In vitro antimicrobial susceptibility data of global meropenem-resistant Acinetobacter baumannii isolates causing pneumonia: Data from the Antimicrobial Testing Leadership and Surveillance Program, 2014-2021, and re-estimations of susceptibility breakpoints and appropriate dosages of important antibiotics for pneumonia treatment.

OBJECTIVES: To evaluate the susceptibility of globally pneumonia-causing meropenem-resistant (MEM-R) Acinetobacter baumannii isolates against important antibiotics and estimate appropriate dosages of indicated antibiotics. METHODS: We extracted the 2014-2021 Antimicrobial Testing of Leadership Surveillance database regarding the susceptibility of MEM-R A. baumannii isolates causing pneumonia against important antibiotics. The susceptibility and carbapenemase-encoding gene (CPEG) data of pneumonia-causing MEM-R A. baumannii isolates from patients hospitalized in intensive care units of five major regions were analyzed. The susceptibility breakpoints (SBP) recommended by the Clinical and Laboratory Standards Institute (CLSI) in 2022, other necessary criteria [SBP of MIC for colistin, 2 mg/L, in the CLSI 2018; and cefoperazone-sulbactam (CFP-SUL), 16 mg/L], and the pharmacokinetic and pharmacodynamic data of indicated antibiotics were employed. RESULTS: Applying the aforementioned criteria, we observed the susceptible rates of colistin, minocycline, and CFP-SUL against the pneumonia-causing MEM-R A. baumannii isolates globally (n = 2905) were 93.2%, 69.1%, and 26.3%, respectively. Minocycline was significantly more active in vitro (MIC ≤4 mg/L) against the pneumonia-causing MEM-R A. baumannii isolates collected from North and South America compared to those from other regions (>90% vs. 58-72%). Additionally, blaOXA-23 and blaOXA-72 were the predominant CPEG in pneumonia-causing MEM-R A. baumannii isolates. CONCLUSIONS: After deliberative estimations, dosages of 200 mg minocycline intravenously every 12 h (SBP, 8 mg/L), 100 mg tigecycline intravenously every 12 h (SBP, 1 mg/L), and 160 mg nebulized colistin methanesulphonate every 8 h (SBP, 2 mg/L) are needed for the effective treatment of pneumonia-causing MEM-R A. baumannii isolates.

Impact of Antenatal SARS-CoV-2 Exposure on SARS-CoV-2 Neutralization Potency.

A pregnancy booster dose significantly reduces the risk and severity of COVID-19, and it is widely recommended. A prospective cohort study was conducted to compare the transplacental passage of maternal antibodies from vaccination or infection during three trimesters against both the vaccine-targeted Wuhan strain and the Omicron strain of SARS-CoV-2. Maternal-infant dyads from vaccinated mothers were collected between 6 June 2022 and 20 September 2022. We analyzed 38 maternal-infant dyads from mothers who had been infected with COVID-19 and 37 from mothers without any previous infection. Pregnant women who received their last COVID-19 vaccine dose in the third trimester exhibited the highest anti-spike protein antibody levels and neutralizing potency against both the Wuhan strain and Omicron BA.2 variant in their maternal and cord plasma. Both second- and third-trimester vaccination could lead to a higher level of neutralization against the Wuhan and Omicron strains. COVID-19 infection had a negative effect on the transplacental transfer ratio of SARS-CoV-2 antibodies. A booster dose during the second or third trimester is encouraged for the maximum transplacental transfer of humoral protection against COVID-19 for infants.

High ceftazidime-avibactam resistance among carbapenem-resistant Enterobacter species: Data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2014-2021.

