Modeling vaccination and control strategies for outbreaks of monkeypox at gatherings

Monkeypox Virus and Pregnancy

Human monkeypox (Mpox) is a zoonotic disease caused by monkeypox virus (MPXV) present in western Africa and exported sporadically worldwide. MPXV causes illness in individuals and pregnant women which constitute a population at risk with obstetrical and fetal complications including miscarriage, stillbirth and premature delivery. There are accumulated data suggesting a vertical transmission of MPXV from mother to fetus. This review provides an overview of the literature on MPXV infection in pregnant women with a specific focus on vertical transmission.

How mathematical modelling can inform outbreak response vaccination

Mathematical models are established tools to assist in outbreak response. They help characterise complex patterns in disease spread, simulate control options to assist public health authorities in decision-making, and longer-term operational and financial planning. In the context of vaccine-preventable diseases (VPDs), vaccines are one of the most-cost effective outbreak response interventions, with the potential to avert significant morbidity and mortality through timely delivery. Models can contribute to the design of vaccine response by investigating the importance of timeliness, identifying high-risk areas, prioritising the use of limited vaccine supply, highlighting surveillance gaps and reporting, and determining the short- and long-term benefits. In this review, we examine how models have been used to inform vaccine response for 10 VPDs, and provide additional insights into the challenges of outbreak response modelling, such as data gaps, key vaccine-specific considerations, and communication between modellers and stakeholders. We illustrate that while models are key to policy-oriented outbreak vaccine response, they can only be as good as the surveillance data that inform them.

An evaluation of the preprints produced at the beginning of the 2022 mpox public health emergency

BACKGROUND

Preprints are scientific articles that have not undergone the peer-review process. They allow the latest evidence to be rapidly shared, however it is unclear whether they can be confidently used for decision-making during a public health emergency. This study aimed to compare the data and quality of preprints released during the first four months of the 2022 mpox outbreak to their published versions.

METHODS

Eligible preprints (n = 76) posted between May to August 2022 were identified through an established mpox literature database and followed to July 2024 for changes in publication status. Quality of preprints and published studies was assessed by two independent reviewers to evaluate changes in quality, using validated tools that were available for the study design (n = 33). Tools included the Newcastle-Ottawa Scale; Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2); and JBI Critical Appraisal Checklists. The questions in each tool led to an overall quality assessment of high quality (no concerns with study design, conduct, and/or analysis), moderate quality (minor concerns) or low quality (several concerns). Changes in data (e.g. methods, outcomes, results) for preprint-published pairs (n = 60) were assessed by one reviewer and verified by a second.

RESULTS

Preprints and published versions that could be evaluated for quality (n = 25 pairs) were mostly assessed as low quality. Minimal to no change in quality from preprint to published was identified: all observational studies (10/10), most case series (6/7) and all surveillance data analyses (3/3) had no change in overall quality, while some diagnostic test accuracy studies (3/5) improved or worsened their quality assessment scores. Among all pairs (n = 60), outcomes were often added in the published version (58%) and less commonly removed (18%). Numerical results changed from preprint to published in 53% of studies, however most of these studies (22/32) had changes that were minor and did not impact main conclusions of the study.

CONCLUSIONS

This study suggests the minimal changes in quality, results and main conclusions from preprint to published versions supports the use of preprints, and the use of the same critical evaluation tools on preprints as applied to published studies, in decision-making during a public health emergency.

Estimating the relative importance of epidemiological and behavioural parameters for epidemic mpox transmission: a modelling study

BACKGROUND

Many European countries experienced outbreaks of mpox in 2022, and there was an mpox outbreak in 2023 in the Democratic Republic of Congo. There were many apparent differences between these outbreaks and previous outbreaks of mpox; the recent outbreaks were observed in men who have sex with men after sexual encounters at common events, whereas earlier outbreaks were observed in a wider population with no identifiable link to sexual contacts. These apparent differences meant that data from previous outbreaks could not reliably be used to parametrise infectious disease models during the 2022 and 2023 mpox outbreaks, and modelling efforts were hampered by uncertainty around key transmission and immunity parameters.

METHODS

We developed a stochastic, discrete-time metapopulation model for mpox that allowed for sexual and non-sexual transmission and the implementation of non-pharmaceutical interventions, specifically contact tracing and pre- and post-exposure vaccinations. We calibrated the model to case data from Berlin and used Sobol sensitivity analysis to identify parameters that mpox transmission is especially sensitive to. We also briefly analysed the sensitivity of the effectiveness of non-pharmaceutical interventions to various efficacy parameters.

