Table 2.

Benefits and Drawbacks of Immunogens Used in Vaccines (WHO, 2021).

Immunogen	Description	Benefits	Drawbacks	Examples
Inactivated virus	Inactivated dead virus	Triggers powerful antibody response	Needs significant amount of virus and shows low or no cellular response	Influenza, hepatitis A, and rabies
Viral subunit	A pathogen-derived protein	Fewer side effects compared to the whole virus (swelling or redness at the injection site)	Complex process and may be poorly immunogenic	Influenza
Viral vector	Viral pathogen expressed on a safe virus, does not result in disease	Fast development, powerful cellular response, and easier to produce	Prior exposure to vector virus (eg. adenovirus) is likely to lower immunogenicity, certain vectors need boosting with another vector	Ebola
Nucleic acid	mRNA coding for a viral protein	Fast development and powerful cellular immunity	Reduced antibody response	COVID-19