ObjectiveMycoplasma pneumoniae (M. pneumoniae) is an important pathogen of community acquired pneumonia. With the outbreak of coronavirus disease 2019 (COVID-19), the prevalence of some infectious respiratory diseases has varied. Epidemiological features of M. pneumoniae in children from Beijing (China) before and during the COVID-19 pandemic were investigated.MethodsBetween June 2016 and May 2021, a total of 569,887 children with respiratory infections from Children’s Hospital Affiliated to Capital Institute of Pediatrics (Beijing, China) were included in this study. M. pneumoniae specific-IgM antibody in serum specimens of these patients was tested by a rapid immunochromatographic assay kit. The relevant clinical data of M. pneumoniae-positive cases were also collected, and analyzed by RStudio software.ResultsThe results showed that 13.08% of collected samples were positive for M. pneumoniae specific-IgM antibody. The highest annual positive rate was 17.59% in 2019, followed by 12.48% in 2018, 12.31% in 2017, and 11.73% in 2016, while the rate dropped to 8.9% in 2020 and 4.95% in 2021, with significant difference. Among the six years, the positive rates in summer and winter seasons were significantly higher than those in spring and autumn seasons (p < 0.001). The positive rate was the highest in school-age children (22.20%), and lowest in the infant group (8.76%, p < 0.001). The positive rate in boys (11.69%) was lower than that in girls (14.80%, p < 0.001). There were no significant differences in different seasons, age groups, or genders before and during the COVID-19 pandemic (p > 0.05).ConclusionsOur study demonstrated that an M. pneumoniae outbreak started from the summer of 2019 in Beijing. After the COVID-19 pandemic outbreak in the end of 2019, the M. pneumoniae positive rates dropped dramatically. This may be due to the restrictive measures of the COVID-19 pandemic, which effectively controlled the transmission of M. pneumoniae. The relationships between M. pneumoniae positive rates and season, age, and gender were not statistically significant before and during the COVID-19 pandemic.

ObjectiveTo analyze the positivity and levels of SARS-CoV-2 antibodies in vaccinated children to evaluate the humoral immune response of vaccination on pediatric population. Analysis on the causes of antibody positivity in unvaccinated children.MethodsA retrospective study was conducted on children who were admitted to the Children’s Hospital Affiliated to Capital Institute of Pediatrics. The clinical data of serological testing of SARS-CoV-2 immunoglobulin M (IgM) and IgG antibodies were collected from SARS-CoV-2 vaccinated or unvaccinated children with no evidence of prior novel coronavirus infection. Chemiluminescence immunoassay was utilized for the in vitro determination of SARS-CoV-2 antibodies.ResultsA total of 3,321 healthy children aged 6-11 years received two doses of inactivated SARS-CoV-2 vaccine. At 1 month after the second dose, the positive rate (96.5%) and levels [8.039 (interquartile range (IQR), 6.067-9.098)] of SARS-CoV-2 IgG antibodies reached the peak and remained at a high level for 2-3 months, after which the positive rate and level of vaccine-induced IgG antibody gradually decreased. Compared with 1 month after the second dose of vaccine, the positive rate of IgG antibody decreased to 70.4% at 7 months, and the antibody level decreased by 69.0%. A total of 945 children aged 3-5 years received one or two doses of inactivated vaccine. The positive rate and levels of SARS-CoV-2 IgG antibody in participants remained high for 3 months after vaccination. There was no gender-based difference in positive rate of IgG antibody in children aged 3-11 years old (P>0.05). Among the 5,309 unvaccinated children aged 0 day to 11 years, 105 (2.0%) were positive for SARS-CoV-2 IgG antibody, which was associated with passive infusion. The maternal humoral response to COVID-19 vaccination in noninfected pregnant women was transferred through the placenta to the fetus, and some children obtained SARS-CoV-2-positive antibodies through blood transfusion.ConclusionsInactivated SARS-CoV-2 vaccines could induce robust humoral immune response that gradually declined within several months after the second dose. Therefore, it helps to determine whether children receive a booster dose and elicit a long-term memory immune response. Positive SARS-CoV-2 antibodies in unvaccinated children were associated with passive IgG antibody infusion.

Complete blood count (CBC) is one of the routine blood tests used for clinical diagnosis, disease treatment, and health assessment. 1 Comparing test results with the appropriate reference intervals (RIs) is the first step in the clinical interpretation of these laboratory results. 2 However, there are no consensus-based CBC RIs for children, and many medical institutions still apply RIs determined from adults, from children in other countries, or from children in a different age range. 3 Due to racial and environmental differences, genetic variation, and hematological changes associated with growth and development, there may be great differences in CBC parameters between children from different countries and in different age stages. [2][3][4] Several scientists have noticed this problem and made great contributions to establishing CBC RIs for children.

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Background: Heparin-binding protein (HBP) is a promising candidate as a biomarker for sepsis. However, there is limited study on the use of HBP among children with sepsis in pediatric intensive care unit (PICU). The aim of this study is to assess HBP as a diagnostic and prognostic biomarker of severe sepsis in the PICU.Methods: A multicenter, prospective study was conducted among children with sepsis and severe sepsis in nine different PICUs in China from October 2019 to June 2021. Plasma levels of HBP, procalcitonin (PCT), C-reactive protein (CRP), lactate, and white blood cell (WBC) count were determined at enrollment and 72 hours after enrollment. Receiver operating characteristic curve (ROC) analysis was used to evaluate the ability of biomarkers in diagnosing severe sepsis. Multivariate logistical analysis was performed to assess the association between biomarkers and in-hospital mortality. Spearman's correlation was used to identify the relationship between HBP and other biomarkers.Results: Of 355 included patients, 132 patients were diagnosed with non-severe sepsis (referred to as sepsis), 223 patients had severe sepsis. Patients with severe sepsis had significantly elevated levels of HBP compared with sepsis (median 170.5 vs. 74.1 ng/mL, P<0.001). Adding HBP to a diagnostic model with PCT and lactate could significantly improve the diagnostic capability for severe sepsis (area under the curve (AUC) 0.702 vs. 0.628, p<0.001). The plasma levels of HBP correlated positively with the number of dysfunctional organs. After adjusting for confounding factors, the HBP levels at enrollment could not predict in-hospital mortality. However, declined levels of HBP at 72 hours had a significant association with decreased in-hospital mortality (adjusted odds ratio (aOR) 0.242, P<0.001). The levels of HBP showed weak positive correlations with PCT, CRP, WBC, and no correlation to lactate.Conclusions: HBP at enrollment can be an independent indicator for severe sepsis and the dynamic changes at 72 hours can be a predictor for in-hospital mortality in PICU.