against subsequent natural infection and disease ○ Risk of disease/death following variolation was 1~2% compared to 30% following natural infection ● PRacticed form centuries in part of Asia, Africa and eastern Europe 1721 Lady Mary Wortley ● Observed variolation in present day Turkey ● Brought to Western Europe ● Had daughter inoculated 1716 Onesimus ● Slaved man living in boston ● Received violation as a child in West Africa ● Introduced practice to his enslaver ● Led to use of variolation inBoston during 1721 outbreak ○ 1/40 had died ○ Without 1/7 died 1774 Benjamin Jesty ● English farminer ● Aware that milkmaids seemed to be immune to virulent smallpox disease ● Infected wife and sons with cowpox ○ Years later sons were immune to smallpox also Vaccines are derived from vaccinia ● Vaccination with vaccinia ○ Effective and safer than variolation ■ No risk ■ No side effect ● Jenner’s vaccine vaccine became widely used ● Smallpox declared eradicated in 1980

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