Question

Suggest why most vaccines have to be given by injection.

Answer 1

Oral vaccines are generally given for Enteric diseases like polio, cholera, rotavirus etc., where the pathogens are food/water borne and enter body through oral route. Most of the other vaccines are injectables and a few flu vaccines are nasal sprays to mimic the original route of infection. Oral polio vaccine contains live weakened virus which may revert to virulent form and cause disease. So it is being replaced by injectable polio vaccine. Injectable vaccines are safer and slightly less effective compared to it's oral version. Not all vaccines can be oral and most can only be injectable.

Answer 2

Because it should goes in our cell organ