| Health officials have concluded that Americans who received the coronavirus vaccine will need booster shots to combat waning inoculation 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 move, likely to be announced as soon as this week, would call for people to receive an additional shot eight months after they are fully vaccinated, according to the people, who spoke on the condition of anonymity to discuss a decision not yet made public. | 
