Background Respiratory tract infections are a major cause of pediatric hospitalization. Post-COVID-19 pandemic, atypical surges and disrupted respiratory pathogen circulation underscore the need for continuous surveillance. Methods We retrospectively analyzed respiratory pathogen detection among hospitalized children aged 28 days to 18 years at the largest quaternary hospital in Malaysia from January 2018 to May 2023. The study period was classified into pre-pandemic (2018–2019), pandemic (2020–2021), and post-pandemic (2022–2023) phases. Respiratory pathogens were identified using the FilmArray BioFire® Respiratory Panel 2.1. Results Among 20,556 hospitalized children, 7707 (37.5%) underwent BioFire® testing. Overall pathogen positivity remained similar during the pre-pandemic and pandemic periods (50.4% and 50.9%, respectively) and increased to 86.2% post-pandemic. Single-pathogen infections increased from 46.4% to 43.1% to 64.6%, while co-infections rose from 4.0% to 7.9% to 21.6%, respectively. Human rhinovirus/enterovirus and respiratory syncytial virus were consistently detected, whereas adenovirus and influenza viruses increased significantly post-pandemic. Influenza A and B re-emerged after minimal detection during the pandemic, returning to pre-pandemic detection rates. Monthly positivity varied substantially before and during the pandemic but remained consistently high post-pandemic, peaking at 94.4%. Despite increased pathogen detection, pediatric intensive care unit admissions remained low across all periods. Conclusion Substantial post-pandemic increases in respiratory pathogen positivity, co-infections, and pathogen diversity were observed among hospitalized children despite stable pediatric intensive care unit admission rates. These findings likely reflect respiratory pathogen re-emergence following relaxation of non-pharmaceutical interventions, altered exposure patterns, and increased BioFire® testing after the COVID-19 pandemic.
N. Che-Kamaruddin, Siti Naqiah Hudari, Norziha Zainul Abidin et al.· new microbes and new infecti...· 0 citations
Introduction Understanding how different COVID-19 vaccine combinations shape long-term immunity is essential for improving durability and guiding booster strategies. Despite extensive characterization of neutralizing antibodies, long-term memory B and T cell responses after homologous and heterologous vaccination regimens remain poorly understood. Methods In this study, peripheral blood mononuclear cells (PBMCs) from 50 individuals were analyzed 12 months after completion of a homologous two-dose primary COVID-19 vaccination series and had received a single booster dose (12-month follow-up). Participants initially received BNT162b2, ChAdOx1 nCoV-19, or CoronaVac as the primary vaccination series, followed by either a homologous booster or a heterologous BNT162b2 booster (ChAdOx1 nCoV-19/BNT162b2 and CoronaVac/BNT162b2). Unvaccinated individuals served as controls. B cell phenotypes were assessed using flow cytometry, while B and T cell recall responses were determined using ELISpot. IgG levels and cytokine/chemokine/growth factor profiles were evaluated using ELISA and Bio-Plex multiplex before and after in vitro stimulation. Results The homologous BNT162b2 vaccination regimen exhibited significantly higher frequencies of memory B cells recognizing the ancestral (Wuhan strain-derived) SARS-CoV-2 Spike protein compared to the ChAdOx1 nCoV-19, CoronaVac, and unvaccinated controls. The CoronaVac/BNT162b2 vaccination regimen demonstrated significantly elevated RBD-specific IgG+ memory B cells and higher stimulated IgG levels, together with the highest IFN-γ-producing T cell responses. Homologous CoronaVac and CoronaVac/BNT162b2 vaccination regimens showed broader cytokine activation, including IL-6, IL-9, IL-15, TNF-α, and other cytokines. IL-6 levels were positively associated with memory B cell frequencies, suggesting a potential association with memory B cell differentiation and maintenance. Discussion Different vaccination regimens were associated with distinct long-term cellular immune profiles under real-world conditions, with both homologous BNT162b2 and heterologous CoronaVac/BNT162b2 vaccination regimens maintaining robust memory B cell signatures and functional recall responses. The results highlight how priming combinations shape the durability and quality of immune memory, supporting the potential utility of mixed-platform booster strategies for sustaining long-term immunity.
N. Che-Kamaruddin, J. Johari, Hasmawati Yahaya et al.· Frontiers in Immunology· 0 citations
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