Model studies of monkeypox vaccines provide a roadmap for vaccination

A modelling study exploring the optimal distribution of monkeypox virus vaccine (MPXV) provides a roadmap for public health to maximize the impact of
limited vaccine supply.
The article, published in CMAJ (Journal of the Canadian Medical Association) confirms that it is best
to prioritize vaccines to large networks with more initial infections and greater transmission potential.

"We hope that these insights can be applied by policymakers in the context of diverse and dynamic epidemics in Canada and elsewhere to maximize the avoidance of infection early in epidemics where vaccine supply is limited," said Dr Sharmistha Mishra, MAP Centre for Urban Health Solutions at Toronto's
Unified Health Centre.

As of November 4, 2022, there were 1,444 cases of MPXV in Canada, a disproportionately high
proportion of gay, bisexual, and other men who have sex with men (GBMSM).
The existing supply of smallpox vaccine is very limited and priority is being given to populations at disproportionate risk
.

The researchers modeled two hypothetical cities as interconnected networks with a total size of 100,000 people in GBMSM communities
.
The team then changed the characteristics of the two cities in a reasonable set of settings and simulated the rollout of 5,000 doses
shortly after the first MPXV case was detected.

They found that the most powerful factors in optimizing vaccine distribution between cities were the relative number of reproductions (epidemic potential), initial case share, and city (or network) size
in each city.
If a larger city has a greater epidemic potential and most initial cases, it is best to allocate most of the vaccine to that city
.
The team changed the number of reproductions with a single parameter, but they highlighted how many factors can influence local epidemiological potential, including the density and characteristics of sexual networks, access to prevention and care, and the underlying social and structural context
of formative networks and accessibility.

"Based on our modeling assumptions, we found that vaccines generally avert more infections when they are prioritized to larger networks, networks with more first-time infections, and networks with more pandemic potential," wrote
lead author and doctoral candidate Jesse Knight at the University of Toronto.
He is a PhD student
at the MAP Centre for Urban Health Solutions at the University of Toronto.
"Our findings further underscore the importance of
global vaccine equity in responding to outbreaks and preventing them in the first place," he said.

The study highlights the interlinkages between regions and highlights the need for
a population-level perspective.

"Strategic prioritization of limited vaccine supply based on network-level risk factors can minimize infection
in the context of emerging epidemics, such as the current global MPXV outbreak," the authors concluded.