One 20 is not unusual. That said, that does not mean that the vaccine is not effective at being a vaccine. A vaccine isnt just about your immunity, but about he

One 20 is not unusual. That said, that does not mean that the vaccine is not effective at being a vaccine. A vaccine isnt just about your immunity, but about herd immunity. When you create an inability for a virus to spread among the herd, you protect those who are unable to acquire immunity by inhibiting the viruses ability to move between hosts and persist in a population. Vaccines are not 100% effective for each individual.