Investigation of an Mpox Outbreak Affecting Many Vaccinated Persons in Chicago, Illinois—March 2023–June 2023

Abstract

Background

After months of few mpox cases, an increase in cases was reported in Chicago during May 2023, predominantly among fully vaccinated (FV) patients. We investigated the outbreak scope, differences between vaccinated and unvaccinated patients, and hypotheses for monkeypox virus (MPXV) infection after vaccination.

Methods

We interviewed patients and reviewed medical records to assess demographic, behavioral, and clinical characteristics; mpox vaccine status; and vaccine administration routes. We evaluated serum antibody levels after infection and compared patient viral genomes with MPXV sequences in available databases. We discussed potential vaccine compromise with partners who manufactured, handled, and administered the vaccine associated with breakthrough infections.

Results

During 18 March–27 June 2023, we identified 49 mpox cases; 57% of these mpox patients were FV. FV patients received both JYNNEOS doses subcutaneously (57%), intradermally (7%), or via heterologous administration (36%). FV patients had more median sex partners (3; interquartile range [IQR] = 1–4) versus not fully vaccinated patients (1; IQR = 1–2). Thirty-six of 37 sequenced specimens belonged to lineage B.1.20 of clade IIb MPXV, which did not demonstrate any amino acid changes relative to B.1, the predominant lineage from May 2022. Vaccinated patients demonstrated expected humoral antibody responses; none were hospitalized. No vaccine storage excursions were identified. Approximately 63% of people at risk for mpox in Chicago were FV during this period.

Conclusions

Our investigation indicated that cases were likely due to frequent behaviors associated with mpox transmission, even with relatively high vaccine effectiveness and vaccine coverage. Cases after vaccination might occur in similar populations.

mpox, vaccination, monkeypox virus, outbreak

A global mpox outbreak was detected in May 2022, primarily affecting gay, bisexual, and other men who have sex with men (MSM) [1]. On 1 August 2022, a peak of 646 cases was reported in the United States on a single day [2]. National prevention efforts included vaccination and public health harm reduction messaging to those at increased risk of monkeypox virus (MPXV) infection [3]. Approximately 1.2 million doses of JYNNEOS were administered, with varying vaccination coverage rates [4]. Survey data suggest that MSM modified sexual behaviors to protect themselves and their partners from mpox, including reducing 1-time sexual partnerships [5]. By December 2022, case counts decreased to a 7-day moving average of 16 cases per day and remained consistently low for months [6, 7].

Consistent with national trends, the Chicago Department of Public Health (CDPH) received only 6 reports of mpox during January 2023–March 2023 despite receiving 143 reports per week during the outbreak peak [8]. Unlike most US jurisdictions, vaccination coverage in Chicago was at the level that models suggested might prevent large outbreaks [9]; 63% of persons at risk for mpox in Cook County, Illinois (which includes Chicago and the outlying areas), were estimated to have immunity after partial or full vaccination or prior infection [4]. However, CDPH received an unusually high number of mpox reports from 17 April 2023 through 5 May 2023. At detection, the cluster comprised 13 infections; 9 had received 2 doses of the JYNNEOS vaccine [10]. A similar increase in cases among previously vaccinated persons had been identified in France in January 2023 [11]. Both clusters triggered substantial media attention and raised concerns about the duration of protection of the 2-dose JYNNEOS vaccine series [12]. We launched a multifaceted investigation to assess outbreak scope, differences between vaccinated and unvaccinated patients, and hypotheses for MPXV infection postvaccination.

METHODS

Case Investigation

We defined a case as signs or symptoms of mpox in a person with epidemiologic risk factors for mpox and laboratory detection. Laboratory confirmation of orthopoxvirus or monkeypox virus was conducted using polymerase chain reaction testing [13] of MPXV (confirmed cases) or orthopoxvirus (probable cases) from 18 March 2023 through 27 June 2023 [14]. Mpox patients were considered fully vaccinated (FV) if they received 2 doses of the JYNNEOS vaccine or 1 dose of ACAM2000 ≥2 before infection. ACAM2000 is the live replicating virus vaccine that is used to prevent orthopoxviruses but was minimally used during the 2022–2023 US mpox outbreak. We considered patients not fully vaccinated (NFV) if they received only 1 dose of JYNNEOS or no doses of JYNNEOS or ACAM2000. We abstracted information about clinical presentation; mpox vaccinations; sexually transmitted infections (STIs), which included primary and secondary syphilis, gonorrhea, and chlamydia, reported concurrently and in the prior 12 months; and treatment with tecovirimat from medical records and local, state, and national data registries [15]. We examined hospitalizations, tecovirimat [16] treatment, and the distribution of mucosal areas affected among patients to characterize mpox severity. We attempted to interview all patients who met the case definition for clinical illness, potential exposures, and sexual behaviors.

