5.2. Vaccine platforms
Mostly, designed vaccines are divided into 6 categories based on their
platform including inactivated or
killed, live attenuated, DNA or RNA, protein subunit, engineered viral
vector and virus-like particle (VLP). From a more generalized
perspective, vaccines require two basic components: the antigen that is
either provided by the vaccine or produced by the expression system of
vaccinated individual, and the non-specific innate immune stimuli, which
are mainly provided by alarmins such as damage-associated molecular
pattern (DAMP) or pathogen associated molecular pattern (PAMP)
molecules. The live attenuated vaccines are the only platform that
deliver both necessaries intrinsically, while the other non-viral
vaccine platforms require artificial alert molecules commonly known as
adjuvants. Furthermore, the non-viral platforms depend primarily on
multiple booster doses to provide desirable protection whereas the live
attenuated vaccines usually make immunity after a single dose of
administration [8]. Like the non-viral vaccines, the inactivated or
killed platforms sometimes require adjuvant and multiple administration
for effective immunization [41].