Far from being brought under control, the monkeypox outbreak is growing rapidly, with the number of confirmed cases doubling to in the past week. The World Health Organization (WHO)’s emergency committee may declare it a public health emergency of international concern – its highest alert level – in the coming days. But how can it be controlled?
The UK is offering vaccination to those most at risk amid this particular outbreak, such as some men who have sex with men. Despite monkeypox not being a sexually transmitted infection, it can spread via skin-to-skin contact, inhaling infected droplets or sharing contaminated objects, like bedding.
This vaccination approach should halt the outbreak if enough people are immunised, assuming other countries follow suit.
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“This is a disease where herd immunity can be achieved, unlike covid,” says at the University of East Anglia in the UK. “Given that monkeypox is not that infectious and vaccination tends to give long-lasting immunity, then immunising a proportion of the current or potential future risk groups will go a long way to bringing the current epidemic to an end.”
The bad news is that vaccine supplies are limited.
When the outbreak began in early May, the expectation was that it wouldn’t last long. In West and Central Africa, where monkeypox is endemic and circulates in some animals, the virus often jumps to people, but doesn’t usually spread widely.
And when monkeypox has previously spread beyond non-endemic regions of Africa, there were only a handful of cases, typically from the same household. The current outbreak is by far the biggest the world has even seen and looks poised to get bigger.
Most cases have been mild, with no deaths reported so far. This may seem surprising given that this type of monkeypox has a reported death rate of around 3 in 100. Deaths in previous outbreaks, however, were , and in countries with less healthcare access.
The big question is why the outbreak is so much bigger than previous ones. Genomic studies suggest the circulating virus is closely related to those that caused a handful of monkeypox cases in 2017 and 2018, both within endemic regions of Africa and outside these areas. The circulating virus doesn’t appear to have any major changes that make it more transmissible among people.
Although anyone can contract monkeypox, there are currently higher levels of transmission among men who have sex with men. According to a modelling study by at the London School of Hygiene & Tropical Medicine and his colleagues, the size of the outbreak in the UK to start spreading within this population.
Based on surveys, the model suggests a small proportion of men who have sex with men have a larger number of partners and change partners more frequently than other groups. This means the odds of the virus spreading via sex are high among men who have sex with men, but sex may not be key to the transmission of the virus in other people.
Countries like the UK have been tracking and tracing cases’ contacts, asking people to isolate and offering them the smallpox vaccine Imvanex.
But track and trace alone is insufficient. On 21 June, the UK Health Security Agency announced it would extend , offering immunisation to men who have sex with men and have multiple partners, participate in group sex or attend “sex on premises” venues.
Whether there are enough vaccine doses is less clear. The US had nearly 30 million doses of Imvanex (known there as Jynneos), but most have expired, , enough for 700,000 people to get the required two doses. Its manufacturer, Bavarian Nordic, has enough bulk vaccine to fill another 1.4 million doses and has begun that process, a spokesperson told żěè¶ĚĘÓƵ.
However, its production facility is closed for expansion, so further doses are unlikely until 2023, says the spokesperson.
How many doses will be needed is unclear, says Hunter. If you assume the number of men at high risk is similar to the number seeking HIV tests, he says, that would be around 150,000 in the UK alone.
North America and Europe might have enough to meet the initial vaccine demand, but that would leave none for the rest of the world. And if monkeypox starts spreading more widely, North America and Europe won’t have enough, says Hunter.
Some countries have older smallpox vaccines but the WHO as they don’t meet modern safety standards.
