Based on the data - if you have 50-60% vaccination then I would think that that plus immunity would put you close to 70%, assuming some of those vaccinated have also had covid.
As the average continues to tick toward 1 million vaccinations per day, the 100 million in 100 days should be easily attainable, but then again that is less than 20% of the population.
Now 100 million fully vaccinated in 100 days would be THE goal.