"BA.4 and BA.5 sub-variants are easily transmissible, have the ability to avoid immunity, attack the lungs of patients and have a tendency to cause more serious symptoms than the original Omicron variant."
https://www.thaipbsworld.com/over-80-covid-19-ba-4-and-ba-5-sub-variant-cases-found-in-thailand-to-date/
However there is conflicting information saying it's not more severe:
"The increasing prevalence of Omicron BA.4 and BA.5 is likely to be a factor in the recent increase in cases seen in the UK and elsewhere, though there is currently no evidence that Omicron BA.4 and BA.5 cause more severe illness than previous variants."
https://www.gov.uk/government/news/covid-19-variants-identified-in-the-uk-latest-updates
Either way it's good to keep updated and boosted with ones vaccines if possible.
Be safe.