OBJECTIVES: Trends in the susceptibility to ceftazidime-avibactam (CZA) and tigecycline (TGC) among Enterobacter species from different geographic areas are unknown.This study aimed to analyse the trends in CZA and TGC susceptibility changes across different continents from 2014 to 2021 utilizing Antimicrobial Testing Leadership and Surveillance (ATLAS) data. METHODS: A total of 23 669 isolates of Enterobacter species were collected over an 8-y period. RESULTS: The overall non-susceptibility rate of Enterobacter isolates to both CZA and TGC was 3.2%. India (16.5%), Guatemala (15.4%), and the Philippines (13.1%) exhibited the highest resistance to CZA. The increase in CZA resistance rates was particularly evident in Asia, with an increase from 4.0% to 8.3%, and in Latin America, from 1.5% to 5%. The non-susceptibility rate for TGC mildly increased in Africa/Middle East but decreased in other continents during the study period. The overall rate of carbapenem resistance increased from 2.9% in 2014-2017 to 4.3% in 2018-2021. Among carbapenem-resistant Enterobacter isolates, the CZA resistance rate was highest in Asia (87.4%), followed by Europe (69.2%) and Africa/Middle East (60.8%). Among the 380 Enterobacter isolates resistant to CZA and carbapenem, the most common genotype of carbapenemase genes was blaNDM (59.2%), followed by blaVIM (24.2%), blaOXA (4.2%), blaIMP (1.1%), and blaKPC (1.1%). The susceptibility of carbapenem-resistant Enterobacter to TGC remained high, with an overall susceptibility rate of 90%. CONCLUSIONS: The heterogeneous distribution of CZA resistance rates among different geographical regions highlights the divergent therapeutic options for drug-resistant Enterobacter species.

Global trends in nonsusceptibility rates of Escherichia coli isolates to meropenem and ceftazidime/avibactam: Data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2014-21.

OBJECTIVE: To understand the global changes in the nonsusceptibility rates of Escherichia coli to meropenem and ceftazidime-avibactam (CZA), we conducted a study using the Antimicrobial Testing Leadership and Surveillance database. METHODS: A total of 49 394 E. coli isolates were collected during the 8-year study period. RESULT: The countries with the highest nonsusceptible rates for meropenem were India (16.6%), followed by Pakistan (6.7%), Ukraine (5.4%), Qatar (5.3%), and Guatemala (3.2%). For CZA, the nonsusceptible rate was highest in India (15.6%), followed by Qatar (4.0%), Guatemala (3.9%), China (2.6%), and Thailand (2.5%). During the study period, the nonsusceptible rates of meropenem and CZA in E. coli increased in Asia, Latin America, and Africa/Middle East. Isolates from the medical ICU (odds ratio [OR], 4.62) and surgical ICU (OR, 3.98) were associated with a higher risk of CZA nonsusceptible rates. Compared to intestinal specimens, respiratory and genitourinary specimens had the highest OR (2.32 and 2.17) associated with CZA resistance. Further analysis of carbapenemase distribution showed an increase in the percentage of blaNDM-positive isolates and a decrease in blaKPC-positive isolates worldwide, especially in Latin America. Additionally, we observed a gradual decline in the prevalence of blaOXA-positive E. coli without concomitant carriage of metallo-ß-lactamase genes in the worldwide surveillance. CONCLUSIONS: Further surveillance is necessary to determine whether blaNDM -positive E. coli (i.e., CZA-resistant isolates) is increasing and leading to more superbugs spreading worldwide.

Socioeconomic Disparity in the Effect of SARS-CoV-2 on Outpatient Visits among People with Type 2 Diabetes in Taiwan.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak posed impact on healthcare. This study evaluated the effect of SARS-CoV-2 outbreak on the outpatient visits of patients with type 2 diabetes and determined the most affected groups. We analyzed Taiwan's National Health Insurance data, including 1,922,702 patients diagnosed with type 2 diabetes from 2018 to 2021. Group-based trajectory modelling identified four distinct outpatient visit patterns, namely, consistently high (Group 1, 74.2%), low-to-high (Group 2, 8.1%), high-to-low (Group 3, 6.0%) and consistently low (Group 4, 11.7%) utilization. Logistic regression was used to analyze correlations between trajectory types and patients' demographics and health statuses. Group 3 members had higher odds of being male [adjusted odds ratio (aOR) = 1.04, 95% confidence interval (CI) 1.03-1.05] and earning below 20,000 New Taiwan Dollar monthly (aOR = 1.29, 95% CI 1.26-1.31) than those in Group 1. However, they were less likely to be under 80 years old (aOR = 0.70-0.97), from lower median family income regions (aOR = 0.81-0.89) or possess a Charlson Comorbidity Index score > 2 (aOR = 0.67, 95% CI 0.66-0.68). Patients with lower income in affluent areas displayed the highest likelihood of falling into Group 3. Patients with type 2 diabetes and low income from wealthy areas were vulnerable during the pandemic. This result emphasizes the need to target resources and support for this subgroup during such crises.

Minimum inhibitory concentrations of antifungals against invasive isolates of Cryptococcus species worldwide: Global antifungal antimicrobial testing leadership and surveillance program, 2010-2020.

