By TOM MURPHY
AP Health Writer
Pfizer is seeking U.S. approval of a booster dose of its two-shot COVID-19 vaccine. The drugmaker announced Wednesday that it has started the approval process for a third dose of its vaccine for all Americans ages 16 and older. The company said it expects to complete its application with the Food and Drug Administration by the end of this week. U.S. health officials last week announced plans to dispense COVID-19 booster shots to all Americans to shore up their protection amid the surging delta variant of the virus. Pfizer’s vaccine received full regulatory approval this week.