  Twitter is one of the most popular social media platforms in the country, but
pre-pandemic vaccination debate has been shown to be polarized and siloed into
echo chambers. It is thus imperative to understand the nature of this
discourse, with a specific focus on the vaccination hesitant individuals, whose
healthcare decisions may affect their communities and the country at large. In
this study we ask, how has the Italian discussion around vaccination changed
during the COVID-19 pandemic, and have the unprecedented events of 2020-2021
been able to break the echo chamber around this topic? We use a Twitter dataset
spanning September 2019 - November 2021 to examine the state of polarization
around vaccination. We propose a hierarchical clustering approach to find the
largest communities in the endorsement networks of different time periods, and
manually illustrate that it produces communities of users sharing a stance.
Examining the structure of these networks, as well as textual content of their
interactions, we find the stark division between supporters and hesitant
individuals to continue throughout the vaccination campaign. However, we find
an increasing commonality in the topical focus of the vaccine supporters and
vaccine hesitant, pointing to a possible common set of facts the two sides may
agree on. Still, we discover a series of concerns voiced by the hesitant
community, ranging from unfounded conspiracies (microchips in vaccines) to
public health policy discussion (vaccine passport limitations). We recommend an
ongoing surveillance of this debate, especially to uncover concerns around
vaccination before the public health decisions and official messaging are made
public.
