Despite the availability of vaccines, influenza remains a
major public health challenge
. A key
reason is the virus capacity for immune escape: ongoing evolution
allows the continual
circulation of seasonal influenza, while novel influenza viruses invade
the human population to
cause a pandemic every few decades. Current vaccines have to be
updated continually to keep
up to
date with this antigenic change, but
emerging
‘universal’
vaccines
–
targeting more
conserved components of the influenza virus
–
offe
r the potential to act across all influenza A
strains
and
subtypes.
Influenza vaccination programmes around the world are
steadily increasing in their population
coverage
. In future, how
might
intensive, routine immunization with
novel
vaccines
compare
a
gainst
similar
mass
programmes utilizing
conventional vaccines?
Specifically, how might
novel
and conventional
vaccines compare
,
in terms of cumulative incidence and
rates of antigenic
evolution of seasonal influenza?
W
hat are the
ir
potential implications for the impact of pandemic
emergence?
Here we
present a new
mathematical model, capturing both transmission
dynamics and
antigenic
evolution of influenza
in a simple framework
, to explore these
questions.
We find that
, even when m
atched by per
-
dose efficacy,
universal vaccines
c
ould dampen
population
-
level
transmission
over several seasons
to a greater extent
than conventional
vaccines
.
Moreover,
by lowering opportunities for
cross
-
protective immunity
in the population
,
conventional vaccines
could allow the
increase
d
spread of a novel pandemic strain.
Conversely,
u
niversal vaccines could
mitigate both seasonal and pandemic spread. However, where
it is not
possible to
maintain annual, intensive
vaccination
coverage,
the duration
and breadth
of
immunity raised by universal vaccines
are
critical
determinants of their performance relative to
conventional vaccines.
In future,
conventional
and novel
vaccines are likely to play
complementary roles in vaccination strategies
against influenza:
in this context,
our results
suggest important characteristics to monitor during the clinical development of emerging
vaccine technologies.