Laboratory Evaluations

After diagnostic confirmation, we sequenced MPXV DNA to determine relatedness of cluster sequences to each other and to publicly available MPXV isolates and to assess for mutations associated with increased transmission or pathogenicity [17]. Whole-genome sequence libraries were prepared using the PrimalSeq amplicon scheme and sequenced on NovaSeq6000 (Illumina) [18]. Consensus sequences were generated using the TheiaCoV_Illumina_PE pipeline and reference MT903345. We generated a phylogenetic tree that included cluster patients and contextual isolates randomly sampled from other contemporaneous B.1.20 (n = 24) and US B.1 sequences (n = 13) in 2022–2023 using Nextstrain and IQ-TREE (see Supplementary Appendix for isolates).

We assessed serum antibody responses after vaccination and recovery from mpox to ensure patients mounted expected immune responses. The single dilution immunoglobulin (Ig) G and IgM enzyme-linked immunosorbent assay (ELISA) was used for nonquantitative assays. There is a good correlation between the optical density minus a cut off value (OD-COV) result and end point titers. Consenting patients provided a blood serum sample in exchange for a $100 gift card incentive. Serum was tested for anti-orthopoxvirus IgG and IgM antibodies using ELISA [19]. OD-COVs with IgG > 0.0 and IgM > 0.04 were considered positive.

Vaccine Product Investigation

We assessed the cold chain management of shipments and lots of vaccines distributed from the US Strategic National Stockpile (SNS), which supplements medical countermeasures needed by states, tribal nations, territories, and the largest metropolitan areas during public health emergencies [20], to CDPH and from CDPH to local healthcare providers. We interviewed key partners; facilities included 1 federally qualified health center, 2 academic health centers that provide off-site vaccination, 1 STI specialty clinic, 1 mobile clinic, and 1 private clinic. Interviews included 4 interviews with administrators and supply chain managers, 4 interviews with persons who vaccinated patients, and 2 joint interviews with administrators and vaccinators using a standardized tool. Interviews focused on potential temperature deviations in storage and transport and mishandling of vaccine during administration, including use of syringes filled before administration, use of punctured vials, and excessive exposure to heat or sunlight. We reviewed vaccine storage and administration procedures and inspected city vaccine storage sites.

Statistical Analyses

We examined descriptive statistics of demographic, behavioral, and clinical characteristics using the Pearson χ² test, t test statistics, or Fisher exact test to measure significance (P < .05). We estimated the Spearman rank correlation coefficient to compare the number of mutations in whole-genome sequencing. We analyzed data using SAS version 9.4.

ETHICS

This work was deemed a nonresearch public health surveillance activity (45 CFR 46.102(l)(2)). It was reviewed by the Centers for Disease Control and Prevention (CDC) and was conducted consistent with federal law and CDC policy (45 C.F.R. part 46, 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq).

