Mpox is on the rise again as outbreak gathers pace

The original mpox outbreak began in 2022, but case numbers have rumbled on, despite countermeasures. Ben Hargreaves finds that a new variant of the virus is spreading more rapidly, and the response is scaling up in turn.

The world is facing another public health emergency, after the WHO determined that a surge in cases of mpox, formerly known as monkeypox, constitutes a serious concern to global health. COVID-19 underlined how vulnerable the global community is to virulent infectious diseases, and also highlighted how important taking immediate action is in preventing pandemics. WHO director-general Dr Tedros Adhanom Ghebreyesus’ decision to declare mpox a serious threat and to call on coordinated international action to suppress its spread marks an escalation in the international approach to the virus.

Unlike the COVID-19 pandemic, there already exist vaccines that are effective against mpox and the viral illness has also been known about for decades. These two factors mean that countermeasures can be taken swiftly against the spread, but only if the international community acts quickly to counter the threat. Already, cases have been confirmed outside of Africa and the necessity to tackle the spread is growing more urgent.

A deadly threat

The mpox virus was first detected in Denmark in 1958, when it was discovered in monkeys kept for research. The first reported case of human infection occurred in 1970, when a nine-month-old boy in the Democratic Republic of the Congo (DRC) was found to be carrying the virus. However, the virus has gained notoriety since 2022, when a major outbreak occurred in some African countries, before going global, and the virus has persisted in the Central African region.

The latest outbreak has emerged in the Democratic Republic of Congo, where the number of cases has been increasing steadily over the past decade. The recent rise of infections coincides with a new virus strain, clade Ib, which appears to be spreading rapidly. In 2023, reported cases increased significantly and that trend has continued into 2024, with 15,600 cases already reported and 537 deaths from the virus. Neighbouring countries to the DRC have reported cases, while the virus has also made the jump to countries such as Liberia, the Ivory Coast, and South Africa, despite not sharing borders with countries reporting infections. In a sign of the spread of the virus, Sweden and Thailand have also confirmed cases of mpox, whilst there are also potential cases in Pakistan.

In terms of the dangers of the virus itself, the common symptoms are rash, fever, sore throat, and muscle aches. The rash often begins on the face and spreads over the body, extending to the palms of the hands and soles of the feet. Children, pregnant women, and people with weak immune systems are at a higher risk of serious illness and death. Due to the rashes that appear, individuals can also suffer from infection with bacteria, leading to serious health complications.

The efforts to prevent the spread of the virus are complicated by the signs and symptoms of infection potentially occurring between one and 21 days after exposure. Mpox can also pass to other people until all sores have completely healed, and some people can be infected without developing any symptoms.

A measured response plan

Following its declaration of a public health emergency, the WHO continued its action by launching a global ‘Strategic Preparedness and Response Plan’. Within the document are three primary objectives as part of the organisation’s response strategy: rapidly detect and control outbreaks; advance research and ensure equitable access to medical countermeasures; and minimise transmission between humans and animals.

The first objective is centred on implementing effective surveillance, response, and community engagement strategies, with the overall aim to detect, contain, and manage mpox outbreaks. The second is focused on promoting research and development to address knowledge gaps, whilst also ensuring equitable, risk-based access to and timely delivery of diagnostics, vaccines, therapeutics, and other essential health products. The final aim is to strengthen collaboration across human health, animal health, and environmental sectors to understand and reduce the risk of mpox transmission between animals and humans.

Within the organisation’s overall strategy, there is a central role for vaccines to be used to interrupt transmission of the virus. This is able to help by allowing enhanced control strategies by implementing targeted vaccination by focusing on those at the highest risk of infection, thereby reducing overall transmission. The WHO has called on countries with vaccine stockpiles to make doses available to affected regions, as well as requesting that manufacturers review access and pricing policies to ensure vaccines are affordable and accessible in low- and middle-income countries.

Vaccine production ramps up

As mentioned, there are vaccines already developed that are able to protect against mpox, with three options on the market. One manufacturer is Bavarian Nordic, which created Jynneos (MVA-BN), a vaccine that protects against both smallpox and mpox. A spokesperson for the company told pharmaphorum that the vaccine works by stimulating an immune response against vaccinia, an orthopoxvirus, which is closely related to mpox, smallpox, and other poxviruses.

According to the spokesperson, the 2022 outbreak provided a large amount of data that helped to show that the vaccine provided strong protection against mpox, with vaccine effectiveness shown to be up to 90% after two doses. One of the challenges for manufacturers is to be able to produce at sufficient scale to deliver doses to the regions impacted by the virus. The spokesperson noted that Bavarian Nordic is now manufacturing at a large scale due to the higher base demand since the 2022 outbreak.

In August, Bavarian Nordic announced that it had received a 440,000- dose contract to supply the vaccine to an undisclosed European country. The vaccines will be delivered in 2024, as part of a wider capacity to supply up to 10 million doses by the end of 2025.

The spokesperson explained the thinking behind ordering such stocks of vaccines, and how the company had reacted: “When we saw the previous outbreak in 2022, which affected more than 100 countries worldwide, very few countries had stocks of mpox vaccines readily available. Since MVA-BN is made to order, it took us a while to ramp up production and meet the demand. However, we have since supplied our vaccine to a large number of countries, to meet both the initial demand, but also for stockpiling should the need arise to vaccinate more people over time.”

Such stockpiling by European nations would have seemed overly cautious only a few years ago, as there are very few confirmed cases of mpox within the region. However, the lessons learnt from COVID-19 mean that adopting a safety-first approach has become a higher priority. However, this action will need to be taken alongside supporting the impacted regions that are bearing the brunt of mpox infections and deaths.