Real-world effectiveness of monkeypox vaccines: a systematic review

Scenarios of future mpox outbreaks among men who have sex with men: a modelling study based on cross-sectional seroprevalence data from the Netherlands, 2022

BackgroundFollowing the 2022-2023 mpox outbreak, crucial knowledge gaps exist regarding orthopoxvirus-specific immunity in risk groups and its impact on future outbreaks.AimWe combined cross-sectional seroprevalence studies in two cities in the Netherlands with mathematical modelling to evaluate scenarios of future mpox outbreaks among men who have sex with men (MSM).MethodsSerum samples were obtained from 1,065 MSM attending Centres for Sexual Health (CSH) in Rotterdam or Amsterdam following the peak of the Dutch mpox outbreak and the introduction of vaccination. For MSM visiting the Rotterdam CSH, sera were linked to epidemiological and vaccination data. An in-house developed ELISA was used to detect vaccinia virus (VACV)-specific IgG. These observations were combined with published data on serial interval and vaccine effectiveness to inform a stochastic transmission model that estimates the risk of future mpox outbreaks.ResultsThe seroprevalence of VACV-specific antibodies was 45.4% and 47.1% in Rotterdam and Amsterdam, respectively. Transmission modelling showed that the impact of risk group vaccination on the original outbreak was likely small. However, assuming different scenarios, the number of mpox cases in a future outbreak would be markedly reduced because of vaccination. Simultaneously, the current level of immunity alone may not prevent future outbreaks. Maintaining a short time-to-diagnosis is a key component of any strategy to prevent new outbreaks.ConclusionOur findings indicate a reduced likelihood of large future mpox outbreaks among MSM in the Netherlands under current conditions, but emphasise the importance of maintaining population immunity, diagnostic capacities and disease awareness.

T Cell Responses against Orthopoxviruses in HIV-Positive Patients

A global outbreak of predominantly sexually transmitted mpox infections, outside endemic regions, was reported in May 2022. Thereafter, risk groups were vaccinated against smallpox, a structurally related orthopoxvirus. In the current study, we analyzed T cell responses against peptides derived from orthopoxviruses in 33 HIV-positive patients after two vaccinations against smallpox and in 10 patients after mpox infection. We established an ELISpot assay, detecting either the secretion of the pro-inflammatory cytokine interferon (IFN)-γ or interleukin (IL)-2. After vaccination, 21 out of 33 patients (64%) showed specific IFN-γ secretion and 18 (55%) specific IL-2 secretion, defined as >3-fold higher specific value than negative control and at least 4 spots above the negative control. After mpox infection, all patients showed specific IFN-γ secretion and 7 out of 10 (70%) IL-2 secretion. In vaccinated patients, IFN-γ responses were significantly lower than in patients with mpox infection (median response 4.5 vs. 21.0 spots, p < 0.001). The same trend was observed for IL-2 responses. After mpox infection, IL-2 ELISpot results positively correlated with CD8+ T cells (p < 0.05). Thus, T cell responses were detectable in two thirds of HIV-positive patients after vaccination and were even more abundant and vigorous after mpox infection.

Transmission dynamics and effect of control measures on the 2022 outbreak of mpox among gay, bisexual, and other men who have sex with men in England: a mathematical modelling study

BACKGROUND

The 2022 global outbreak of mpox (formerly known as monkeypox) spread primarily among gay, bisexual, and other men who have sex with men (GBMSM), with the initial cluster being identified in England in May, 2022. Understanding its epidemiological characteristics and the reasons for its downturn in July, 2022, will help to control future outbreaks.

METHODS

We collated data for all diagnosed mpox cases (3621) from England from May 1, 2022, to Nov 16, 2022. Data from 75 individuals with mpox allowed estimation of the incubation period, while data from 121 case-contact pairs were used to estimate the serial interval. Six methods, including a structured dynamic compartmental transmission model, were used to estimate the basic reproduction number (R0). The structured model assumed all male individuals with mpox were GBMSM, who were then stratified into subgroups for those at low risk and high risk for mpox. This best fitting model was used to estimate the reduction in transmissibility, and the effective infectious period (before isolating), that resulted in the outbreak downturn, and the effect of vaccination initiated from June 27, 2022. Bayesian methods were used for parameter estimation and model calibration.

