To reach effective impacts from cancer vaccines, accurate HLA typing is important, but why is HLA typing not required for flu shots, COVID vaccines, or other infectious diseases? Is it due to high demand or any other biological reasons?
The reason to assess HLA type would be to make sure the individual receiving an immune therapy or vaccine can respond to the immunogen at the T cell level. Very small immunogens, such as peptide vaccines or very small protein subunits, may have very few T cell epitopes, which may not elicit T cell responses in some genetic HLA backgrounds, resulting in a weak immune response. Current vaccines are composed of whole organism (killed or attenuated) or fairly large subunits. These vaccine have a relatively large number of T cell epitopes, so genetic non-responders are very low. The one exception I know of is the HBV vaccine, which is composed of the hepatits B virus surface antigen (HBsAg). About 2% of vaccinated people are non-responders and up to 9% are low responders. This can be partly overcome by administering a 4th dose (the regular course of HBV vaccination is 3 doses). The newer HBV vaccine from Dynavax uses a more potent adjuvant and requires only 2 doses and, I believe, has a better rate of protective responses.
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