Serologic responses to the MVA-based JYNNEOS mpox vaccine in a cohort of participants from the District of Columbia (D.C.).

We assessed early antibody responses after two doses of JYNNEOS (IMVANEX) mpox vaccine in the District of Columbia (D.C.) in persons at high risk for mpox without characteristic lesions or rash. Participants with PCR mpox negative specimens (oral swab, blood, and/or rectal swab) on the day of receipt of the first vaccine dose and who provided a baseline (day 0) serum sample and at least one serum sample at âˆ¼28, ∼42-56 days, or 180 days post vaccination were included in this analysis. Orthopoxvirus (OPXV)-specific IgG and IgM ELISAs and neutralizing antibody titers were performed, and longitudinal serologic responses were examined. Based on participants' IgG and IgM antibody levels at baseline, they were categorized as naïve or non-naïve. Linear mixed effects regression models were conducted to determine if IgG antibody response over time varied by age, sex, HIV status, and route of administration for both naïve and non-naïve participants. Among both naïve and non-naïve participants IgG seropositivity rates increased until day 42-56, with 89.4 % of naïve and 92.1 % of non-naïve participants having detectable IgG antibodies. The proportion of naive participants with detectable IgG antibodies declined by day 180 (67.7 %) but remained high among non-naïve participants (94.4 %). Neutralizing antibody titers displayed a similar pattern, increasing initially post vaccination but declining by day 180 among naïve participants. There were no significant serologic response differences by age, sex, or HIV status. Serologic response did vary by route of vaccine administration, with those receiving a combination of intradermal and subcutaneous doses displaying significantly higher IgG values than those receiving both doses intradermally. These analyses provide initial insights into the immunogenicity of a two-dose JYNNEOS PEP regimen in individuals at high risk of mpox exposure in the United States.

Examination of SARS-CoV-2 serological test results from multiple commercial and laboratory platforms with an in-house serum panel.

Severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) is a novel human coronavirus that was identified in 2019. SARS-CoV-2 infection results in an acute, severe respiratory disease called coronavirus disease 2019 (COVID-19). The emergence and rapid spread of SARS-CoV-2 has led to a global public health crisis, which continues to affect populations across the globe. Real time reverse transcription polymerase chain reaction (rRT-PCR) is the reference standard test for COVID-19 diagnosis. Serological tests are valuable tools for serosurveillance programs and establishing correlates of protection from disease. This study evaluated the performance of one in-house enzyme linked immunosorbent assay (ELISA) utilizing the pre-fusion stabilized ectodomain of SARS-CoV-2 spike (S), two commercially available chemiluminescence assays Ortho VITROS Immunodiagnostic Products Anti-SARS-CoV-2 Total Reagent Pack and Abbott SARS-CoV-2 IgG assay and one commercially available Surrogate Virus Neutralization Test (sVNT), GenScript USA Inc., cPass SARS-CoV-2 Neutralization Antibody Detection Kit for the detection of SARS-CoV-2 specific antibodies. Using a panel of rRT-PCR confirmed COVID-19 patients' sera and a negative control group as a reference standard, all three immunoassays demonstrated high comparable positivity rates and low discordant rates. All three immunoassays were highly sensitive with estimated sensitivities ranging from 95.4-96.6 %. ROC curve analysis indicated that all three immunoassays had high diagnostic accuracies with area under the curve (AUC) values ranging from 0.9698 to 0.9807. High positive correlation was demonstrated among the conventional microneutralization test (MNT) titers and the sVNT inhibition percent values. Our study indicates that independent evaluations are necessary to optimize the overall utility and the interpretation of the results of serological tests. Overall, we demonstrate that all serological tests evaluated in this study are suitable for the detection of SARS-CoV-2 antibodies.

How the Orthodox Features of Orthopoxviruses Led to an Unorthodox Mpox Outbreak: What We've Learned, and What We Still Need to Understand.

