Outcome measures
blisters, rash
EMERGENCY, SMALLPOX
Self-isolation intention was measured using two items, asking participants to imagine that they were contacted by public health officials and told that they needed to self-isolate for 21 days because they had mpox, and because they had come into high-risk contact with a case. Responses were given on a five-point scale from ‘definitely would not’ to ‘definitely would’. The order of items was randomised between participants to mitigate potential order effects. As answers on both items were highly correlated across all respondents (r=0.77, p=0.001), we combined responses to give a 9-point scale (2–10; summing responses ‘definitely would not’=1 to ‘definitely would’=5; higher number indicates greater intention).To measure help-seeking intention, participants were asked to imagine that they developed an unexplained rash with blisters and learnt that they had come into contact with a mpox case. They were then asked what they would do, from a list of 10 behaviours including waiting to see if they got better, contacting healthcare services, letting people you had been in recent close contact know and searching for information. Responses for each item were given on the same 5-point ‘definitely would not’ to ‘definitely would’ scale. We created a binary variable, coding participants as intending to seek help immediately if they answered ‘probably’ or ‘definitely would’ to any help seeking where they would encounter a health professional (trying to book an appointment with a general practitioner, visiting a pharmacist/chemist, going to Accident & Emergency or another National Health Service (NHS) service, calling NHS111 or 999, visiting a walk-in sexual health clinic, or calling a sexual health clinic), and did not select ‘wait a day or two to see if they get better or clear up on their own’ versus did not select any help-seeking behaviour where they would encounter a health professional, or selected a help-seeking behaviour but also stated that they would ‘wait a day or two to see…’.Participants were then asked about their intended contact behaviour in the same scenario, being asked ‘in the following 21 days, realistically how much’ they would come into skin-to skin contact with others, have sexual contact, have sex without using a condom, go to a crowded place, help or provide care for a vulnerable person, and go to a public place where they may come into physical contact with someone else. For each item, participants responded ‘I would completely stop doing this’, ‘less than normal’, ‘same as normal’, ‘more than normal’, ‘not applicable, I wouldn’t do this anyway’, ‘don’t know’ or ‘prefer not to say’. We focused our analyses on the item asking about sexual contact (from kissing to intercourse) with other people, recoding it into a binary item (‘I would completely stop doing this’ vs would do this less than, same as, or more than usual). Answers of ‘not applicable, I wouldn’t do this anyway’, ‘don’t know’ and ‘prefer not to say’ were coded as missing.We measured intention to share details of close contacts by asking participants to indicate how likely they were, if asked by public health officials, to share contact details of every person who had been in their home, they had had sexual contact with, they had skin-to-skin contact with, and that they had shared bedding, towels or clothes with in the last 7 days, and every place they had had sexual contact with someone. Responses were given on a 5-point ‘definitely would not’ (1) to ‘definitely would’ (5) scale. We used the most recent official guidance on contact tracing available at the start of data analysis to select the item most relevant to contact tracing efforts (identifying every person you had sexual contact with in the last 7 days).Participants were asked if they had received a smallpox vaccine in 2022. Those who indicated they had not had a vaccine were asked about their vaccination intention. We asked participants how likely they would be to have a smallpox vaccine if they were offered one. Responses were given on a 5-point ‘definitely would not’ (1) to ‘definitely would’ (5) scale.