You're the one who brought up comparing it to Covid, not me. Percentages are more meaningful than raw numbers in most cases.
As for how many of these late term abortions are considered medically necessary, I haven't been able to find any hard statistics on that. Admittedly, I didn't spend a lot of time looking as I think it isn't worth looking into when it's such a small subset of the argument. Regardless "partial birth abortions" is a somewhat misleading term as they are not something occurring during labor at 40+ weeks, but occur around the 21st week in a vast majority of cases:
"The CDC does not elaborate on the breakdown by gestational age for abortions occurring past 21 weeks, but it is likely that the vast majority occur soon after 21 weeks rather than in the later in the pregnancy. While very limited data exists on this issue, a study
from 1992 estimated 0.02% of all abortions occurred after 26 weeks gestation (320 to 600 cases per year). This may overestimate current day numbers, given the abortion rate is currently at a historic low
, and restrictions on abortions later in pregnancy have increased. " (quote from the second article linked below)