The group of individuals affected are among those at higher risk of severe illness if they get Covid-19 and are therefore likely to benefit from a booster vaccination.
Mae’r grŵp o unigolion yr effeithir arnynt ymysg y rhai sy’n wynebu risg uwch o ddatblygu salwch difrifol os byddant yn cael Covid-19, felly maent yn debygol o elwa ar bigiad atgyfnerthu.