Orthopoxviruses have repeatedly confounded expectations in terms of the clinical illness they cause and their patterns of spread. Monkeypox virus (MPXV), originally characterized in the late 1950s during outbreaks among captive primates, has been recognized since the 1970s to cause human disease (mpox) in West and Central Africa, where interhuman transmission has largely been associated with nonsexual, close physical contact. In May 2022, a focus of MPXV transmission was detected, spreading among international networks of gay, bisexual, and other men who have sex with men. The outbreak grew in both size and geographic scope, testing the strength of preparedness tools and public health science alike. In this article we consider what was known about mpox before the 2022 outbreak, what we learned about mpox during the outbreak, and what continued research is needed to ensure that the global public health community can detect, and halt further spread of this disease threat.

Tecovirimat Resistance in Mpox Patients, United States, 2022-2023.

During the 2022 multinational outbreak of monkeypox virus (MPXV) infection, the antiviral drug tecovirimat (TPOXX; SIGA Technologies, Inc., https://www.siga.com) was deployed in the United States on a large scale for the first time. The MPXV F13L gene homologue encodes the target of tecovirimat, and single amino acid changes in F13 are known to cause resistance to tecovirimat. Genomic sequencing identified 11 mutations previously reported to cause resistance, along with 13 novel mutations. Resistant phenotype was determined using a viral cytopathic effect assay. We tested 124 isolates from 68 patients; 96 isolates from 46 patients were found to have a resistant phenotype. Most resistant isolates were associated with severely immunocompromised mpox patients on multiple courses of tecovirimat treatment, whereas most isolates identified by routine surveillance of patients not treated with tecovirimat remained sensitive. The frequency of resistant viruses remains relatively low (<1%) compared with the total number of patients treated with tecovirimat.

Prevalence of Undiagnosed Monkeypox Virus Infections during Global Mpox Outbreak, United States, June-September 2022.

Since May 2022, mpox has been identified in 108 countries without endemic disease; most cases have been in gay, bisexual, or other men who have sex with men. To determine number of missed cases, we conducted 2 studies during June-September 2022: a prospective serologic survey detecting orthopoxvirus antibodies among men who have sex with men in San Francisco, California, and a retrospective monkeypox virus PCR testing of swab specimens submitted for other infectious disease testing among all patients across the United States. The serosurvey of 225 participants (median age 34 years) detected 18 (8.0%) who were orthopoxvirus IgG positive and 3 (1.3%) who were also orthopoxvirus IgM positive. The retrospective PCR study of 1,196 patients (median age 30 years; 54.8% male) detected 67 (5.6%) specimens positive for monkeypox virus. There are likely few undiagnosed cases of mpox in regions where sexual healthcare is accessible and patient and clinician awareness about mpox is increased.

Monkeypox virus-infected individuals mount comparable humoral immune responses as Smallpox-vaccinated individuals.

In early 2022, a cluster of monkeypox virus (MPXV) infection (mpox) cases were identified within the UK with no prior travel history to MPXV-endemic regions. Subsequently, case numbers exceeding 80,000 were reported worldwide, primarily affecting gay, bisexual, and other men who have sex with men (GBMSM). Public health agencies worldwide have offered the IMVANEX Smallpox vaccination to these individuals at high-risk to provide protection and limit the spread of MPXV. We have developed a comprehensive array of ELISAs to study poxvirus-induced antibodies, utilising 24 MPXV and 3 Vaccinia virus (VACV) recombinant antigens. Panels of serum samples from individuals with differing Smallpox-vaccine doses and those with prior MPXV infection were tested on these assays, where we observed that one dose of Smallpox vaccination induces a low number of antibodies to a limited number of MPXV antigens but increasing with further vaccination doses. MPXV infection induced similar antibody responses to diverse poxvirus antigens observed in Smallpox-vaccinated individuals. We identify MPXV A27 as a serological marker of MPXV-infection, whilst MPXV M1 (VACV L1) is likely IMVANEX-specific. Here, we demonstrate analogous humoral antigen recognition between both MPXV-infected or Smallpox-vaccinated individuals, with binding to diverse yet core set of poxvirus antigens, providing opportunities for future vaccine (e.g., mRNA) and therapeutic (e.g., mAbs) design.