This study examined the geographic distribution of minimum inhibitory concentrations (MICs) of antifungals against Cryptococcus isolates. Data were collected on the MICs of specific antifungals (amphotericin B, 5-flucytosine, fluconazole, voriconazole, posaconazole, and isavuconazole) against various Cryptococcus species for the period 2010 to 2020 from the Antimicrobial Testing Leadership and Surveillance database. Cryptococcus isolates were collected from samples of blood and cerebrospinal fluid (CSF) from patients hospitalized in different regions worldwide. We applied the epidemiological cutoff values (ECVs) of antifungals against various Cryptococcus species to distinguish wild-type (WT) from non-WT Cryptococcus isolates. A total of 395 isolates of Cryptococcus species cultured from blood (n = 201) or CSF (n = 194) were analyzed. C. grubii (n = 270), C. neoformans (n = 111), and C. gattii (n = 11) were the three predominant species causing bloodstream infections (BSI) or meningitis/meningoencephalitis (MME). The proportion of MICs above the ECV (1 mg/L) for amphotericin B among C. neoformans isolates was significantly lower than that among C. gattii isolates (MICs >0.5 mg/L; P < 0.001), as evaluated using the chi-square test. For most isolates of the three predominant Cryptococcus species, the MICs of new triazoles were ≤0.25 mg/L. The MICs of fluconazole and amphotericin B in the BSI/MME-causing Cryptococcus isolates collected from patients hospitalized in the Asia-Western Pacific region and Europe were significantly lower (i.e., the distributions were more leftward) than those in North America and Latin America. Ongoing monitoring of MIC data for important antifungals against cryptococcosis is crucial.

Haemolysin Ahh1 secreted from Aeromonas dhakensis activates the NLRP3 inflammasome in macrophages and mediates severe soft tissue infection.

Severe soft tissue infections caused by Aeromonas dhakensis, such as necrotizing fasciitis or cellulitis, are prevalent in southern Taiwan and around the world. However, the mechanism by which A. dhakensis causes tissue damage remains unclear. Here, we found that the haemolysin Ahh1, which is the major virulence factor of A. dhakensis, causes cellular damage and activates the NLR family pyrin domain containing 3 (NLRP3) inflammasome signalling pathway. Deletion of ahh1 significantly downregulated caspase-1, the proinflammatory cytokine interleukin 1ß (IL-1ß) and gasdermin D (GSDMD) and further decreased the damage caused by A. dhakensis in THP-1 cells. In addition, we found that knockdown of the NLRP3 inflammasome confers resistance to A. dhakensis infection in both THP-1 NLRP3-/- cells and C57BL/6 NLRP3-/- mice. In addition, we demonstrated that severe soft-tissue infections treated with antibiotics combined with a neutralizing antibody targeting IL-1ß significantly increased the survival rate and alleviated the degree of tissue damage in model mice compared control mice. These findings show that antibiotics combined with therapies targeting IL-1ß are potential strategies to treat severe tissue infections caused by toxin-producing bacteria.

Phage transcriptional regulator X (PtrX)-mediated augmentation of toxin production and virulence in Clostridioides difficile strain R20291.

Clostridioides difficile is a Gram-positive, anaerobic, and spore-forming bacterial member of the human gut microbiome. The primary virulence factors of C. difficile are toxin A and toxin B. These toxins damage the cell cytoskeleton and cause various diseases, from diarrhea to severe pseudomembranous colitis. Evidence suggests that bacteriophages can regulate the expression of the pathogenicity locus (PaLoc) genes of C. difficile. We previously demonstrated that the genome of the C. difficile RT027 strain NCKUH-21 contains a prophage-like DNA sequence, which was found to be markedly similar to that of the φCD38-2 phage. In the present study, we investigated the mechanisms underlying the φNCKUH-21-mediated regulation of the pathogenicity and the PaLoc genes expression in the lysogenized C. difficile strain R20291. The carriage of φNCKUH-21 in R20291 cells substantially enhanced toxin production, bacterial motility, biofilm formation, and spore germination in vitro. Subsequent mouse studies revealed that the lysogenized R20291 strain caused a more severe infection than the wild-type strain. We screened three φNCKUH-21 genes encoding DNA-binding proteins to check their effects on PaLoc genes expression. The overexpression of NCKUH-21_03890, annotated as a transcriptional regulator (phage transcriptional regulator X, PtrX), considerably enhanced toxin production, biofilm formation, and bacterial motility of R20291. Transcriptome analysis further confirmed that the overexpression of ptrX led to the upregulation of the expression of toxin genes, flagellar genes, and csrA. In the ptrX-overexpressing R20291 strain, PtrX influenced the expression of flagellar genes and the sigma factor gene sigD, possibly through an increased flagellar phase ON configuration ratio.

