That is, it's easy to find scholarly papers published by doctors which don't add the "about" like:
"Measles vaccine is highly effective, with 1 dose being 93% effective and 2 doses being 97% effective at preventing measles." from "Measles Outbreak — Minnesota April–May 2017" by authors from the Minnesota Department of Health, at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5687591/
"Based on the Centers for Disease Control and Prevention data, one dose of MMR vaccine is 93% effective against MeV, 78% effective against mumps virus (MuV), and 97% effective against rubella." by authors from The Ohio State University at https://www.pnas.org/content/pnas/118/12/e2026153118.full.pd... .
Yes, I already mentioned malnutrition as a known factor.
I asked for substantiation of your statement "insufficient vitamin C being especially bad."
You cited reference doesn't even mention vitamin C.