Mpox knowledge, vaccination and intention to reduce sexual risk practices among men who have sex with men and transgender people in response to the 2022 mpox outbreak: a cross-sectional study in Victoria, Australia

Introduction

Mpox (also previously known as monkeypox or MPX) is a zoonotic orthopoxvirus, previously endemic in central or western Africa.^1–3 Mpox is endemic countries is primarily spread through animal-to-human contact or human-to-human via close skin-to-skin or household contacts, and it is not a typical sexually transmitted infection (STI).^4,5 However, outbreaks of human-to-human mpox cases were reported in several non-endemic European countries from May 2022 with a rapid increase in the number of these cases, that occurred predominantly among gay, bisexual, and other men who have sex with men (MSM).⁶ Given the multi-country outbreak of mpox,⁷ the World Health Organization (WHO) declared ongoing mpox outbreaks in multiple countries a Public Health Emergency on 23 July 2022.⁸ As of 23 November 2022, there were 80 850 confirmed cases and 55 deaths among 110 countries.⁹

The first mpox case in Australia was reported in May 2022. On 28 July 2022, Australia declared the mpox outbreak as a Communicable Disease Incident of National Significance in Australia. As of 10 November 2022, there were 141 notified mpox cases in Australia, almost half (n = 69) were reported in Victoria;¹⁰ and most cases had been diagnosed among MSM.

Data have shown that the first-generation smallpox vaccines are effective (~85%) at cross-protecting against mpox;¹¹ several countries (including Australia) have used the third-generation smallpox vaccine (modified vaccinia Ankara – Bavarian Nordic, MVA-BN) in their mpox vaccination programs in response to this mpox outbreak; however, the effectiveness of the third-generation vaccine against mpox in human is still not completely clear. Although some studies have demonstrated a relatively low level of virus-neutralising antibodies after MVA-BN vaccination,¹² it is anticipated that these vaccination programs would be effective without having the definite evidence.

In Victoria, free mpox vaccines (JYNNEOS vaccine) have been available to eligible individuals since 12 August 2022. The primary aim of the mpox vaccines was used for pre-exposure prophylaxis in this campaign; however, vaccines can also be given as post-exposure prophylaxis if individuals have close contacts of mpox cases within 4 days.¹³ Because the initial stocks of the vaccine were limited, the first phase of the Victorian mpox vaccination program targeted higher risk sexually active MSM and transgender people who had had at least one STI in the past 12 months, or attending sex-on-premises venues (SOPV) or who were intending to travel to Europe or North America before 31 October 2022.¹⁴ This first phase of vaccination was only able to provide the first dose to 3500 MSM.^15,16 The second phase of vaccination commenced in November 2022 targeting a wider population who were at-risk of mpox. Furthermore, several Australian community-based organisations in collaborations with the Department of Health have also launched public health education messaging on mpox via social media to increase the awareness of mpox and uptake of mpox vaccination.

At the beginning of this mpox outbreak, the primary mode of transmission was unclear although there has been cumulative evidence suggesting that mpox is primarily spread through sexual contact in this mpox outbreak.^5,17–20 Furthermore, people who are diagnosed with mpox in this outbreak usually present with genital or anal lesions,^19,20 which is not usually seen in previous mpox outbreaks in central or western Africa. It is also estimated about 14% of the severe mpox cases in this outbreak have required hospitalisation globally.²¹ With the new natural history and clinical presentation of mpox in this outbreak, it is reasonably hypothesised that people may change their sexual practices in order to reduce their risk of contracting mpox as a prevention strategy in the absence of widely available vaccines, and this approach was also seen in other pandemics such as HIV and coronavirus disease 2019 (COVID-19).^22,23 Most international studies on mpox vaccination examining the willingness and determinants of receiving mpox vaccination but there have been very limited studies examining the changes in sexual practices during the mpox outbreak.^24–29 A better understanding of the sexual practices of at-risk population may help to adjust prevention policies or strategies. This study aimed to examine community understanding of mpox, attitudes towards vaccination, and potential changes in sexual practices due to the mpox outbreak among MSM and transgender people in Victoria, Australia.