Ribotypes and antimicrobial susceptibility profiles of clinical Clostridioides difficile isolates: A multicenter, laboratory-based surveillance in Taiwan, 2019-2021.

BACKGROUND: The clinical burden of Clostridioides difficile infections (CDIs) remains substantial globally. This study aimed to investigate the ribotypes (RTs) and antimicrobial susceptibility of C. difficile isolates collected in Taiwan. METHODS: C. difficile isolates were prospectively collected from four medical centers in Taiwan from 2019 to 2021. In a reference laboratory, in vitro susceptibility to clindamycin, moxifloxacin, metronidazole, vancomycin, fidaxomicin, and rifaximin were tested, and ribotyping was conducted to determine their genetic diversity. RESULTS: A total of 568 C. difficile isolates were included. Metronidazole resistance was not observed, and the susceptibility rate of vancomycin was 99.5 %. Clindamycin showed poor activity against these isolates, with a resistance rate of 74.8 %. Fidaxomicin exhibited potent activity and 97.4 % of isolates were inhibited at 0.25 µg/mL. Rifaximin MIC90 increased from 0.015 µg/mL in 2019 to 0.03 µg/mL in 2020 and 2021. Of 40 RTs identified, two predominant RTs were RT 078/126 (78, 14 %) and 014/020 (76, 13 %). RT 017, traditional harboring truncated tcdA, accounted for 3 % (20 isolates) and there was no isolate belonging to RT 027. The proportions of RT 078 increased from 11.2 % in 2019 to 17.1 % in 2021, and the predominance of RT 078/126 was more evident in central Taiwan. CONCLUSIONS: Vancomycin, fidaxomicin, and metronidazole remain in vitro effective against clinical C. difficile isolates in Taiwan. The reservoirs and genetic relatedness of two major RTs with zoonotic potentials, RT 078/126 and 014/020, warrant further investigations.

Global trends in non-susceptibility rates of Streptococcus pneumoniae isolates to ceftriaxone: Data from the antimicrobial testing leadership and surveillance (ATLAS) programme, 2016-21.

To understand the global changes in non-susceptibility rates of Streptococcus pneumoniae to ceftriaxone, we conducted a study using the Antimicrobial Testing Leadership and Surveillance database. A total of 15,717 S. pneumoniae isolates were collected from 2016 to 2021. The minimum inhibitory concentrations (MICs) were determined using broth microdilution. The overall susceptibility rates of S. pneumoniae isolates to penicillin, ceftriaxone and ceftaroline were 63.4%, 94.0% and 99.6%, respectively. The geometric mean of MICs and MIC50/MIC90 values of ceftriaxone were higher in Asia than in other continents. China (33.9%), South Korea (33.8%) and Taiwan (27.6%) had the highest ceftriaxone non-susceptibility rates, followed by Turkey, India, Brazil, Malaysia, South Africa and Colombia, with rates between 10% and 20%. During the study period from 2020 to 2021, Asia had the highest MIC90 value (4 mg/L) for ceftriaxone in S. pneumoniae isolates, and the geometric mean of MICs increased from 0.25 mg/L in 2016-2017 to 0.39 mg/L in 2020-2021. Both Asia (from 83.4% to 75.1%) and Latin America (from 94.2% to 86.3%) showed a decreasing trend in ceftriaxone susceptibility rates from 2016 to 2021. In North America, Europe and Oceania, the susceptibility rate was higher than 95%, and there was no obvious change in the rate during the 6 y. Further analysis of the data from Asia revealed that individuals younger than 6 y of age had a lower susceptibility rate to ceftriaxone (71.6% vs. 81.7%, P < 0.05) than patients ≥6 y. The higher non-susceptibility rates of ceftriaxone in S. pneumoniae in Asia may lead to therapeutic challenges in community-acquired pneumonia.

Rituximab, but not other biologics, impairs humoral immunity in patients with rheumatoid arthritis-a study using CoVariant protein arrays.

