Because some covid vaccines will be available by the first quarter of this coming year.
And more than likely, they will prioritize the athletes to get inoculated.
But for the audience, I don't know how they can contain the possible infection.
Maybe lessen the audience and require some sort of certificate stating they got vaccine shot.
Things will get more complicated. There are multiple vaccines available in the market, with varying efficiency. The vaccines from Moderna and Pfizer claim up to 95% efficiency, while the one being developed by AstraZeneca/Oxford is less than 70% efficient. The question is whether the host nation would accept athletes who are inoculated with these less-efficient vaccines or not. And also, what will happen, in case these athletes are allowed to come to Japan and they later test positive for COVID 19?