Er bod lefel uchel o imiwnedd wedi datblygu yn y boblogaeth dros y ddwy flynedd a hanner ddiwethaf, mae'r risg o gael COVID-19 difrifol yn parhau i fod yn anghymesur o uchel i grwpiau oedran hŷn, preswylwyr cartrefi gofal i oedolion hŷn, a phobl â chyflyrau iechyd penodol sy’n bodoli eisoes. Mae ansicrwydd yn parhau hefyd ynghylch esblygiad y feirws, parhad ac ehangder yr imiwnedd, ac epidemioleg yr haint.
Whilst there is high level of strong population immunity developed over the past two and a half years, the risk of severe COVID-19 continues to be disproportionately greater in those from older age groups, residents in care homes for older adults, and persons with certain underlying health conditions. There also still remains on-going uncertainty regarding virus evolution, the durability and breadth of immunity, and the epidemiology of infection