Antiviral activities of two nucleos(t)ide analogs against vaccinia, mpox, and cowpox viruses in primary human fibroblasts.

Many poxviruses are significant human and animal pathogens, including viruses that cause smallpox and mpox (formerly monkeypox). Identifying novel and potent antiviral compounds is critical to successful drug development targeting poxviruses. Here we tested two compounds, nucleoside trifluridine, and nucleotide adefovir dipivoxil, for antiviral activities against vaccinia virus (VACV), mpox virus (MPXV), and cowpox virus (CPXV) in physiologically relevant primary human fibroblasts. Both compounds potently inhibited the replication of VACV, CPXV, and MPXV (MA001 2022 isolate) in plaque assays. In our recently developed assay based on a recombinant VACV expressing secreted Gaussia luciferase, they both exhibited high potency in inhibiting VACV replication with EC50s in the low nanomolar range. In addition, both trifluridine and adefovir dipivoxil inhibited VACV DNA replication and downstream viral gene expression. Our results characterized trifluridine and adefovir dipivoxil as strong poxvirus antiviral compounds and further validate the VACV Gaussia luciferase assay as a highly efficient and reliable reporter tool for identifying poxvirus inhibitors. Given that both compounds are FDA-approved drugs, and trifluridine is already used to treat ocular vaccinia, further development of trifluridine and adefovir dipivoxil holds great promise in treating poxvirus infections, including mpox.

Clinical characterization and placental pathology of mpox infection in hospitalized patients in the Democratic Republic of the Congo.

We describe the results of a prospective observational study of the clinical natural history of human monkeypox (mpox) virus (MPXV) infections at the remote L'Hopital General de Reference de Kole (Kole hospital), the rainforest of the Congo River basin of the Democratic Republic of the Congo (DRC) from March 2007 until August 2011. The research was conducted jointly by the Institute National de Recherche Biomedical (INRB) and the US Army Medical Research Institute of Infectious Diseases (USAMRIID). The Kole hospital was one of the two previous WHO Mpox study sites (1981-1986). The hospital is staffed by a Spanish Order of Catholic Nuns from La Congregation Des Soeurs Missionnaires Du Christ Jesus including two Spanish physicians, who were members of the Order as well, were part of the WHO study on human mpox. Of 244 patients admitted with a clinical diagnosis of MPXV infection, 216 were positive in both the Pan-Orthopox and MPXV specific PCR. The cardinal observations of these 216 patients are summarized in this report. There were three deaths (3/216) among these hospitalized patients; fetal death occurred in 3 of 4 patients who were pregnant at admission, with the placenta of one fetus demonstrating prominent MPXV infection of the chorionic villi. The most common complaints were rash (96.8%), malaise (85.2%), sore throat (78.2%), and lymphadenopathy/adenopathy (57.4%). The most common physical exam findings were mpox rash (99.5%) and lymphadenopathy (98.6%). The single patient without the classic mpox rash had been previously vaccinated against smallpox. Age group of less than 5 years had the highest lesion count. Primary household cases tended to have higher lesion counts than secondary or later same household cases. Of the 216 patients, 200 were tested for IgM & IgG antibodies (Abs) to Orthopoxviruses. All 200 patients had anti-orthopoxvirus IgG Abs; whereas 189/200 were positive for IgM. Patients with hypoalbuminemia had a high risk of severe disease. Patients with fatal disease had higher maximum geometric mean values than survivors for the following variables, respectively: viral DNA in blood (DNAemia); maximum lesion count; day of admission mean AST and ALT.

Possible Undetected Mpox Infection Among Persons Accessing Homeless Services and Staying in Encampments - San Francisco, California, October-November 2022.

