Ontario’s top doctor announced today that they will expand eligibility for a fourth COVID-19 booster vaccine shot as other provinces do the same. “Stay up to date with your COVID vaccinations,” Dr. Kieran Moore said, adding that the expanded eligibility is a “real call to arms” to those who have an underlying illness or are more at risk. Jamie Mauracher looks at whether or not the timing of the booster shot matters, and when exactly people should be looking at getting the booster dose for maximum efficacy.