The Biden administration is planning to announce that most Americans who have received the coronavirus vaccine will need booster shots to combat waning immunity and the highly transmissible delta variant that is sparking a surge in covid-19 cases, according to four people familiar with the decision. The administration’s health and science experts are coalescing around the view that people will need the boosters eight months after being fully vaccinated, according to the people, who spoke on the condition of anonymity to discuss a decision not yet public. The move is likely to be announced as soon as this week. Administration...