Adequate serum levels of selenium are important too.
https://www.liverdoctor.com/selenium-helps-body-fight-viruses/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6769590/
The food we eat and has been factory farmed generally has been stripped of the micronutrients we need.
Zinc, copper, selenium, manganese, magnesium are all important to the immune system.
So is Vit D and Vit C.
The "RDA" on most multivitamins is the "minimum", most people can safely consume far more than the RDA.
I advise my children away at college to have at least 200% of the RDA of key nutrients, and to supplement more if they are feeling run down.