Monkeypox (mpox) is a disease caused by an Orthopoxvirus. The 2022 multinational outbreak, which began in May 2022, has spread primarily by close skin-to-skin contact, including through sexual contact. Persons experiencing homelessness have been disproportionately affected by severe mpox (1). However, mpox prevalence and transmission pathways among persons experiencing homelessness are not known, and persons experiencing homelessness have not been specifically recommended to receive mpox vaccine during the 2022 outbreak (2,3). During October 25-November 3, 2022, a CDC field team conducted an orthopoxvirus seroprevalence survey among persons accessing homeless services or staying in encampments, shelters, or permanent supportive housing in San Francisco, California that had noted at least one case of mpox or served populations at risk. During field team visits to 16 unique sites, 209 participants completed a 15-minute survey and provided a blood specimen. Among 80 participants aged <50 years who did not report smallpox or mpox vaccination or previous mpox infection, two (2.5%) had detectable antiorthopoxvirus immunoglobulin (Ig) G antibody. Among 73 participants who did not report mpox vaccination or previous mpox infection and who were tested for IgM, one (1.4%) had detectable antiorthopoxvirus IgM. Together, these results suggest that three possible undetected mpox infections occurred among a sample of persons experiencing homelessness, highlighting the need to ensure that community outreach and prevention interventions, such as vaccination, are accessible to this population.

Antiviral activities of two nucleos(t)ide analogs against vaccinia and mpox viruses in primary human fibroblasts.

Many poxviruses are significant human and animal pathogens, including viruses that cause smallpox and mpox. Identification of inhibitors of poxvirus replication is critical for drug development to manage poxvirus threats. Here we tested two compounds, nucleoside trifluridine and nucleotide adefovir dipivoxil, for antiviral activities against vaccinia virus (VACV) and mpox virus (MPXV) in physiologically relevant primary human fibroblasts. Both trifluridine and adefovir dipivoxil potently inhibited replication of VACV and MPXV (MA001 2022 isolate) in a plaque assay. Upon further characterization, they both conferred high potency in inhibiting VACV replication with half maximal effective concentrations (EC 50 ) at low nanomolar levels in our recently developed assay based on a recombinant VACV secreted Gaussia luciferase. Our results further validated that the recombinant VACV with Gaussia luciferase secretion is a highly reliable, rapid, non-disruptive, and simple reporter tool for identification and chracterization of poxvirus inhibitors. Both compounds inhibited VACV DNA replication and downstream viral gene expression. Given that both compounds are FDA-approved drugs, and trifluridine is used to treat ocular vaccinia in medical practice due to its antiviral activity, our results suggest that it holds great promise to further test trifluridine and adefovir dipivoxil for countering poxvirus infection, including mpox.

Design and Optimization of a Monkeypox virus Specific Serological Assay.

Monkeypox virus (MPXV), a member of the Orthopoxvirus (OPXV) genus, is a zoonotic virus, endemic to central and western Africa that can cause smallpox-like symptoms in humans with fatal outcomes in up to 15% of patients. The incidence of MPXV infections in the Democratic Republic of the Congo, where the majority of cases have occurred historically, has been estimated to have increased as much as 20-fold since the end of smallpox vaccination in 1980. Considering the risk global travel carries for future disease outbreaks, accurate epidemiological surveillance of MPXV is warranted as demonstrated by the recent Mpox outbreak, where the majority of cases were occurring in non-endemic areas. Serological differentiation between childhood vaccination and recent infection with MPXV or other OPXVs is difficult due to the high level of conservation within OPXV proteins. Here, a peptide-based serological assay was developed to specifically detect exposure to MPXV. A comparative analysis of immunogenic proteins across human OPXVs identified a large subset of proteins that could potentially be specifically recognized in response to a MPXV infection. Peptides were chosen based upon MPXV sequence specificity and predicted immunogenicity. Peptides individually and combined were screened in an ELISA against serum from well-characterized Mpox outbreaks, vaccinee sera, and smallpox sera collected prior to eradication. One peptide combination was successful with ~86% sensitivity and ~90% specificity. The performance of the assay was assessed against the OPXV IgG ELISA in the context of a serosurvey by retrospectively screening a set of serum specimens from the region in Ghana believed to have harbored the MPXV-infected rodents involved in the 2003 United States outbreak.

Fatal Human Rabies Infection With Suspected Host-Mediated Failure of Post-Exposure Prophylaxis Following a Recognized Zoonotic Exposure-Minnesota, 2021.

