Currently, what is the most reasonable scientific thinking regarding how long a potential COVID-19 vaccine will give immunity for? Is the idea that a vaccine would only have to be administered once and provide immunity for life, or is it expected to wear off after some time period and need to be re-administered? If so, what is that time period? If it doesn’t last very long, then I would be very concerned that even with a vaccine we would still have massive problems dealing with this.