"Vaccines became available shortly before the President came into office."

TRANSLATION:
Vaccines became available when President Trump was in office.

OR, AT LEAST

Vaccines became available shortly before President Biden came into office. [Biden is no more or less "the President" than Trump was "the President." Biden is simply "the current President."]

Is President Biden "responsible for fully vaccinating over 200 million people"? No. Hell no!

Presidents like to take credit for everything accomplished in the U.S. while they are in the White House. And they avoid, if at all possible, accepting blame for any domestic or foreign policy failures while they are in the White House. If a president seeks to claim credit or responsibility for everything good that occurs during his term of office, whether he had a personal hand in it or not, then we ought to insist that he accepts blame or responsibility for everything bad that occurs while he is in office as well. For Biden, that would mean his taking responsibility for the botched withdrawal from Afghanistan, for the current high rate of inflation (rather than calling it "Putin's price hike"), for the flood of illegal/unauthorized immigrants streaming across our southern border, and for all the people who have died from covid since his presidential inauguration.

The truth, as I see it, is that a president is not automatically responsible for everything good or bad that happens during his or her term of office. For example, tens of millions, and probably hundreds of millions, of Americans would have been vaccinated against covid by now no matter who occupied the White House.

American presidents are not known for their modesty. We should neither encourage nor applaud they're claiming as personal accomplishments all of America's successes during their term of office, nor should we allow them to blame others for their administration's shortcomings.