Public health officials evaluating vaccination campaigns have traditionally used uptake rate, the proportion of the eligible population that receives a vaccine, as the primary metric of a campaign's success, on the reasoning that higher uptake more closely approaches the threshold needed for herd immunity and that campaigns should therefore be judged chiefly by how many additional people they persuade to be vaccinated. Some epidemiologists have challenged the sufficiency of this metric, arguing that uptake rate alone conceals which populations are reached. A campaign that raises overall uptake from 60 percent to 75 percent by heavily vaccinating a population already close to full coverage, while leaving a hard-to-reach subpopulation at its original low rate, produces the same aggregate uptake gain as a campaign that instead closes most of the gap in the hard-to-reach subpopulation; yet the two campaigns leave the community with very different residual outbreak risks, since disease transmission concentrates disproportionately within under-vaccinated pockets even when the community-wide average looks similar. On this view, evaluators should track uptake separately by subpopulation rather than rely on a single aggregate figure. Others grant the force of this point but caution against overcorrecting: disaggregated tracking requires identifying and monitoring subpopulations, which itself demands resources and, if done crudely, risks the appearance of singling out particular communities for scrutiny in ways that could undermine the very trust a vaccination campaign depends on. They propose instead a narrower fix, tracking uptake within the specific highest-risk pockets identified by prior outbreak data, rather than disaggregating the entire population into many subgroups.