They must be at least three months past any earlier dose of the Covid-19 vaccine and cannot already have had a booster dose during the spring.
Rhaid bod o leiaf tri mis wedi pasio ers iddynt gael unrhyw ddos cynharach o’r brechlyn Covid-19 ac ni ddylent fod wedi cael dos atgyfnerthu eisoes yn ystod rhaglen y gwanwyn.