COVID-19 vaccinations are at a critical juncture as drugmakers test whether new approaches like combination shots or nasal drops can keep up with a mutating coronavirus — even though it’s not clear if changes are needed. Already there’s public confusion about who should get a second booster now and who can wait. There’s also debate about whether pretty much everyone might need an extra dose in the fall. “I’m very concerned about booster fatigue” causing a loss of confidence in vaccines that still offer very strong protection against COVID-19′s worst outcomes, said Dr. Beth Bell of the Universi…