WASHINGTON (AP) - It sounded so ambitious at first blush: 100 million vaccination shots in 100 days.Now, one month into his presidency, Joe Biden is on a glide path to attain that goal and pitching well beyond it to the far more ambitious and daunting mission of vaccinating all eligible adults against the coronavirus by the end of the summer.Limited supply of the two approved COVID-19 vaccines has hampered the pace of vaccinations — and that was before extreme winter weather delayed the delivery of about 6 million doses this past week.
But the United States is on the verge of a supply breakthrough as manufacturing ramps up and with the expectation of a third vaccine becoming available in the coming weeks.RELATED: Biden says federal.