Would it do any better against contamination than the orange suits of "The Naked Time"? The hood doesn't appear hermetically sealed in this case, either.
The vest does have the look of a radiation protection system based on absorption of radiation by "armor plates" covering key body locations... But it wouldn't do much good against contamination. Okay, perhaps it is easier to wash than the regular uniform, but in order to be of help, it would need to cover the entire uniform.
In any case, too bad that this sort of diversity was lost later in the show.