  Vaccine adverse events have been presumed to be a relatively objective
measure that is immune to political polarization. The real-world data, however,
shows the correlation between presidential disapproval ratings and the
subjective severity of adverse events. This paper investigates the partisan
bias in COVID vaccine adverse events coverage with language models that can
classify the topic of vaccine-related articles and the political disposition of
news comments. Based on 90K news articles from 52 major newspaper companies, we
found that conservative media are inclined to report adverse events more
frequently than their liberal counterparts, while the coverage itself was
statistically uncorrelated with the severity of real-world adverse events. The
users who support the conservative opposing party were more likely to write the
popular comments from 2.3K random sampled articles on news platforms. This
research implies that bipartisanship can still play a significant role in
forming public opinion on the COVID vaccine even after the majority of the
population's vaccination