Materials and methods

Results

A total of 563 eligible participants consented to participate in the study and 537 (95.4%) completed the questions to key variables for analyses and were included in the final analysis; of these, 531 (98.9%) had complete data. Table 1 shows the median age of the participants was 33 years (IQR 28–42) and almost all were cisgender men (99.1%, 532/537). Most were highly educated with 69.8% (375/537) completed a university degree. Two-thirds of the participants (68.9%, 370/537) were recruited from a sexual health clinic, and one-third (31.1%, 167/537) were recruited from the community. The median number of male sexual partners in the past 12 months was 10 (IQR 4–20), and 42.1% (226/537) reported having an STI diagnosis other than HIV in the past 12 months.

Most participants (97.8%, 525/537) had heard about mpox, 10.5% (55/525) knew someone who had had mpox, and a small proportion (1.3%, 7/525) had had close contact with someone who was diagnosed with mpox. Of the 12 mpox knowledge questions, the median score of correct answers was 10 (IQR 8–11). Table 2 shows that more than one-third of the participants (38.3%, 201/525) stated mpox was a newly discovered virus. Most participants correctly identified mpox could be transmitted through sexual contact with an infected person (94.7%, 497/525), and infected individuals would have flu-like symptoms (88.1%, 461/523) and ulcers, blisters or sores (97.3%, 509/523). More than two-thirds of participants (68.7%, 360/524) correctly identified the smallpox vaccine was thought to be effective against mpox. However, 29.8% (156/524) participants reported there was no effective vaccine, nor did they not know any vaccine that was effective against mpox. Only 5.0% (26/525) of participants did not know how mpox could be transmitted. The median score in relation to the concern about catching mpox was 6 (IQR 4–8), with 17.7% (91/515) scoring 10 (very concerned). The median score of the perceived severity of sickness when the individuals had mpox was 7 (IQR 5–8), with 13.3% (69/517) scored 10 (extremely sick).

One-third of the participants (36.6%, 191/522) reported they had had the mpox vaccine, 59.8% (312/522) had not had the mpox vaccine and 3.6% (19/522) were unsure. Compared with participants who were not PrEP users, PrEP users (aOR 3.08, 95% CI: 1.82–5.20) had higher odds of being vaccinated against mpox after adjusting for other potential confounders (Table 3). Furthermore, individuals with the following characteristics also had higher odds of being vaccinated against mpox: aged 35–44 years compared to those aged 18–24 years (aOR 2.61; 95% CI: 1.09–6.22), those who had completed certificates/diplomas/apprenticeships compared to those completed primary/secondary school (aOR 2.54; 95% CI: 1.11–5.81), those being recruited from sexual health clinic compared to community (aOR 1.79; 95% CI: 1.10–2.92), those who had an STI diagnosis in the past 12 months (aOR 1.80; 95% CI: 1.12–2.90) and those who had a good mpox knowledge compared to poor knowledge (aOR 4.05; 95% CI: 1.54–10.61). The Hosmer–Lemeshow test showed that there was no evidence of lack of fit in the multivariable logistic regression model (χ² = 266.94, P = 0.625) and the C-statistic of 0.796 suggested a high degree of model strength.

Of the 312 participants who did not have the mpox vaccine at the time of the survey, 68.3% (213/312) reported they intended to get vaccinated, 8.0% (25/312) reported they would not get vaccinated, 23.4% (73/312) were unsure whether they would get vaccinated, and 0.3% (1/312) preferred not to answer. Eighteen participants planned to have casual sex while travelling overseas (i.e. UK, Europe or North America) before 31 October 2022, and all (100%) intended to receive the mpox vaccine. The multivariable analysis showed that PrEP users (aOR = 3.40; 95% CI: 1.21–9.53) and those who had attended SOPV in the past 12 months (aOR = 3.84; 95% CI: 1.10–13.44) had higher odds of having the intention to receive the mpox vaccine (Table 4).

Fig. 1 shows that a substantial proportion of participants would either reduce or stop some sexual activities to prevent mpox. Most reported they would reduce having sex with casual partners (53.9%, 280/519), stop having chemsex (49.8%, 254/510), stop attending SOPV (49.3%, 253/513), and stop having group sex (45.3%, 233/514). One-quarter (26.2%, 134/512) reported they would increase condom use for anal sex but half (51.2%, 262/512) would not change.

Fig. 1.

Proportion of study participants who would change their sexual practices because of the mpox outbreak.

During the study period, 60.9% (42/69) of the mpox cases in Victoria were diagnosed at MSHC. The weekly mpox cases diagnosed at MSHC peaked in late July and August, and it dropped significantly in early September after the implementation of the first phase of mpox vaccination program in mid-August (Fig. 2).

Fig. 2.

