The FDA has approved an updated covid shot for everyone 6 months old and up, which renews a now-annual quandary for Americans: Get the shot now, with the latest covid outbreak sweeping the country, or hold it in reserve for the winter wave? The new vaccine should provide some protection to everyone. But many healthy people who have already been vaccinated or have immunity because they’ve been exposed to covid enough times may want to wait a few months. Covid has become commonplace. For some, it’s a minor illness with few symptoms. Others are laid up with fever, cough, and fatigue for days or w…