BACKGROUND: No human rabies post-exposure prophylaxis (PEP) failure has been documented in the United States using modern cell culture-based vaccines. In January 2021, an 84-year-old male died from rabies 6 months after being bitten by a rabid bat despite receiving timely rabies PEP. We investigated the cause of breakthrough infection. METHODS: We reviewed medical records, laboratory results, and autopsy findings and performed whole-genome sequencing (WGS) to compare patient and bat virus sequences. Storage, administration, and integrity of PEP biologics administered to the patient were assessed; samples from leftover rabies immunoglobulin were evaluated for potency. We conducted risk assessments for persons potentially exposed to the bat and for close patient contacts. RESULTS: Rabies virus antibodies present in serum and cerebrospinal fluid were nonneutralizing. Antemortem blood testing revealed that the patient had unrecognized monoclonal gammopathy of unknown significance. Autopsy findings showed rabies meningoencephalitis and metastatic prostatic adenocarcinoma. Rabies virus sequences from the patient and the offending bat were identical by WGS. No deviations were identified in potency, quality control, administration, or storage of administered PEP. Of 332 persons assessed for potential rabies exposure to the case patient, 3 (0.9%) warranted PEP. CONCLUSIONS: This is the first reported failure of rabies PEP in the Western Hemisphere using a cell culture-based vaccine. Host-mediated primary vaccine failure attributed to previously unrecognized impaired immunity is the most likely explanation for this breakthrough infection. Clinicians should consider measuring rabies neutralizing antibody titers after completion of PEP if there is any suspicion for immunocompromise.

Evidence of Mpox Virus Infection Among Persons Without Characteristic Lesions or Rash Presenting for First Dose of JYNNEOS Vaccine-District of Columbia, August 2022.

We assessed mpox virus prevalence in blood, pharyngeal, and rectal specimens among persons without characteristic rash presenting for JYNNEOS vaccine. Our data indicate that the utility of risk-based screening for mpox in persons without skin lesions or rash via pharyngeal swabs, rectal swabs, and/or blood is likely limited.

Use of Severe Acute Respiratory Syndrome Coronavirus 2 Antibody Tests by US Infectious Disease Physicians: Results of an Emerging Infections Network Survey, March 2022.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody tests have had limited recommended clinical application during the coronavirus disease 2019 (COVID-19) pandemic. To inform clinical practice, an understanding is needed of current perspectives of United States-based infectious disease (ID) physicians on the use, interpretation, and need for SARS-CoV-2 antibody tests. Methods: In March 2022, members of the Emerging Infections Network (EIN), a national network of practicing ID physicians, were surveyed on types of SARS-CoV-2 antibody assays ordered, interpretation of test results, and clinical scenarios for which antibody tests were considered. Results: Of 1867 active EIN members, 747 (40%) responded. Among the 583 who managed or consulted on COVID-19 patients, a majority (434/583 [75%]) had ordered SARS-CoV-2 antibody tests and were comfortable interpreting positive (452/578 [78%]) and negative (405/562 [72%]) results. Antibody tests were used for diagnosing post-COVID-19 conditions (61%), identifying prior SARS-CoV-2 infection (60%), and differentiating prior infection and response to COVID-19 vaccination (37%). Less than a third of respondents had used antibody tests to assess need for additional vaccines or risk stratification. Lack of sufficient evidence for use and nonstandardized assays were among the most common barriers for ordering tests. Respondents indicated that statements from professional societies and government agencies would influence their decision to order SARS-CoV-2 antibody tests for clinical decision making. Conclusions: Practicing ID physicians are using SARS-CoV-2 antibody tests, and there is an unmet need for clarifying the appropriate use of these tests in clinical practice. Professional societies and US government agencies can support clinicians in the community through the creation of appropriate guidance.

Revealing the complexity of vampire bat rabies "spillover transmission".

