New COVID Omicron Variant Spreads BA.4 and BA.5 Have Become Dominant The most recent subvariants of the Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), BA.4 and BA.5, have caused significant upsurge in new cases and hospitalizations in many countries around the world. Soon after their initial discovery in South Africa, BA.4 and...