You consider yourself to be in a higher-than-average risk cohort due to age and/or a couple of potential underlying conditions, neither of which really cause you problems on a day-to-day basis (ie. they are controlled by medication).
For a transcontinental non-stop flight, would you rather:
Fly now in a first class section where there are ten seats available but you know only two will be booked, only 50 of 138 seats will be booked in the main cabin, and masks are required. You have an N95 mask.
A 50% effective (whatever that means) vaccine is available. You are eligible to be vaccinated soon after one is available, and get it. But the plane will be full and masks will not be required. You would be flying in the early timeframe of overall vaccine distribution (ie. your cohort is eligible but it has not been distributed outside that cohort). You will be in first class where there is more separation (but not nearly as much as in scenario 1). You have an N95 mask.
Waiting until everybody who wants a vaccine has gotten it is not an option.