As of now, BA.4 and BA.5 subvariants of Omicron are not thought to be lethal and compared to the Delta variant of COVID, is said to be milder and more manageable. However, given its ability to evade both natural and vaccine-induced immunity, it is said to spread more easily and efficiently.
A recent South African study found that people who had been previously infected with Omicron but not vaccinated developed nearly eightfold drop in neutralizing antibodies when exposed to BA.4 and BA.5. Simultaneously, people who had been vaccinated and previously infected experienced milder symptoms.
Since many countries have lifted all restrictions and mask mandates, it has become all the more easy for the subvariants to spread.