RESULTS

We found that variance in the transmission probabilities due to both sexual and non-sexual transmission had a large effect on mpox transmission in the model, as did the level of immunity to mpox conferred by a previous smallpox vaccination. Furthermore, variance in the number of pre-exposure vaccinations offered was the dominant contributor to variance in mpox dynamics in men who have sex with men. If pre-exposure vaccinations were not available, both the accuracy and timeliness of contact tracing had a large impact on mpox transmission in the model.

CONCLUSIONS

Our results are valuable for guiding epidemiological studies for parameter ascertainment and identifying key factors for success of non-pharmaceutical interventions.

Simulating the impact of optimized prevention and control measures on the transmission of monkeypox in the United States: A model-based study

This study aimed to develop a modified susceptible-exposed-infected-recovered (SEIR) model to evaluate monkeypox epidemics in the United States and explore more optimized prevention and control measures. To further assess the impact of public health measures on the transmission of monkeypox, different intervention scenarios were developed based on the classic SEIR model, considering reducing contact, enhancing vaccination, diagnosis delay, and environmental transmission risk, respectively. We evaluated the impact of different measures by simulating their spread in different scenarios. During the simulation period, 8709 people were infected with monkeypox. The simulation analysis showed that: (1) the most effective measures to control monkeypox transmission during the early stage of the epidemic were reducing contact and enhancing vaccination, with cumulative infections at 51.20% and 41.90% of baseline levels, respectively; (2) shortening diagnosis time would delay the peak time of the epidemic by 96 days; and (3) the risk of environmental transmission of monkeypox virus was relatively low. This study indirectly proved the effectiveness of the prevention and control measures, such as reducing contact, enhancing vaccination, shortening diagnosis time, and low risk of environmental transmission, which also provided an important reference and containment experience for nonepidemic countries.

Human mpox: global trends, molecular epidemiology and options for vaccination

The eradication of smallpox and the cessation of vaccination have led to the growth of the susceptible human population to poxviruses. This has led to the increasing detection of zoonotic orthopoxviruses. Among those viruses, monkeypox virus (MPV) is the most commonly detected in Western and Central African regions. Since 2022, MPV is causing local transmission in newly affected countries all over the world. While the virus causing the current outbreak remains part of clade II (historically referred to as West African clade), it has a significant number of mutations as compared to other clade II sequences and is therefore referred to as clade IIb. It remains unclear whether those mutations may have caused a change in the virus phenotype. Vaccine effectiveness data show evidence of a high cross-protection of vaccines designed to prevent smallpox against mpox. These vaccines therefore represent a great opportunity to control human-to-human transmission, provided that their availability has short time-frames and that mistakes from the recent past (vaccine inequity) will not be reiterated.

A hierarchical intervention scheme based on epidemic severity in a community network

As there are no targeted medicines or vaccines for newly emerging infectious diseases, isolation among communities (villages, cities, or countries) is one of the most effective intervention measures. As such, the number of intercommunity edges ([Formula: see text]) becomes one of the most important factor in isolating a place since it is closely related to normal life. Unfortunately, how [Formula: see text] affects epidemic spread is still poorly understood. In this paper, we quantitatively analyzed the impact of [Formula: see text] on infectious disease transmission by establishing a four-dimensional [Formula: see text] edge-based compartmental model with two communities. The basic reproduction number [Formula: see text] is explicitly obtained subject to [Formula: see text] [Formula: see text]. Furthermore, according to [Formula: see text] with zero [Formula: see text], epidemics spread could be classified into two cases. When [Formula: see text] for the case 2, epidemics occur with at least one of the reproduction numbers within communities greater than one, and otherwise when [Formula: see text] for case 1, both reproduction numbers within communities are less than one. Remarkably, in case 1, whether epidemics break out strongly depends on intercommunity edges. Then, the outbreak threshold in regard to [Formula: see text] is also explicitly obtained, below which epidemics vanish, and otherwise break out. The above two cases form a severity-based hierarchical intervention scheme for epidemics. It is then applied to the SARS outbreak in Singapore, verifying the validity of our scheme. In addition, the final size of the system is gained by demonstrating the existence of positive equilibrium in a four-dimensional coupled system. Theoretical results are also validated through numerical simulation in networks with the Poisson and Power law distributions, respectively. Our results provide a new insight into controlling epidemics.