RESULTS

Case Investigation

From 18 March 2023 through 27 June 2023, 46 confirmed and 3 probable mpox cases were reported to CDPH (Figure 1). Most cases were among cisgender males (43, 88%) who reported MSM contact (42, 86%). Patients’ median age was 33 years (interquartile range [IQR] = 29–38), and most identified as White, non-Hispanic, or Latino (22, 45%; Table 1). Twelve (25%) cases were among persons with human immunodeficiency virus (HIV, PWH); 10 (83%) had well-controlled HIV (CD4 count >200 cells/mm³ and viral load <200 copies/mL). Twenty-five (51%) patients had an STI ≤12 months before mpox diagnosis; 4 (8%) patients had a concurrent STI at mpox diagnosis. In the 3 weeks before symptom onset, 7 (16%) patients reported group sex, 14 (33%) reported anonymous sex, and 11 (23%) reported attending a large event, including a concert or festival. Of 15 (31%) patients who received tecovirimat, 4 (8%) were randomized to receive tecovirimat in the Study of Tecovirimat for Human Mpox Virus (STOMP) trial and 11 (22%) received tecovirimat due to clinical indication through the EA IND protocol or open label in the STOMP trial. One of the 2 hospitalized patients also received tecovirimat treatment. Eight patients had documented features aligned with CDC indications for its use [21]: ocular lesions (1), oral lesions (2), rectal lesions with painful or bloody defecation (4), and fungating lesions (1). Four of the 8 patients were PWH, 3 of whom had well-controlled HIV (CD4 count >500 cells/mm³, viral load <200 copies/ml) and were FV and 1 patient with advanced HIV who was unvaccinated.

Figure 1.

Epidemic curve (A) and vaccination timing of all mpox cases (B) and cases in this investigation (C).

Table 1.

Demographic and Clinical Characteristics of Mpox Patients in Chicago, 18 March 2023–27 June 2023

Characteristic	Overall (N = 49)	Fully Vaccinateda (n = 28)	Not Fully Vaccinatedb (n = 21)	P Valuec
Median age, y (IQR)	33 (29–38)	33.5 (30–40.5)	30 (28–36)	.1427d
Sex at birth				.4286e
Male	48 (98)	28 (100)	20 (95)
Female	1 (2)	0 (0)	1 (5)
Current gender identity				.3630e
Male	43 (88)	25 (89)	18 (86)
Transgender male	1 (2)	0 (0)	1 (5)
Other	1 (2)	0 (0)	1 (5)
Unknown	4 (8)	3 (11)	1 (5)
Race and ethnicity				.0254e
Asian, non-Latinx	1 (2)	1 (4)	0 (0)
Black, non-Latinx	11 (23)	2 (7)	9 (43)
White, non-Latinx	22 (45)	15 (54)	7 (33)
Latinx	9 (18)	6 (21)	3 (14)
Other, non-Latinx	5 (10)	4 (14)	1 (5)
Unknown	1 (2)	0 (0)	1 (5)
Sexual orientation				.2572e
Gay	34 (69)	22 (79)	12 (57)
Bisexual	5 (10)	1 (4)	4 (19)
Other	2 (4)	1 (4)	1 (5)
Unknown	8 (16)	4 (14)	4 (19)
Persons with human immunodeficiency virus	12 (25)	5 (18)	7 (33)	.2125f
Persons who reported concurrent STIsg	4 (8)	1 (4)	3 (13)	.3006e
Persons who reported an STI in the past 12 mg	25 (51)	15 (54)	10 (48)	.6800f
Number of vaccine doses
0	17 (35)	…	…
1	4 (8)	…	…
2	28 (57)	…	…
Median months since last vaccine dose (IQR)	9 (8–10)	9 (8–9.5)	9.5 (9–11)	.3193d
Median number of sex partners (IQR)h (n = 44)	2 (1–3)	3 (1–4)	1 (1–2)	.0271d
Persons who reported group sexh (n = 44)	7 (16)	5 (20)	2 (11)	.6801e
Persons who reported anonymous sexh (n = 44)	14 (33)	8 (32)	6 (32)	.9763e
Persons who reported attending an eventh (n = 44)	11 (23)	7 (28)	4 (21)	.7315e
Persons who received tecovirimat for mpox	15 (31)	6 (21)	9 (43)	.1483e

Abbreviations: IQR, interquartile range; STI, sexually transmitted infection.

^aPersons in this group received 2 doses of the JYNNEOS vaccine or 1 dose of ACAM2000 >2 weeks prior to symptom onset.

^bPersons in this group received either 1 dose of the JYNNEOS or no vaccine >2 weeks prior to symptom onset.

^cComparing fully vaccinated persons and not fully vaccinated persons.

^dt test statistic.

^eFisher exact χ² statistic.

^fPearson χ² statistic.

^gIncludes primary and secondary syphilis, gonorrhea, and chlamydia.

^hIn the 3 weeks prior to symptom onset.

