Nasopharyngeal Swabs Research Articles

Impact of the 10-valent pneumococcal conjugate vaccine (PCV10) on pneumococcal carriage in healthy children and children with acute otitis media and pneumonia: emergence of serotypes 3, 6C and 19A in Croatia.

In 2019, the 10-valent pneumococcal conjugate vaccine (PCV10) was introduced in the Croatian immunization programme, a first for this European PCV-naïve country. This study aimed to evaluate the impact of PCV10 on pneumococcal serotype distribution among asymptomatic children and children with pneumonia and/or acute otitis media. Cross-sectional studies were conducted before and after the PCV10 introduction, with nasopharyngeal swabs collected from 1500 healthy children under 48months of age. An additional 324 children under 18years with pneumonia and/or acute otitis media, from whom Streptococcus pneumoniae was isolated, were also included. Isolates were identified by conventional methods, serotyped by Quellung reaction, and tested for antimicrobial susceptibility using disk diffusion and gradient test methods. We report prevalence, absolute risk (prevalence) difference (RD) and relative risk (prevalence) ratio (RR) differences between exposed and control children. Carriage prevalence among healthy children increased from 19.9% to 28.7%, primarily due to a rise in non-vaccine serotypes (NVT). Adjusted probabilities for serotypes 6C (RR 3.18; 95% CI, 1.43-7.06), 11A (RR 2.8; 95% CI, 1.22-6.39), 19A (RR 4.18; 95% CI, 1.18-14.9) and 23A (RR 3.93; 95% CI, 1.87-8.24) were significantly higher in healthy exposed children. Prevalences of these serotypes were also higher in exposed children with pneumonia/acute otitis media. In this cohort, serotype 3 increased (RR 4.6; 95% CI, 2.02-10.3), becoming the leading post-PCV10 isolate in the overall studied population. Serotypes 3 and 19A were almost entirely responsible for complicated pneumonia cases for which the probability increased by 21-fold. Antimicrobial susceptibility remained similar across periods. In the early post-vaccine period significant increase of PCV10 vaccine-related serotypes (6C, 19A) was observed. Continued monitoring is also essential due to concerning rise of serotype 3 in patients with mucosal infections and a higher risk for complicated pneumonia.

Over-the-counter carrageenan-based sprays may interfere with PCR testing of nasopharyngeal swabs to detect SARS-CoV-2.

Carrageenan-containing nasal sprays, available over-the-counter (OTC), are often marketed as having anti-viral effects. Carrageenan belongs to the glycosaminoglycan family alongside heparin, and heparin is known to inhibit real-time quantitative polymerase chain reaction (RT-qPCR) in nasopharyngeal swabs used to detect SARS-CoV-2. As heparin and carrageenan share structural similarities, this work aimed to investigate the interferent effect of carrageenan on RT-qPCR for SARS-CoV-2 detection across 4 different diagnostic platforms. This work demonstrated that in the presence of carrageenan samples return inaccurate and invalid results on the Seegene STARlet, while qualitative accuracy was maintained on the Cepheid GeneXpert, Roche Cobas LIAT, and Hologic Panther Aptima. Evidence of carrageenan interference on SARS-CoV-2 testing was consistent across two OTC brands and research-grade reconstituted iota-carrageenan, with 80% of results returning invalid regardless of the carrageenan formulation added to the samples. Further, a preliminary in vivo interference study demonstrated an increased Ct value within 15 minutes of carrageenan dosage, with Ct values restored 60 minutes post-application. A direct comparison of carrageenan- and heparin-mediated PCR interference demonstrated that carrageenan PCR interference occurs to a lesser degree, but is not reversible by the addition of heparinase I. As carrageenan is available OTC, interference with PCR testing that causes an increase in false negative results could lead to accidental spread of disease and could therefore have significant public health impacts on community testing of respiratory infectious diseases via PCR.