FINDINGS

Most cases occurred in men (3544 of 3621, 97·9%). The median incubation period for mpox was 6·90 days (95% credible interval [CrI] 4·08-20·21), and the serial interval was 8·82 days (5·22-25·81). R0 estimates ranged from 1·41 to 2·17. The structured transmission model estimated that 83·8% of infections (95% CrI 83·5-85·3) resulted from sexual partnerships with GBMSM individuals at high risk of mpox. The outbreak downturn probably resulted from a 44·5% reduction in the sexual partner rate among all GBMSM (24·9-55·8) and 20·0% reduction in the effective infectious period (4·1-33·9), preventing 165 896 infections (115 584-217 730). Vaccination marginally increased the number of infections prevented (166 081, 115 745-217 947), but minimised a resurgence in cases from January, 2023, and could have averted four times more infections if initiated earlier. Our findings were sensitive to assumptions regarding the vaccine's effectiveness and the GBMSM subgroup at high risk of mpox.

INTERPRETATION

The mpox outbreak in England probably resulted from high sexual partner rates among some GBMSM, with reductions in partner rates reversing the outbreak, and with vaccination minimising future outbreaks.

FUNDING

National Institute for Health Research (UK).

[Human monkeypox (Mpox)]

Until recently, human monkeypox (Mpox) were rarely observed outside of Africa, where the Mpox virus (MPXV) is endemic in some regions. In early May 2022, a global Mpox outbreak occurred. Crucial to this outbreak was human-to-human transmission during sexual activity. In particular, young men who have sex with men (MSM) became ill. In July 2022, this Mpox epidemic was declared a public health emergency of international concern by the World Health Organization. As of 26 September 2023, 90,618 confirmed cases of Mpox have been reported worldwide, with Germany accounting for around 3700 cases. The strongest increase in incidence occurred from May to mid-August 2022; since then, the number of cases has declined significantly as a result of intensive prevention efforts (education, vaccination). Currently, there are only sporadic, smaller outbreaks-in Germany (Berlin) most recently in August 2023. Despite the current calm epidemiological situation worldwide, isolated cases must therefore still be expected in Germany. The clinical picture of the "new" clade IIb-associated Mpox variant, which is mostly transmitted sexually from person to person, differs markedly from that of the "classical" Mpox (clades I and IIa), which, apart from rapidly breaking human infection chains, essentially occur as a zoonosis.

Lower rate of mpox vaccination hesitancy and medical consultation among Chinese men who have sex with men living with HIV in comparison with those living without HIV: A national observational study

This anonymous cross-sectional study aimed to investigate the relationships between HIV infection and mpox-related focus issues among Chinese men who have sex with men (MSM). This study involved in 27 MSM social organizations and was conducted from July 31 to August 4, 2023. Mpox vaccination hesitancy was defined as the proportion of participants who expressed unwillingness to receive self-funded and free vaccines. Logistic regression models were employed to estimate odds ratios (OR) and 95% confidence interval (95%CI). Of 7196 MSMs, the prevalence of mpox differed between people living with HIV (PLWH) (1.04%, 20/1920) and people living without HIV (PLWoH) (0.55%, 29/5276) (P = .037). However, after adjusting for all covariates, there was no significant association between HIV status and mpox (aOR = 1.17; 95%CI = 0.58, 2.39; P = .658). Furthermore, the crude rates of vaccination hesitation (PLWoH: 5.91%, PLWH: 4.11%; P = .004) and consultation hesitation (PLWoH: 16.22%, PLWH: 10.78%; P < .001) were both lower in the PLWH. Compared with PLWoH, PLWH had lower odds ratios of vaccination hesitation (aOR = 0.70; 95%CI = 0.53, 0.92; P = .011) and consultation hesitation (aOR = 0.74; 95%CI = 0.60, 0.90; P = .003) among MSM. The estimate of association between HIV status and consultation hesitation was even smaller among MSM who reported hepatitis C infection or uncertainty (aOR = 0.30; 95%CI = 0.15, 0.56), compared with those without hepatitis C (aOR = 0.73; 95%CI = 0.60, 0.89) (P for interaction = .037). MSM living with HIV in China demonstrated a greater willingness to accept mpox vaccination and medical consultation. In the future, it is recommended that medical institutions establish good medical environment to control the mpox epidemic, especially for PLWH.