In total, 28 (57%) patients were FV. Among FV patients, 1 received ACAM2000 administered abroad during the global outbreak. Of those who received JYNNEOS, 15 (54%) received homologous subcutaneous vaccinations, 10 (36%) with heterologous routes of administration, and 2 (7%) with homologous intradermal administrations. The timeline of vaccine administration was consistent with the peak of all vaccine doses administered in Chicago (Figure 1). Median time from last vaccine dose to specimen collection date was 9 months (IQR = 8–10; range, 5–12). Lesions affected the following mucosal areas: ocular (FV, 0 [0%]; NFV, 2 [12%]; P = .07), oral (FV, 3 [11%]; NFV, 2 [12%]; P = .95), genital (FV, 3 [11%]; NFV, 4 [24%]; P = .28), and rectal (FV, 9 [33%]; NFV, 1 [6%]; P = .03). Two patients were hospitalized; both were unvaccinated PWH who presented with painful skin lesions. One had advanced HIV (CD4 count <200 cells/mm³), fungating lesions, and bacterial superinfection. The other patient was virally suppressed (viral load <200  cells/mm³) and experienced oropharyngeal lesions with odynophagia.

Whole-Genome Sequencing

Isolates were obtained for whole-genome sequencing from 42 (86%) patient specimens. Thirty-seven had adequate genome coverage for analysis (>80%) [11], including 14 (38%) from FV patients and 23 (62%) from NFV patients.

Thirty-six sequences fell within a single phylogenetic clade, Mpox B.1 sublineage B.1.20, which was defined by Nextstrain on 1 August 2023 and includes these isolates and US ancestors from late 2022 (Figure 2) with no amino acid changes relative to the parent lineage B.1. No genetic differences were observed between MPXV sequences from vaccinated and unvaccinated patients, and sequences obtained from vaccinated patients were interspersed with sequences from unvaccinated patients (Figure 2). The single nonclustering sequence was identified as B.1.13 lineage and was a prolonged infection with initial onset of illness in December 2022.

Figure 2.

Phylogenetic tree of Chicago mpox isolates and random contextual US cases from 2022 to 2023. A phylogenetic tree including cluster patients and contextual isolates randomly sampled from other contemporaneous B.1.20 (n = 24) and US B.1 sequences (n = 13) in 2022–2023. Blue nodes represent Chicago cluster specimens, and yellow nodes represent contextual sequences. The tree was rooted on MPXV lineage A reference NC_063383, and lineage B subtree is isolated here. Node bootstrap support values are shown. The scale bar indicates the number of nucleotide mutations. Abbreviations: IL, Illinois; MN, Minnesota; NY, New York; TX, Texas.

Among all 36 B.1.20 isolates, 18 were identical, 16 were closely related (ie, 1–4 nucleotide mutations diverged from the identical specimens), and 2 were less closely related (ie, lacked 1–2 mutations shared by the identical sequences and contained 4–6 other unique mutations). The Chicago isolates diverged by 3 nucleotides from 2 genomes (undisclosed state) in March 2023 and diverged by 4 nucleotides (Texas) in 2022. Limited diversification within this clade was observed; identical genomes were obtained from specimens collected up to 10 weeks apart. Few amino acid mutations were identified within the B.1.20 Chicago cluster, and none occurred for MPXV protein VP37, which is associated with tecovirimat resistance [22].

Serologic Analysis

Ten FV and 3 NFV patients (all received 1 dose of JYNNEOS) had serological analysis. All specimens were positive for IgG antibodies (median IgG OD-COV = 1.28, IQR = 1.25–1.38), and 12 (92%) specimens were positive for IgM with a cutoff of 0.04 (median IgM OD-COV = 0.26, IQR = 0.19–0.49). IgM values did not differ for patients who received 1 (median IgM = 0.36, IQR = 0.15–0.58) compared with 2 JYNNEOS doses (median IgM = 0.25, IQR = 0.19–0.49; t test P = .59). The median time from mpox specimen collection to serological analysis was 21 days (IQR = 18–30; Figure 3).

Figure 3.

Serological analysis results (IgM) and days since mpox specimen collection by vaccination status. Abbreviations: IgM, immunoglobulin M; OD-COV, optical density minus a cutoff value.