Objectives: RA is an autoimmune disease characterized by chronic inflammation and joint destruction. Biologics are crucial to achieving treat-to-target goals in patients with RA. The global spread and continuous variation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) necessitate the monitoring of variant-specific humoral responses post-vaccination. The aim of this study was to investigate how different biologic treatments for vaccinated RA patients might affect their neutralizing antibodies against multiple SARS-CoV-2 variants. Methods: We recruited RA patients who had received three doses of conventional SARS-CoV-2 vaccines and were treated with various biologics, e.g. TNF inhibitor (etanercept), IL-6 inhibitor (tocilizumab), CTLA4-Ig (abatacept) or anti-CD20 (rituximab). Serum samples were used to profile the binding and neutralizing antibodies using our own SARS-CoV-2 variant (CoVariant) protein array, developed previously. Results: Compared with healthy controls, only RA therapy with rituximab showed a reduction in neutralizing antibodies capable of targeting spike proteins in SARS-CoV-2 wild-type and most variants. This reduction was not observed in binding antibodies against SARS-CoV-2 wild-type or its variants. Conclusion: After receiving three doses of SARS-CoV-2 vaccination, RA patients who underwent rituximab treatment generated sufficient antibodies but exhibited lower neutralizing activities against wild-type and multiple variants, including current Omicron. Other biological DMARDs, e.g. TNF inhibitor, IL-6 inhibitor and CTLA4-Ig, did not show obvious inhibition.

Shigellosis in Taiwan: An old enteric pathogen with changing epidemiology and increasing antimicrobial resistance.

While the incidence of shigellosis has decreased in developed nations due to improved living conditions and healthcare systems, it remains prevalent in economically developing regions. In recent years, a resurgence of shigellosis has been observed in the United States, Europe, and Taiwan, primarily among men having sex with men and people living with human immunodeficiency virus, along with a rise in antimicrobial resistance. This study aims to review the historical epidemiological trends and drug resistance in shigellosis, with a focus on Taiwan. A comprehensive search was conducted using various databases and sources, including non-English literature in Japanese and Chinese. In developed countries, Shigella sonnei and Shigella flexneri are the most common species, while Shigella dysenteriae infections are sporadic. In Taiwan, the classification and prevalence of Shigella species have evolved over time, with S. flexneri and S. sonnei being the predominant strains. Fluoroquinolone resistance and azithromycin non-susceptibility are the ongoing threat. In conclusion, shigellosis remains a significant global health concern, with recent increases in certain populations and antimicrobial resistance. Further research is necessary to understand the clinical significance and risk factors associated with asymptomatic carriers and to assess the impact of behavioral modifications and interventions in high-risk populations.

Setting up a specialized maternity unit in a tertiary hospital: An oasis for pregnant women with COVID-19 during the pandemic.

OBJECTIVE: The COVID-19 pandemic has had an enormous impact on society and the medical environment in Taiwan in 2022. As pregnant women with COVID-19 are at higher risk for multiple complications, Taiwan needs a COVID-19 specialized maternity unit to improve the quality of maternal and neonatal care. MATERIALS AND METHODS: We share our experience with specialized maternity unit for pregnant women with COVID-19 at the National Cheng Kung University Hospital, where we can have careful evaluation, safe birth, and comprehensive postpartum care. RESULTS: Our COVID-19 specialized maternity unit enrolled 253 pregnant women with COVID-19, 90 (35.6%) pregnant women were admitted to the specialized maternity unit, and 71 (28.1%) pregnant women gave birth during hospitalization in two months. All pregnant women recovery well and real-time polymerase chain reaction tests on all infants were negative for COVID-19. CONCLUSION: A specialized maternity unit can provide pregnant women with a safe birth environment, immediate maternity care, and high medical quality. It can also help health workers in non-specialized maternity units deal with COVID-19-related psychological stress. Therefore, setting up one specialized maternity unit in the city during the pandemic should be guardedly considered.

Clinical impact of the combination of rapid species identification and antifungal stewardship intervention in adults with candidemia.