Monkeypox: a review of epidemiological modelling studies and how modelling has led to mechanistic insight

Human monkeypox (mpox) virus is a viral zoonosis that belongs to the Orthopoxvirus genus of the Poxviridae family, which presents with similar symptoms as those seen in human smallpox patients. Mpox is an increasing concern globally, with over 80,000 cases in non-endemic countries as of December 2022. In this review, we provide a brief history and ecology of mpox, its basic virology, and the key differences in mpox viral fitness traits before and after 2022. We summarize and critique current knowledge from epidemiological mathematical models, within-host models, and between-host transmission models using the One Health approach, where we distinguish between models that focus on immunity from vaccination, geography, climatic variables, as well as animal models. We report various epidemiological parameters, such as the reproduction number, R0, in a condensed format to facilitate comparison between studies. We focus on how mathematical modelling studies have led to novel mechanistic insight into mpox transmission and pathogenesis. As mpox is predicted to lead to further infection peaks in many historically non-endemic countries, mathematical modelling studies of mpox can provide rapid actionable insights into viral dynamics to guide public health measures and mitigation strategies.

An overview on Monkeypox, Current Paradigms and Advances in its Vaccination, Treatment and Clinical Management: Trends, Scope, Promise and Challenges

Monkeypox virus is an orthopoxvirus sharing the common genus with variola and vaccinia virus. Most of the monkeypox (MPX) cases had been reported from the central and west African region (the main endemic areas) prior to 2022 but there was a sudden outbreak in May, 2022 disseminating the infections to thousands of people even in non-endemic countries, posing a global public health emergency. MPX was considered a rae and neglected disease, however the 2022 MPX outbreaks in multiple countries attracted attention of worldwide researchers to pace up for carrying out researches on various aspects of MPXV including attempts to design and develop diagnostics, vaccines, drugs and therapeutics counteract MPX. Apart from being a zoonotic disease, the current outbreaks highlighted rapid human-to-human transmission of MPXV, besides the reverse zoonosis has also been documented with recent first report of human-to-dog transmission, urging a call for the importance of one health approach. Atypical and unusual disease manifestations as well asymptomatic MPXV infections have also been observed during 2022 MPX outbreak. The affected patients typically develop a rash resulting in a mild disease followed by recovery with some supportive care and use of antivirals such as tecovirimat, cidofovir and brincidofovir in severe disease cases. Modified vaccinia Ankara (MVA) vaccine with an excellent safety profile has been recommended to patients with higher risk exposure and immunocompromised individuals. Moreover, another vaccine the replication-competent vaccine (ACAM2000) could be a suitable alternative to MVA’s non-availability to some selective immunocompetent individuals. Current review highlights the salient aspects of management and treatment of monkeypox along with underlying promises in terms of therapeutics and a variety of challenges posed due to current global public health emergency situation to counteract MPX.

Saied A, Dhama K. Major Advances in Monkeypox Vaccine Research and Development – An Update

Monkeypox (MPX) is a zoonotic disease that is endemic to the western and central regions of Africa and it is caused by monkeypox virus (MPXV), which is classified as a member of the Poxviridae family, specifically the Chordopoxvirinae subfamily, and the Orthopoxvirus genus. The current multiregional outbreak of MPX, which started in May of 2022, has since swiftly spread across the globe and thus has been declared a global public health emergency by the World Health Organization (WHO). Protective immunity against MPXV can be achieved by administering a smallpox vaccination, as the two viruses share antigenic properties. Although smallpox was declared eradicated in 1980, the vaccine campaign was halted the following year, leaving the population with significantly less immunity than it had before. The potential for human-to-human transmission of MPXV has grown as a result. Due to the lack of a particular treatment for MPX infection, anti-viral medications initially designed for the smallpox virus are being employed. However, the prognosis for MPX may vary depending on factors like immunization history, pre-existing illnesses, and comorbidities, even though the majority of persons who develop MPX have a mild, self-limiting illness. Vaccines and antiviral drugs are being researched as potential responses to the latest 2022 MPX epidemic. The first-generation smallpox vaccinations maintained in national stockpiles of several countries are not recommended due to not meeting the current safety and manufacturing criteria, as stated by the WHO. Newer, safer (second- and third-generation) smallpox vaccines, such as JYNNEOSTM, which has been licensed for the prevention of MPX, are indicated as potentially useful in the interim guideline. Studies on vaccines and antiviral drugs are still being investigated as possible remedies to the recent MPX outbreak. This mini-review article serves as a retrospective look at the evolution of smallpox vaccines from their inception in the 1700s to the current trends up to the end of year 2022, specifically for developing monkeypox vaccines.