Validated HPLC method for simultaneous determination of azelastine hydrochloride fluticasone propionate and oxymetazoline in nasal mucosa and nasopharyngeal swabs from real human samples

A combination of three co-administrated drugs, such as azelastine hydrochloride (AZT), fluticasone propionate (FP), and oxymetazoline (OXY), is more effective than single therapy for the treatment of seasonal allergy and COVID-19. We established an efficient methodology for the determination of those analytes in spiked nasal mucosa and nasopharyngeal swabs from real human samples. A simple and quick protein precipitation method was used for sample extraction, using acetonitrile. RP-HPLC/DAD method was performed using an Exsil 100 ODS C18 (250 × 4.6 mm, 5 μm) column with an acetonitrile: water (70:30 v/v) solvent system at a flow rate of 0.7 mL/min. A photodiode array detector was applied at 240 nm. A good separation of the three proposed analytes with a short run time of 10 min was noted. Our method was validated according to FDA guidelines for bioanalytical validation methods. Calibration curves were linear in nasal mucosa samples at concentration ranges of 8–125, 10–100, and 10–125 µg/mL, with average recoveries ± SD of 101.56%±0.39, 102.45%±0.86, and 104.61%±4.52 for AZT, FP, and OXY; respectively. The results of precision and accuracy are within acceptable limits. According to stability assays, the three analytes under investigation were stable throughout sample preparation, storage, and injection. Our method was applied to real nasopharyngeal swabs. It shows that the results of the swabs were not affected by gender or age. Good recoveries with low % RSD were observed: 99.03% ± 0.75, 100.02% ± 0.94, and 100.94% ± 1.98 for both genders, and 100.45% ± 0.96, 100.69% ± 1.08, and 100.32% ± 1.53 for different ages for AZT, FP, and OXY; respectively. Moreover, the amount of those drugs in the nasal mucosa was observed for seven hours, and a constant concentration with a low% RSD was noted for the first four hours. Therefore, this method can be applied to monitor the therapeutic dose in the nasal mucosa for the determination of those analytes.

Validity of the Rapid Nasopharyngeal Antigen Swab for the Detection of SARS-CoV-2 on Cadavers

Background: SARS-CoV-2 is classified as a class 3 biological agent; therefore, autopsies on positive subjects must be performed in BSL 3 sectorial rooms. However, many centers lacking such facilities perform molecular nasopharyngeal swabs for SARS-CoV-2 on corpses before autopsy. This approach, though, is marked by prolonged reporting times and extremely high costs. This study aims to compare the results of molecular swabs (RT-PCR) with rapid antigen swabs (RAT) in order to assess if RAT can serve as the sole test for determining corpse positivity or negativity. Methods: Sixty corpses with positive molecular nasopharyngeal swabs for SARS-CoV-2, performed either ante-mortem or post-mortem, were selected. Afterward, they underwent rapid antigen swabs within 0 to 11 days after the last molecular exam. Results: Out of 60 corpses with positive molecular swabs, 52 antigen swabs were positive (86.67%), and 8 were negative (13.33%), indicating a sensitivity of 86.66% and specificity of 100%. Conclusions: Considering the sensitivity and specificity values observed in this study, RAT could be used as the primary investigation on corpses, especially in centers that lack BSL 3 sectorial rooms. Molecular swabs could then serve as a secondary test for subjects negative on RAT.

Isolation, genetic, and biological characterization of human adenovirus type 55 positive isolates from Wuhan, China.

