The way vaccine doses are delivered in different sections of a country during the early stages of a viral outbreak could play a significant influence in controlling the infection and the rate at which it spreads. For example, providing more COVID vaccines in a place with a large population and a high COVID infection rate may result in faster herd immunity than doing the same in a small population & low infection rate.
According to a press release, a team of researchers at Unity Health Toronto in Canada has presented a monkeypox vaccine allocation strategy that attempts to offer the greatest results with a limited vaccination supply. The researchers state in their study that there are 1,444 patients with monkeypox, with a disproportionate number of those belonging to the GBMSM community (men having sexual relationships with other men, gay, and bisexual population).
They also show that there are very few vaccines available for the GBMSM community, which is at disproportionate risk for the monkeypox virus (MPXV) is very limited. They have therefore created a successful vaccine distribution approach that could stop the infection in such a situation.
Ensure appropriate vaccination allocation for monkeypox
The researchers built two hypothetical cities as partially connected networks with a total GBMSM population of 100,000 people. The first city, known to as city A, was a model of a big city such as Toronto, with a GBMSM population of 80,000. City B, which represented medium & small cities, had only 20,000 members of the GBMSM.
First, MPXV is introduced into the model, and after 45 days, 5,000 vaccination doses are administered over the course of 30 days. The vaccines are distributed through networks based on city size, initial case percentage, and epidemic potential.
“This potential is often quantified by the baseline reproductive number R0, which reflects the expected number of secondary infections generated by an infected individual in a fully susceptible population,” the authors note to his study. They further state that an optimal vaccine allocation approach for both cities would be the one that results in the lowest monkeypox infection rate by Day 90.
Throughout the experiment, the total quantity of vaccine doses for both locations was kept to 5,000. The researchers used various vaccine allocation algorithms that included both equal & unequal vaccine distribution scenarios.
Based on the infection rates seen in these various situations, they determined that the ideal way is to provide maximal vaccine doses to an area with the greatest epidemic potential and the greatest number of early cases.
“Because of the bigger population size, stronger epidemic potential (R0), and having all imported or seed cases in city A in this scenario, allocating all 5000 vaccine doses to city A yielded the fewest infections (550) by day 90 (optimal strategy),” the authors wrote in their article. Vaccines allocated proportionally to city size resulted in 615 infections (broken line), whereas no vaccination yielded in 1020 infections.”
They further explain that administering the maximum number of doses to one city based on R0 and initial cases could also lead to high rates of monkeypox infections in another city. However, since most of the infection is already prevented in a short time (90 days), it would be easy to control the remaining cases in the city with a low R0 once the vaccine supply increases.
More than 29,000 cases of monkeypox (and 14 fatalities) have been documented in the US alone as of November 25. The researchers hope their findings will help policymakers in Canada and other countries develop an optimal vaccine allocation strategy to control the current monkeypox outbreak.
The study was published in the Canadian Medical Association Journal.