BACKGROUND: The term virus 'spillover' embodies a highly complex phenomenon and is often used to refer to viral transmission from a primary reservoir host to a new, naïve yet susceptible and permissive host species. Spillover transmission can result in a virus becoming pathogenic, causing disease and death to the new host if successful infection and transmission takes place. MAIN TEXT: The scientific literature across diverse disciplines has used the terms virus spillover, spillover transmission, cross-species transmission, and host shift almost indistinctly to imply the complex process of establishment of a virus from an original host (source/donor) to a naïve host (recipient), which have close or distant taxonomic or evolutionary ties. Spillover transmission may result in unsuccessful onward transmission, if the virus dies off before propagation. Alternatively, successful viral establishment in the new host can occur if subsequent secondary transmission among individuals of the same novel species and among other sympatric susceptible species occurred. As such, virus spillover transmission is a common yet highly complex phenomenon that encompasses multiple subtle stages that can be deconstructed to be studied separately to better understand the drivers of disease emergence. Rabies virus (RABV) is a well-documented viral pathogen which still inflicts heavy impact on humans, companion animals, wildlife, and livestock throughout Latin America due substantial spatial temporal and ecological-natural and expansional-overlap with several virus reservoir hosts. Thereby, the rabies disease system represents a robust avenue through which the drivers and uncertainties surrounding spillover transmission can be unravel at its different subtle stages to better understand how they may be affected by coarse, medium, and fine scale variables. CONCLUSIONS: The continued study of viral spillover transmission necessitates the elucidation of its complexities to better assess the cross-scale impacts of ecological forces linked to the propensity of spillover success. Improving capacities to reconstruct and predict spillover transmission would prevent public health impacts on those most at risk populations across the globe.

RABIES DIAGNOSIS AND RESPONSE TO VACCINATION IN SOUTHERN TAMANDUA (TAMANDUA TETRADACTYLA).

Rabies has rarely been described in Xenarthra, and rabies vaccine response has not been documented. A southern tamandua (Tamandua tetradactyla) presented with nonspecific clinical signs and was euthanatized. Subsequently, immunohistochemistry and RT-PCR confirmed a rabies diagnosis. Following these tests, a group of eight captive tamanduas were vaccinated with a killed rabies vaccine, and titers were measured at the time of vaccination and 23 d later. One animal had day 0 titers suggestive of previous vaccination or exposure. All animals had detectable neutralizing rabies virus antibody titers after vaccination, but one animal failed to meet the World Organization for Animal Health's definition for adequate vaccination (≥0.5 IU/ml), and two other animals had low antibody titers (0.56 and 0.6 IU/ml). Rabies should be considered as a possible cause of illness in tamanduas, and rabies vaccination may be a useful preventative measure when anthropic interaction through medical care or ambassador roles is occurring.

Human Rabies - Texas, 2021.

In late August 2021, a boy aged 7 years was bitten by a bat while he was playing outside his apartment home in Medina County, Texas. He informed his parents; however, no rabies postexposure prophylaxis (PEP) was sought because there were no visible bite marks, and the family was unaware that contact with a bat, including in the absence of visible bite marks, might cause rabies. Approximately 2 months later, the child was hospitalized for altered mental status, seizures, and hypersalivation and ultimately received a diagnosis of rabies. Experimental therapies were attempted; however, the child died 22 days after symptom onset. Fifty-seven persons who met criteria for suspected or known exposure to infectious secretions in this case were advised to consult with a medical provider about the need for rabies PEP in accordance with Advisory Committee on Immunization Practices (ACIP) guidelines (1). Rabies, an acute, progressive neuroencephalitis, is nearly always fatal. Although dogs are the most common source of human rabies deaths worldwide and account for an estimated 59,000 annual cases of human rabies globally (2), bats are the most common source of domestically acquired rabies in the United States and have been implicated in 31 (81.6%) of 38 human infections since 2000 (3). Attempts to prevent death or poor neurologic outcomes once rabies symptoms develop have been largely unsuccessful (4). Administration of rabies PEP, comprising rabies immunoglobulin and a series of doses of rabies vaccine, is critical to preventing rabies after an exposure; enhanced public education about the risk posed by bats, and the availability of PEP to prevent rabies, is needed.