Vaccine Product Investigation

All vaccines administered to this patient cluster were sent from the SNS from 3 June 2022 through 8 September 2022 and received in Chicago by 9 shipments from 3 June 2023 through 17 August 2023. These vaccines came from 6 lots that were sent to jurisdictions throughout the United States and were administered in Chicago from 1 July 2022 through 15 November 2022. Eighty-four percent of doses administered to these patients were from 2 lots that were used for 67% of all doses administered in Chicago and were widely distributed across the United States.

Throughout the chain of transport from SNS to CDPH to individual facilities, temperature deviations outside the recommended range of −25°C to −15°C while frozen and 2°C–8°C after being thawed were monitored as part of established cold chain management processes as for other vaccines. Excursions were identified using temperature monitoring devices that alert when a deviation occurs. A temperature excursion that occurred during transport from the SNS to Chicago was evaluated and deemed by all partners as unlikely to have affected product stability because the vials were still frozen upon receipt in Chicago. No temperature excursions were experienced while the vaccine was in city of Chicago custody, where it was stored in a central vaccine storage facility with automated active temperature monitoring with redundant alerts. No vaccine vials had physical damage upon receipt in Chicago or before distribution to health facilities.

In interviews with healthcare providers, we obtained information on vaccination conditions for 34 doses administered to patients: 23 (68%) doses were administered in a clinical setting, and 11 (32%) were administered at vaccine events outside of a clinical setting, including 2 (6%) doses administered outdoors. Storage temperatures were monitored and recorded consistently at facilities with no noted temperature excursions. One provider reported having coolers with temperature logs for transport to offsite vaccination events. Potential administration breaches were identified: administration in a room where ambient temperature exceeded 25°C (6% of doses), use of punctured vials (3%), and syringes filled before administration for longer than 2 minutes (6% of doses). However, these deviations were not specific to doses administered to affected patients.

DISCUSSION

After a thorough evaluation, we concluded that MPVX infections among FV persons were less likely to result in hospitalization, were associated with having more sexual partners in the 3 weeks before symptom onset, and involved viruses that exhibited no pathogenic differences in genome sequences. We did not identify clinical explanations for patients with infections after vaccination; available serological data showed no diminished immune response among these patients. Monitoring for vaccine temperature excursions and adjudicating findings should prevent use of potentially compromised vaccine; minor breaches in administration would be expected to have occurred nationwide. In either case, other clusters of infections were not reported; these factors were deemed unlikely to explain the outbreak. Sequencing results support that the outbreak comprised a single, dominant lineage. No genetic evidence is available to support adaptation of the virus to evade vaccine, improve transmissibility, or increase pathogenicity in this lineage.

Serology results suggest that a robust humoral immune response was mounted after infection in all patients given positive IgG results and IgM detection in 93% of patients. This indicates that there was likely no linking antibody immunodeficiency among these persons. Detection of IgM is known to be transient in most persons after vaccination and typically lasts for only a few months [23, 24]. Thus, IgM detection in 12 of 13 (92%) implicates recent MPXV infection as the source for this response. IgG responses were elevated in all FV and NFV relative to responses seen in unvaccinated persons after the 2003 US mpox outbreak [19] and similarly among persons for the current 2022 outbreak [manuscript in preparation]. This suggests that persons had mounted an anamnestic response associated with successful prior vaccination. However, we could not evaluate whether patients mounted a suboptimal response after initial vaccination because of a lack of longitudinal specimens.

Infections after full vaccination may occur in communities whose members exhibit behaviors associated with mpox transmission, such as having multiple sex partners during the 3 weeks before symptom onset and having 1-time partnerships, even when vaccination coverage is high. Smaller mpox clusters have been reported in other jurisdictions, including Los Angeles County, North Carolina, Hawaii, and King County, Washington [25]. Healthcare providers should include mpox in the differential diagnosis when sexually active patients present with mpox signs and symptoms, even if patients were previously vaccinated. A syndemic approach that holistically supports patients experiencing mpox, HIV, other STIs, homelessness, and mental health issues is crucial; PWH experience a greater risk of severe mpox disease [26], and mpox patients may be coinfected with other STIs or may have recently experienced another STI [27].