Weekly confirmed mpox cases diagnosed at the Melbourne Sexual Health Centre, 20 June−30 October 2022.

Discussion

This cross-sectional study showed more than two-thirds of unvaccinated MSM intended to receive the mpox vaccine. Our data has shown that the majority of MSM had good knowledge of mpox (i.e. averaging 10 questions correct out of 12). The good knowledge and high awareness of mpox reflect the success of timely online public health education, messaging and lay media coverage, and we found that having a good knowledge of mpox is the leading factor that is associated with mpox vaccination uptake. However, we found that the perceived severity of mpox was relatively high in our study compared to what clinical reports indicate about disease severity and this may be associated with the dissemination of misinformation through social media platforms.^38,39 The high proportion of MSM who were willing to reduce their sexual risk anecdotally may have contributed to fewer mpox cases given reductions occurred before substantial vaccination had occurred.

Cases of human-to-human transmission of mpox increased rapidly among the MSM community in several non-endemic European countries from May 2022 but declines in the number of cases in many countries began before substantial vaccine doses were given. For example, in the US, there was already a large decline in mpox cases at the beginning of August but their vaccination program was only rolled out from early July with a peak of uptake in mid-August.^40–43 Similarly in the UK, mpox cases began to decline around mid-July but vaccinations were only rolled out from late June with a peak of uptake in late July.^44,45 Lastly in Australia, cases declined in late August but the vaccination program only started in mid/late August.⁴⁰

The rapid increase and decline of mpox cases could be explained by several factors that may have preceded substantial vaccination coverage in the general MSM population. First, mpox vaccine uptake may have been highly concentrated in high-risk individuals and therefore vaccination may have had a more significant effect than would be expected from the relatively low initial coverage in general MSM population. It is estimated that the basic reproduction number (R₀) for the 2022 mpox outbreak is approximately 1.39 (95% CI: 1.37–1.42),⁴⁶ meaning one infected person can infect, on average, 1.4 new people. The herd immunity threshold can also be estimated by the –equation 1 – 1/R₀.⁴⁷ Based on the estimated R₀ from previous studies, it is estimated that at least 28% (i.e. 1 – 1/1.39 = 0.28) of the population needs to be vaccinated to end the mpox outbreak. In Victoria, the first phase of mpox vaccination program started in mid-August 2022 with a limited stock of 3500 doses of mpox vaccines, suggesting <10% of gay men living in Victoria would be able to access the mpox vaccines (i.e. estimated 36 000 gay men living in Victoria).^15,48 Our study has shown that 37% of the study participants who were at substantial STI risk, had been vaccinated against mpox, and vaccinated participants are over-represented among those who had an STI and attended SOPV in the past 12 months, which were the eligibility criteria for the first phase of mpox vaccination although these individual’s risk factors are not associated with vaccination uptake in the multivariable analysis. A UK-based mathematical model has also predicted substantial second waves of mpox in the absence of mpox vaccination and reversion in sexual practices;⁴⁹ therefore, continuing to vaccinate at-risk populations is important to prevent a rebound of mpox cases.

Second, the willingness to change sexual practices may also explain the rapid reductions in mpox cases. Our findings showed that the majority of MSM would consider harm reduction strategies (i.e. reducing or stopping at-risk sexual practices such as group sex, casual sex, chemsex and attending SOPV) to prevent mpox. This is also consistent with the findings from a US study carried out in August 2022 among 797 MSM showing almost half reported reducing the number of sexual partners, one-time sexual partners, group sex, and meeting a partner for sex via a dating app or at a SOPV since the mpox outbreak;⁵⁰ while another half also reported they did not change their sexual practices but it is unclear whether these individuals have engaged in these activities before the mpox outbreak. Reducing the number of sexual partners (i.e. contact with susceptible or infected individuals) will reduce the R₀; and the magnitude of the intended reduction is likely to substantially reduce transmission. A US-based mathematical model has estimated that one-time sexual partners account for approximately 50% of mpox transmission among MSM; and a 40% reduction in one-time sexual partners could potentially delay the spread of the mpox outbreak and reduce the proportion of infected MSM by 20–31%.⁵¹ The willingness to reduce sexual risk practices may be due to the fear and anxiety of acquiring mpox.⁵² Numerous clinical pictures of people with an extreme presentation of mpox (particularly those with obvious rash lesions on the face) were disseminated through the media at the beginning of the outbreak. This might have created fear of catching mpox and thus changed practices to reduce the risk of contracting mpox. Similar observations in reducing sexual risk practices at the beginning of the AIDS epidemic in the 1980s were also noted and resulted in the reductions in other STIs.^22,53 Additionally, the stigma of the mpox outbreak reinforces the homophobic and racist stereotypes in the MSM community, particularly among those who are vaccinated or have been diagnosed with mpox.⁵⁴ Stigmatisation can be a major barrier for individuals to seek health care for mpox vaccination or treatment. Lessons learnt from past epidemic such as HIV can be applied to reduce stigma in mpox and protect the vulnerable community.⁵⁵

