That's interesting.
So, on this thread we have seen that considerable percentages of children in the UK, the US and New Zealand do not get enough vitamin A - and that is before we even talk about how measles infection depletes vitamin A.
It clearly isn't enough to advise that children take a multivitamin and vaguely nod towards vitamin A which 'may' help with measles infection 'but we don't know why'.
Curlew, the link between vitamin A and measles was made in the 1930s.
You may well have been given cod liver oil as a child without that having been particularly to do with measles. Vitamin A isn't only used in the body to fight measles. Vitamin A is important to the immune system in general and is important for many other bodily mechanisms.
en.wikipedia.org/wiki/Vitamin_A
Vitamin A has multiple functions, it is important for growth and development, for the maintenance of the immune system and good vision.[2] Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin the light-absorbing molecule ,[3] that is necessary for both low-light (scotopic vision) and color vision.[4] Vitamin A also functions in a very different role as an irreversibly oxidized form of retinol known as retinoic acid, which is an important hormone-like growth factor for epithelial and other cells.[5]
It was very common in the past to give children cod liver oil for general health. I give it to my children and there is not currently measles circulating in our region. (When measles was circulating a couple of years ago, I spoke to our doctor about upping the dose and about the possibility of giving too much. He didn't know a whole lot about it TBH. I don't live in the UK though - perhaps doctors there are up to speed on vitamin A/measles.)