The first thing you mentioned (using public transit more) is not systemic racism. But maybe you just meant that as an effect leading to exposure, not as an example of racism.
The second thing you mentioned was discrimination in hiring. How is that systemic? I dare say that every company has anti-racism policies. Most have minority hiring programs. The fact that they do not hire more minorities is not due to anything systemic. Do you agree with that? Indeed, a racist HR person throwing away minority resumes would be in direct contravention of systemic policies which are in place to stop such activities, and so such acts would be individual racism in violation of systemic anti-racism.
It sounds like you are saying that blacks are statistically poor and urban, and the urban poor are exposed more. That is not systemic racism; it is an observation of statistics. I suppose you could argue that past systemic racism leaves blacks in a position of being more likely to be poor...So maybe early vaccines would be a reparation of sorts. But, in your second post, you said there is systemic racism now, which is why I was looking for an example.
If you said the urban poor regardless of race should get vaccines first, instead of African Americans, it might be more fair (and less racially divisive).