When Biden took office there were more than 10 million Americans sick with covid, and more than 100,000 getting sick every single day.
Trump placed the initial orders of vaccines with the "Warp Speed" programs, but once the drugs were ready for distribution, he didn't place any more vaccine orders with the drug companies after he lost the election. Instead, Trump issued an Executive Order which said that American drug manufacturers couldn't export any covid drugs or vaccines until, all Americans had been vaccinated.
trumpwhitehouse.archives.gov
1.3 million people were getting sick every week, and 21,000 people were dying every week. Nearly 200,000 people per week getting sick. More than 3,000 people a day were dying.
None of that magically ended the day Biden took office. Instead, Republicans started actively campaigning against mask mandates, and vaccines, and telliing their voters Democrats were simply trying to "control" them.