What you need to know about mpox vaccines

The Democratic Republic of Congo, the epicenter of the current mpox outbreak, is finally receiving vaccines this week. The first batch of doses — a donation from the European Union — arrived on Thursday, and the country’s health ministry plans to start deploying the doses this weekend, according to the World Health Organization. Vaccines are long overdue in DRC, which has been battling a national outbreak of mpox since 2022. Mpox is endemic in DRC, which reported the first human case of mpox in 1970. Cases have grown over the years, and since 2005, the country has reported thousands of cases every year. But the emergence of a new strain of the virus, and its spread in other African countries where it has never been reported before, has caused great concern, leading the Africa Centres for Disease Control and Prevention and WHO to declare it a public health emergency on the continent and globally last month. Those declarations helped draw attention to the crisis, and prompted calls for vaccines to flow into the continent. The U.S., Japan and some European countries, as well as vaccine makers, have pledged to donate doses to DRC and other African countries. UNICEF has come out with an emergency tender to secure more doses, and WHO is currently reviewing three vaccines to help fast track their approvals so they can be used effectively to tackle the crisis. The first donations arrived in Nigeria last week. But DRC, which according to WHO is seeing a “rapid escalation” of mpox with more than 20,000 suspected cases, and outbreaks happening in different parts of the country, has not received a single dose of the vaccine — until today. The failure to get vaccines to DRC is part of a pattern of neglect often seen in diseases that mostly affect low-income countries, according to Rebecca Grais, executive director of the Pasteur Network and a member of SAGE, the group of experts which advises WHO on vaccines and immunizations. “There is significant underinvestment and lack of investment in diseases which affect the poorest of the world, the most underserved and the most vulnerable,” she told Devex. There is also no framework or mechanism in place to ensure equitable distribution of vaccines, she said. That’s part of the goals for the pandemic agreement, but countries have yet to agree on many of its details. They are set to resume discussions on the agreement next week. “Are these deliberations going to be successful by December or not? I don't know. But until we have something like that, this scenario will repeat over and over and over again,” Grais said. While not a silver bullet, vaccines are a critical part of the response to the outbreak. Here’s what we know so far about mpox vaccines. What vaccines are available for mpox? The vaccine donated to Nigeria by the U.S. government is called MVA-BN, which stands for modified vaccinia Ankara-Bavarian Nordic — the latter a reference to the Danish company that developed it. It uses a weakened strain of the vaccinia virus and is nonreplicating, preventing it from causing disease. The vaccine is called by different commercial names: Jynneos in the U.S., Imvanex in Europe, and Imvamune in Canada. It was widely used by different countries during the mpox global health emergency in 2022. But there are two other vaccines that can also be used against mpox — LC16 by Japanese company KM Biologics and ACAM2000 by U.S. company Emergent BioSolutions. Similar to MVA-BN, these vaccines were originally intended for smallpox, but received authorization in some countries to be used against mpox. There are candidate vaccines for mpox in pre-clinical and clinical stages of development. Moderna and BioNTech — one of the companies behind the COVID-19 vaccine known as Comirnaty — are each working on vaccines based on RNA. However, these are still in the early phase of clinical development. It’s important to note that vaccine supplies are currently limited, and WHO does not recommend mass vaccination. Where are these mpox vaccines approved for use? MVA-BN is approved for use against mpox in several countries. According to data presented by Marco Cavaleri, head of the public health threats department of the European Medicines Agency during the WHO co-hosted mpox research conference last month, the vaccine is currently authorized for use in the U.S., Canada, EU, U.K., Nigeria, Switzerland, DRC, and Singapore. Emergency use authorization of the vaccine in Nigeria and DRC is until July and June 2025, respectively. In the EU and in the UK, it has been given marketing authorization “under exceptional circumstances.” LC16 is currently authorized in Japan and DRC, the latter also under emergency use. ACAM2000 is approved for use in Singapore, Australia, and Canada. The U.S. Food and Drug Administration has recently expanded its use for mpox. WHO is currently reviewing the three mpox vaccines for emergency use listing, a move that can help expedite approval and usage of the vaccines in countries that do not have stringent regulatory bodies. WHO said on Wednesday that MVA-BN “fits the requirements” for prequalification and that it might be able to conclude its evaluation of the vaccine next week, depending on responses from the company. Critics have said WHO could have done this earlier. Bavarian Nordic, for example, said it has submitted data to WHO as far back as May 2023 on MVA-BN, according to a report by The New York Times. But the U.N. agency argued the process can only be made following the declaration of a public health emergency of international concern, and that it didn’t have all the data needed to make a prequalification. Who should receive what vaccine? SAGE has made recommendations on mpox vaccination. According to Grais, WHO recommends that nonreplicating vaccines such as MVA-BN, minimally replicating vaccines like LC16, replicating cell-culture-derived vaccinia-based vaccines like ACAM2000 or equivalent vaccines can be used for healthy individuals who are not pregnant but who are at high risk of getting mpox, such as health care workers and people who have been exposed to it. This includes those who’ve been in contact with someone with mpox and people living in an area where there’s a lot of case transmission. However, ACAM2000 has some concerns around its safety profile. It has shown cases of myopericarditis — inflammation of the heart muscle and outer lining — among those who received the vaccine in clinical trial and observational studies, according to a WHO position paper. Thus experts advise preference for the other two vaccines. MVA-BN or LC16 may be used for children or those under 18 years old. This is crucial, given that children bear the brunt of mpox cases in DRC. Studies have shown that both vaccines have good safety profiles when given to children, although MVA-BN is currently not licensed for those under 18 years of age. LC16 is approved for use in children under 18 only in Japan, while MVA-BN was only approved for emergency use for those under the age of 18 during outbreaks in the U.S in 2022. However SAGE said MVA-BN may be used in infants, children, and adolescents when the benefits of vaccination outweigh potential risks in an outbreak setting. The same goes for pregnant women. But several trials are underway to further test vaccines’ efficacy and safety in different populations, and generate the evidence needed to increase children’s and pregnant women’s access to mpox vaccines. Bavarian Nordic has submitted data on a clinical study conducted in the U.S. and Puerto Rico on the use of the vaccines in adolescents aged 12-17 years old, which the European Medicines Agency is currently assessing. The Coalition for Epidemic Preparedness Innovations, or CEPI, is also supporting a trial of the vaccine in children aged 2 to 12 years old. The CEPI-supported trial is due to start in the next two months, pending regulatory and ethical approvals, according to Kristine Rose, mpox disease program lead at CEPI. They plan to do the trial in DRC and Uganda, but said the locations will be confirmed once they receive regulatory approval to proceed. CEPI is also anticipating later this month — again subject to regulatory and ethical approvals — the start of the SMART trial, which will assess whether vaccinating high-risk individuals, such as those who came into contact with someone with mpox, with the MVA-BN vaccine reduces their risk of illness and death from mpox. The trial will be conducted in Bukavu in DRC, and Kampala in Uganda, but “may also be extended to Nigeria,” Rose wrote. CEPI is also “looking to fund a study evaluating an mpox vaccine in pregnant women and infants,” she added, details of which are being still being finalized.