  This work consists of an epidemic model with vaccination coupled with an
opinion dynamics. Our objective was to study how disease risk perception can
influence opinions about vaccination and therefore the spreading of the
disease. Differently from previous works we have considered continuous
opinions. The epidemic spreading is governed by a SIS-like model with an extra
vaccinated state. In our model individuals vaccinate with a probability
proportional to their opinions. The opinions change due to peer influence in
pairwise interactions. The epidemic feedback to the opinion dynamics acts as an
external field increasing the vaccination probability. We performed Monte Carlo
simulations in fully-connected populations. Interestingly we observed the
emergence of a first-order phase transition, besides the usual active-absorbing
phase transition presented in the SIS model. Our simulations also show that
with a certain combination of parameters, an increment in the initial fraction
of the population that is pro-vaccine has a twofold effect: it can lead to
smaller epidemic outbreaks in the short term, but it also contributes to the
survival of the chain of infections in the long term. Our results also suggest
that it is possible that more effective vaccines can decrease the long-term
vaccine coverage. This is a counterintuitive outcome, but it is in line with
empirical observations that vaccines can become a victim of their own success.
