By Alistair Smout LONDON (Reuters) – COVID-19 cases were rising among the over-55s in England, a study found on Thursday, with increased social contact, waning of booster protection and a more contagious subvariant of Omicron possibly driving an increase in hospitalisations. Prime Minister Boris Johnson in February lifted the last coronavirus restrictions in England and abolished a legal requirement to self-isolate after testing positive for the virus. Johnson took those steps after Omicron peaked at the start of the year without causing a wave of hospitalisations and deaths to overwhelm the h…