'The worst version' of COVID is spreading. Can we update our vaccines in time? Experts say BA.5 is the one to worry about: “The worst version of the virus that we’ve seen,” as Dr. Eric Topol, the founder of Scripps Research Translational Institute, More symptoms. BA.4 and BA.5 are also better at replicating in lung cells than BA.2 — a shift that could mean, according to one experimental model, that they’re more “pathogenic” as well (i.e., more likely to make you sick). More resistance to treatments. At the same time, BA.4 and BA.5 appear to be 20-fold more resistant than BA.2 to Evusheld — an important monoclonal antibody treatment that has been providing preemptive protection for immunocompromised people. None of this will set the U.S. back to square one. Despite elevated case levels, there are now fewer U.S. COVID patients in intensive care units than there were during previous phases of the pandemic, and the national death rate (about 300-400 per day) is near the all-time low. Acquired immunity, multiple rounds of vaccination and improved treatment options are helping — a lot.