COVID Vaccination Strategies: When Is One Dose Better Than Two?

The number of people vaccinated once (yellow) and twice (green) under the prime first and prime boost scenarios. Prime first vaccinates double the number of people initially, while prime boost focuses on full vaccinations. Credit: Lucas Böttcher and Jan Nagler

Under certain conditions, vaccinating more people with a single dose slows virus spread.
In many parts of the world, the supply of COVID-19 vaccines continues to lag behind the demand. While most vaccines are designed as a two-dose regimen, some countries, like Canada, have prioritized vaccinating as many people as possible with a single dose before giving out an …