The JYNNEOS vaccine's estimated effectiveness against mpox disease is relatively high. In multiple, large, case-control studies across many US jurisdictions, effectiveness ranged from 66% to 88% [28–30]. These findings were also confirmed in the United Kingdom and Israel [31, 32]. Successful implementation of a vaccination strategy helped control the multicountry outbreak in 2022 [33]. The outbreak lineage B.1.20 is the predominant 2023 lineage observed in the United States and is distinct from another dominant 2023 lineage B.1.3/C.1, which is detected primarily in Asia [34, 35]. However, vaccines may not provide sterilizing immunity and do not prevent all infections from occurring. Mpox disease after previous vaccination or previous infection has been reported in other jurisdictions [11, 36, 37].

Vaccination benefits can include prevention of disease transmission and reduction in illness severity. In a small, global case series, clinical manifestations of mpox after previous vaccination were less severe [37]. California surveillance data showed that hospitalizations among vaccinated patients were significantly reduced compared with unvaccinated patients [38]. In Chicago, only 2 unvaccinated patients were hospitalized; both were PWH. Several patients with well-controlled HIV received tecovirimat; clinicians may have considered tecovirimat indicated despite no severe manifestations of mpox.

This investigation has multiple limitations. First, without data on immune status before the most recent MPXV infection, our analysis of immune responses can only identify persons who have mounted expected antibody response, and we could not evaluate the change in immunity or impact of prior immunity and durability of immune protection. These data also could not definitively differentiate immune responses attributable to infection from vaccine-induced immune response. Second, certain data are limited to self-report during patient interviews, which might be subject to bias, particularly for more sensitive questions about sexual behaviors, and recall bias. We were unable to characterize some reported sexual behaviors that were not included in patient interviews, such as 1-time partnerships in patients. Similarly, questions about vaccine handling and administration among vaccinators might be biased by recall bias or concerns about admitting fault. Finally, comparisons of patient severity based on receipt of tecovirimat might be more indicative of provider experience and procedures than of patient severity.

Global mpox cases continue to occur in countries without endemic mpox. The US Advisory Committee on Immunization Practices recently recommended inclusion of JYNNEOS vaccinations on the routine immunization schedule for persons at risk for mpox [39]. However, only 25% of persons eligible for vaccination in the United States are FV, and deaths among unvaccinated persons continue to occur. Although reassurances about vaccines were provided, other behavioral measures to prevent mpox were promoted in Chicago, including limiting the number of sexual partners and avoiding condomless, anonymous sexual exposure. CDPH engaged local community members and service providers who serve lesbian, gay, transgender, and queer persons in a communications and media campaign to share investigation findings and recommendations for mpox control. These measures may be applied in other jurisdictions during similar outbreak investigations. Future analyses of vaccine effectiveness by time since vaccination are also recommended to understand the risk for waning immunity in this population. However, confidence in the JYNNEOS vaccine should be strengthened through clinicians communicating the benefits of the 2-dose vaccination series and emphasizing that the global outbreak is ongoing.

Supplementary Data

Supplementary materials are available at Clinical Infectious Diseases online. Consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author.

Notes

Acknowledgments. The authors acknowledge Whitni Davidson, Nhien Wyn, Kimberly Wilkins, Faisal Minhaj, Dawn Broussard, and Ian Kracalik at the Centers for Disease Control and Prevention and Christopher Shields, Rebecca Pavlatos, Donna Peace, Van Quach, Usha Samala, Shamika Smith, Saadeh Ewaidah, Spencer Gorelick, and Stephanie Gretsch at the Chicago Department of Public Health for their contributions. They also appreciate the contributions of the clinicians and supply chain managers who were interviewed about vaccine maintenance. They thank Strategic National Stockpile, Bavarian Nordic, and City of Chicago vaccine experts for their knowledge of vaccine stability and cold chain maintenance. Finally, they appreciate the participation of patients with mpox in interviews and for providing serum samples.

Disclaimer. The contents presented here are those of the authors and do not necessarily represent the official views of or an endorsement by the Centers for Disease Control and Prevention, the US Department of Health and Human Services, or the US government.

Financial support. This work was supported by the Centers for Disease Control and Prevention of the Department of Health & Human Services.

Author notes

E. A. G. and T. H. share co-first authorship.

A. K. R. and I. T share co-senior authorship.

Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.