“Everyone is kind of confused,” he said. The current discontent has deep roots. In April, Pfizer chief executive Albert Bourla said a third coronavirus dose was “likely” to be needed. In late July, Pfizer-BioNTech announced that their vaccine’s efficacy waned over time. Data from Israel confirmed a drop. Then, last month, as the delta variant of the coronavirus surged and the World Health Organization decried the distribution of third shots in wealthy countries while poor countries were lacking first doses, President Biden announced that most Americans could begin getting boosters of the Pfizer and Moderna vaccines Sept. 20 — subject to the government’s regulatory processes, which unfolded in recent days and focused only on Pfizer. Regulators already allowed third shots for the immunocompromised who have received Pfizer or Moderna shots but have not yet made recommendations for all recipients of the Moderna and Johnson & Johnson vaccines.