But with the focus on the first round, Pfizer CEO Albert Bourlasays says people may need to start thinking already about yearly shots. “A likely scenario is we will not have a third dose vaccine. How can Americans start thinking about annual shots starting next year? Dr. Pedro Piedra, a professor pediatric infectious disease specialist at Baylor College of Medicine, say it’s just too soon to know if annual shots for COVID-19 will be necessary. Doctors say 75% to 80% of the population vaccinated to achieve herd immunity.