A homologous booster shot involves the administration of the same vaccine as previously administered, while a heterologous booster shot involves the administration of a different vaccine.
[citation needed] "Heterologous prime-boost immunization is administration of two different vectors or delivery systems expressing the same or overlapping antigenic inserts.
"[1]"An effective vaccine usually requires more than one time immunization in the form of prime-boost.
Traditionally the same vaccines are given multiple times as homologous boosts.
New findings suggested that prime-boost can be done with different types of vaccines containing the same antigens.