Side Effects Of Covid Booster How Long Does It Last. If you're weighing the side effects of the vaccine versus the effects. In trials of both the moderna and pfizer vaccines, more people experienced side effects after the second dose.
Other less common side effects include: You may experience some side effects, similar to those you might’ve had after the first or second dose, such as muscle aches, pain at the injection site or headaches. On average, these side effects lasted between two and three days.