This suggests that the data might be showing a lower than expected mortality rate post-vaccine, which could imply either a protective effect or possibly underreporting. But it's critical to consider how "background rates" are defined — if they're based on pre-pandemic data, they might not account for the increased risk factors in the vaccinated population. Also, the observed-to-expected ratio being below one doesn't automatically mean the vaccine is safe; it could just mean the population being studied was healthier to begin with. The real question is whether the study controlled for those variables properly.