Serological responses to the MVA-based JYNNEOS monkeypox vaccine in a cohort of participants from the Democratic Republic of Congo.

The current worldwide monkepox outbreak has reaffirmed the continued threat monkeypox virus (MPXV) poses to public health. JYNNEOS, a Modified Vaccinia Ankara (MVA)-based live, non-replicating vaccine, was recently approved for monkeypox prevention for adults at high risk of MPXV infection in the United States. Although the safety and immunogenicity of JYNNEOS have been examined previously, the clinical cohorts studied largely derive from regions where MPXV does not typically circulate. In this study, we assess the quality and longevity of serological responses to two doses of JYNNEOS vaccine in a large cohort of healthcare workers from the Democratic Republic of Congo (DRC). We show that JYNNEOS elicits a strong orthopoxvirus (OPXV)-specific antibody response in participants that peaks around day 42, or 2 weeks after the second vaccine dose. Participants with no prior history of smallpox vaccination or exposure have lower baseline antibody levels, but experience a similar fold-rise in antibody titers by day 42 as those with a prior history of vaccination. Both previously naïve and vaccinated participants generate vaccinia virus and MPXV-neutralizing antibody in response to JYNNEOS vaccination. Finally, even though total OPXV-specific IgG titers and neutralizing antibody titers declined from their peak and returned close to baseline levels by the 2-year mark, most participants remain IgG seropositive at the 2-year timepoint. Taken together, our data demonstrates that JYNNEOS vaccination triggers potent OPXV neutralizing antibody responses in a cohort of healthcare workers in DRC, a monkeypox-endemic region. MPXV vaccination with JYNNEOS may help ameliorate the disease and economic burden associated with monkeypox and combat potential outbreaks in areas with active virus circulation.

Orthopoxvirus Testing Challenges for Persons in Populations at Low Risk or Without Known Epidemiologic Link to Monkeypox - United States, 2022.

Since May 2022, approximately 20,000 cases of monkeypox have been identified in the United States, part of a global outbreak occurring in approximately 90 countries and currently affecting primarily gay, bisexual, and other men who have sex with men (MSM) (1). Monkeypox virus (MPXV) spreads from person to person through close, prolonged contact; a small number of cases have occurred in populations who are not MSM (e.g., women and children), and testing is recommended for persons who meet the suspected case definition* (1). CDC previously developed five real-time polymerase chain reaction (PCR) assays for detection of orthopoxviruses from lesion specimens (2,3). CDC was granted 510(k) clearance for the nonvariola-orthopoxvirus (NVO)-specific PCR assay by the Food and Drug Administration. This assay was implemented within the Laboratory Response Network (LRN) in the early 2000s and became critical for early detection of MPXV and implementation of public health action in previous travel-associated cases as well as during the current outbreak (4-7). PCR assays (NVO and other Orthopoxvirus laboratory developed tests [LDT]) represent the primary tool for monkeypox diagnosis. These tests are highly sensitive, and cross-contamination from other MPXV specimens being processed, tested, or both alongside negative specimens can occasionally lead to false-positive results. This report describes three patients who had atypical rashes and no epidemiologic link to a monkeypox case or known risk factors; these persons received diagnoses of monkeypox based on late cycle threshold (Ct) values ≥34, which were false-positive test results. The initial diagnoses were followed by administration of antiviral treatment (i.e., tecovirimat) and JYNNEOS vaccine postexposure prophylaxis (PEP) to patients' close contacts. After receiving subsequent testing, none of the three patients was confirmed to have monkeypox. Knowledge gained from these and other cases resulted in changes to CDC guidance. When testing for monkeypox in specimens from patients without an epidemiologic link or risk factors or who do not meet clinical criteria (or where these are unknown), laboratory scientists should reextract and retest specimens with late Ct values (based on this report, Ct ≥34 is recommended) (8). CDC can be consulted for complex cases including those that appear atypical or questionable cases and can perform additional viral species- and clade-specific PCR testing and antiorthopoxvirus serologic testing.