BACKGROUND: Candidemia is associated with a high mortality rate. This study aimed to evaluate the clinical impact of a diagnostic intervention and antifungal stewardship in adults with candidemia, including effectiveness in facilitating appropriate antifungals and improving patient outcomes. METHODS: A pre-post quasi-experimental study was conducted to analyze the impact of the integrated workflow of rapid species identification and antifungal stewardship intervention provided by infectious disease specialists for adults with candidemia at a medical center in southern Taiwan from March 1st, 2014 to February 29th, 2016. The primary endpoint was 30-day crude mortality, and secondary outcomes included the time to species identification, time to initial antifungal modification, and length of hospital stay. RESULTS: Total 303 patients with candidemia were included, including 152 adults in the pre-intervention period (Mar. 1st, 2014-Feb. 28th, 2015; control group) and 151 in the intervention period (Mar. 1st, 2015-Feb. 29th, 2016; case group). Demographic and clinical characteristics of patients in two groups were similar. The case group had a shorter time to species identification (72 vs. 96 h, P < 0.001) and earlier receipt of antifungals (47 vs. 59 h, P < 0.001) than the control group. Of note, the 30-day mortality rate (27.2% vs. 39.5%, P = 0.028) was lower and the hospital stay (43.5 vs. 46.0 days, P = 0.006) was shorter in the case group. CONCLUSION: Rapid diagnostic workflow and antifungal stewardship provided by infectious disease specialists can promote early initiation of antifungal therapy and improve outcome for adults with candidemia.

Predictive models for short-term mortality and length of hospital stay among adults with community-onset bacteraemia before and during the COVID-19 pandemic: application of early data dynamics.

BACKGROUND: The development of scoring systems to predict the short-term mortality and the length of hospital stay (LOS) in patients with bacteraemia is essential to improve the quality of care and reduce the occupancy variance in the hospital bed. METHODS: Adults hospitalised with community-onset bacteraemia in the coronavirus disease 2019 (COVID-19) and pre-COVID-19 eras were captured as the validation and derivation cohorts in the multicentre study, respectively. Model I incorporated all variables available on day 0, Model II incorporated all variables available on day 3, and Models III, IV, and V incorporated the variables that changed from day 0 to day 3. This study adopted the statistical and machine learning (ML) methods to jointly determine the prediction performance of these models in two study cohorts. RESULTS: A total of 3,639 (81.4%) and 834 (18.6%) patients were included in the derivation and validation cohorts, respectively. Model IV achieved the best performance in predicting 30-day mortality in both cohorts. The most frequently identified variables incorporated into Model IV were deteriorated consciousness from day 0 to day 3 and deteriorated respiration from day 0 to day 3. Model V achieved the best performance in predicting LOS in both cohorts. The most frequently identified variables in Model V were deteriorated consciousness from day 0 to day 3, a body temperature ≤ 36.0 °C or ≥ 39.0 °C on day 3, and a diagnosis of complicated bacteraemia. CONCLUSIONS: For hospitalised adults with community-onset bacteraemia, clinical variables that dynamically changed from day 0 to day 3 were crucial in predicting the short-term mortality and LOS.

Age and prior vaccination determine the antibody level in children with primary SARS-CoV-2 Omicron infection.

BACKGROUND: Protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection relies on immunity generated after primary infection. However, humoral immunity following primary infection with the Omicron variant is not well understood. METHODS: We prospectively recruited children <19 years with virologically-confirmed SARS-CoV-2 infection at National Cheng Kung University Hospital from February 2022 to September 2022 during the first wave of Omicron BA.2 outbreak in Taiwan. Serum samples were collected one month after acute infection to measure anti-spike protein receptor binding domain antibody levels and surrogate virus neutralizing antibody (NAb) levels against wild type disease and variants. RESULTS: Of the 164 patients enrolled, most were under 5 years (65.2%) with a diagnosis of upper respiratory tract infection. Children under 6 months with maternal coronavirus disease 2019 (COVID-19) vaccination had higher levels of both anti-SARS-CoV-2 spike antibody (119.0 vs 27.4 U/ml, p < 0.05) and anti-wild type NAb (56.9% vs 27.6% inhibition, p = 0.001) than those without. Children aged 5-12 years with prior vaccination had higher anti-spike antibody, anti-wild type, and anti-Omicron BA.2 NAb levels than those without (all p < 0.05). In previously naïve children without maternal or self-vaccination, those 6 months to 2 years had the highest antibody levels. Multivariable linear regression analysis showed age was the only independent factor associated with antibody level. CONCLUSIONS: In our study, children aged 6 months to 2 years have the highest antibody responses to SARS-CoV-2 Omicron variant infection. Age and prior vaccination are the main factors influencing the immunogenicity of SARS-CoV-2 infection.