There is other evidence suggesting that the reproductive rate of STIs has been reduced by reductions in sexual practices. The UK noted that the reduction in mpox cases was temporally associated with declines in lymphogranuloma venereum and Shigella diagnoses suggesting that reductions in STI risk were driven by mpox cases.⁴⁴ Observations that the R₀ for mpox reduced as the epidemic progressed also support this observation.⁴⁴ It would be reasonable to assume however that the reductions in sexual risk were temporary and that the mpox vaccine roll-out will now be the principal reason that no relapse in the outbreak has occurred.

Third, it is possible only a relatively small core group was driving mpox transmission in Australia and that this small core group became immune from natural infection early in the epidemic. This possibility is supported by a Dutch-based mathematical modelling study has shown that the high infection-induced immunity due to core group is sufficient to fade out the mpox outbreak in the absence of mpox vaccination program.⁵⁶

There are several limitations to this study. First, participants were recruited from a convenience sample of MSM attending a sexual health service, connecting to social media or the LGBTQIA+ community. Individuals who have been vaccinated against mpox, are more concerned about mpox, more sexually active or have better sexual health knowledge and awareness might be more likely to participate and complete the survey. The high level of mpox vaccination in this group suggests that the early vaccination program appropriately targeted higher risk individuals. Second, recall bias and social desirability bias might have occurred of self-reported sexual practices and vaccination status.⁵⁷ Third, due to the limited stock of the vaccines, some individuals might not be eligible or have access to the mpox vaccines; however, we did not ask unvaccinated study participants whether they had issues or difficulties in accessing the mpox vaccines. Fourth, we asked participants whether they would change their sexual practices to prevent mpox infection, which reflects their intention or willingness to change rather than the actual behavioural changes.

Australian health departments and local community-based organisations released timely public health education and messaging about mpox to the community. The education and messaging included the mode of mpox transmission, mpox-related symptoms, prevention, treatment and vaccination. Our study suggests that the education and messaging together with the widespread media attention the outbreak received resulted in a small and brief mpox outbreak. Whether this was related to sufficient vaccine coverage of high-risk individuals, changes in sexual practices and risk or a combination of these factors is hard to determine. Digital media provide a convenient and easy access platform for people accessing related information and individuals may also rely on these platforms for health-related information.^58–60 However, fake news and misleading content can also be disseminated through these channels easily;^{38,39,61–63} and this misleading content not only affects individuals’ health related to the disease (e.g. vaccine hesitancy) but also their mental health (e.g. anxiety).^64–66 Leading health organisations or local health authorities should monitor these social media and remove harmful and misleading health information for future disease outbreaks or pandemics.³⁹ Lastly, culturally appropriate public health communication and messaging are important to reduce stigmatisation and discrimination about the disease or affected communities.^67,68

Data availability

The data that support this study are available in the article.

Conflicts of interest

EPFC is an Associate Editor of Sexual Health, but was blinded from the peer review process for this manuscript. The authors declare no other conflicts of interest.

Declaration of funding

EPFC and DAW are each supported by an Australian National Health and Medical Research Council (NHMRC) Emerging Leadership Investigator Grant (GNT1172873 and GNT1174555, respectively). CKF and CSB are each supported by an Australian NHMRC Leadership Investigator Grant (GNT1172900 and GNT1173361, respectively). JMT and MYC are supported by Australian National Health and Medical Research Council (NHMRC) Partner Project Grant (GNT2003399).

Author contributions

EPFC, RSS, CSB, MYC, DAW and CKF conceived and designed the study. EPFC performed data analyses and wrote the first draft of the manuscript. KM and FM were involved in study recruitment. FM designed the study materials. JMT extracted and reviewed the number of mpox cases at the Melbourne Sexual Health Centre. All authors provided data interpretation, revised the manuscript for intellectual content, and approved the final version of the manuscript. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.