In May 2022, the UK experienced a national outbreak of mpox disease, with case numbers rising rapidly particularly amongst gay, bisexual, and other men who have sex with men (GBMSM). This research linked laboratory data with survey responses to assess the effectiveness of a vaccine to those at risk.

Why did this work happen?

Mpox, formerly known as monkeypox, is an infectious disease which causes symptoms including a painful rash, enlarged lymph nodes and fever. Anyone can get mpox as it spreads through physical contact, as well as through contact with contaminated animals or materials.

In 2022, mpox started to spread amongst the GBMBM communities, with approximately 3500 cases in the UK, and more across Europe and the wider world. The UK Health Security Agency (UKHSA) quickly implemented public health measures to control the outbreak such as isolation and surveillance of cases and contacts, as well as recommendations of a vaccine for those most at risk.

The MVA-BN vaccine was developed for smallpox, but had shown to offer protection against mpox also in some studies in Africa. However, there was no real-world data on the effectiveness of the vaccine against mpox disease in humans before the 2022 outbreak. This piece of research aimed to rectify this.

How was data used?

UKHSA distributed questionnaires to individuals in England who had confirmed or highly probable cases of mpox. Questionnaires were sent via email or text, and asked questions about demographics, vaccination history, symptoms, and sexual orientation. Completion of the questionnaire was voluntary, with data held securely in accordance with the Data Protection Act 2018 and Caldicott Principles.

Personal identifiers in the returned questionnaires, such as name and date of birth, were then used to link the questionnaires to laboratory data and a public health case management system (HP Zone) to obtain additional information. The UKHSA has statutory approval to collect data for infectious disease surveillance and control without individual patient consent. By linking this data together, the researchers were able to better estimate the effectiveness of the vaccine.

What were the benefits?

Researchers were able to determine that the MVA-BN vaccine was 78% effective against symptomatic mpox at least 14 days after a single dose. This means there is no evidence of effectiveness in the first 13 days after vaccination. These findings supported those of similar studies. This suggests a relatively high level of protection, making it a useful tool for mpox outbreak control, but that there may be benefit in prioritizing delivery of the first dose. It also allows for patients who receive the vaccine to follow recommendations that they continue to follow isolation guidelines for a fortnight after vaccination to allow time for the effectiveness to kick in.

Who funded and collaborated on this work?

The research was funded and conducted by UKHSA.

Where can I go for more information?

Effectiveness of one dose of MVA–BN smallpox vaccine against mpox in England using the case-coverage method: an observational study

A news story which gives a digestible version of the academic article