Human adenovirus (HAdV) infection causes acute respiratory diseases in immunocompetent individuals worldwide. Infections by HAdV-55, one of the important pathogens leading to respiratory tract infections, often develop into pneumonia and are frequently associated with outbreaks in military camps and schools. We studied 186 HAdV-55-positive nasopharyngeal swab samples that were collected from patients with respiratory infection in Wuhan, China, from 2018 to 2019. Fifteen samples with high viral loads were selected for viral isolation and cultured with MRC-5 cells. These strains were then whole-genome sequenced to investigate their genetic characteristics by phylogenetic analyses. We then selected three HAdV-55 strains to quantify viral replication and further assessed the pathogenic characteristics of one strain in Syrian hamsters and BALB/c nude mice. HAdV-55-174 exhibited the highest replication ability in cultured cells compared to other strains, so this strain was selected for further investigation. Although the hamsters and mice were not so susceptible to HAdV-55-174 infection, viral loads were detected in the lungs and tracheas of the animal models, and persistent HAdV-55-174 replication was only observed in BALB/c nude mice. Histopathological lesions, including a widened alveolar septum and inflammatory cell infiltration, were observed in the lungs and tracheas of HAdV-55-174 infected animals. We isolated and characterized the HAdV-55 strains circulating in Wuhan from 2018 to 2019, which may be meaningful for further studies on HAdV-55 infection and pathogenesis.

Epidemiology and Genetic Evolutionary Analysis of Influenza Virus Among Children in Hainan Island, China, 2021–2023

Abstract: Background: During the COVID-19 pandemic, we continuously monitored the epidemiology of influenza virus among pediatric patients from January 2021 to December 2023 in Hainan Island, China. Methods: In this study, we collected 54,974 nasopharyngeal swab samples for influenza A Virus (IAV) testing and 53,151 samples for influenza B Virus (IBV) testing from pediatric outpatients. Additionally, we also collected 19,687 nasopharyngeal swab samples from pediatric inpatients for IAV and IBV testing. Outpatient samples were screened for influenza viruses (IVs) infection by the colloidal gold method. Targeted Next-Generation Sequencing (tNGS) was used to detect influenza virus infections in inpatients. Influenza virus types were identified by analyzing the HA/NA partial regions. Results: The findings revealed a significant decrease in the infection rate of IBV over the specified period, while the infection rate of IAV exhibited a rising trend. Additionally, B/Victoria lineage was the dominant epidemic strain in 2021, while the epidemic strains in 2022 and 2023 underwent a dynamic transformation from A/H3N2 to A/H1N1. Phylogenetic analysis revealed close relationships among the circulating strains. Nonetheless, because the sample size is limited, additional research is required. Conclusions: Our findings suggest that the predominant types of influenza viruses in the pediatric population are undergoing dynamic changes, influenced by the implementation and relaxation of non-pharmaceutical intervention measures. These findings highlight the need for adaptive influenza vaccination and containment strategies, particularly in tropical regions like Hainan, where climate and public health policies significantly impact viral transmission patterns. The insights gained from this study could inform more effective public health strategies in similar regions to mitigate the impact of influenza outbreaks in the future.

Nasopharyngeal carriage of Streptococcus pneumoniae among children and their household members in southern Mozambique five years after PCV10 introduction.

Streptococcus pneumoniae is an important cause of pneumonia, sepsis, and meningitis, which are leading causes of child mortality. Pneumococcal conjugate vaccines (PCVs) protect against disease and nasopharyngeal colonization with vaccine serotypes, reducing transmission to and among unvaccinated individuals. Mozambique introduced 10-valent PCV (PCV10) in 2013. In 2017-2019, 13-valent PCV (PCV13) replaced PCV10, and in September 2019 the schedule changed from three primary doses to two primary doses and a booster; the booster-containing schedule may increase indirect effects. We examined pneumococcal carriage in Mozambique to establish a baseline for estimating the impact of policy changes and to estimate the long-term impact of PCV10 in children aged <5years. We calculated prevalence of carriage of PCV10 serotypes and the 3 additional PCV13 serotypes ('PCV13-unique') among children aged <5years and their household members in southern Mozambique, between October 2018 and July 2019. Nasopharyngeal swabs were cultured, and isolates underwent Quellung serotyping. For children, we compared these "long-term post-PCV10" data with prior surveys ("pre-PCV" (2012-2013) and "post-PCV10" (2015-2016)) that used the same methods. In 2018-2019, among 1319 children aged under five years, 1064 (80.7%) were colonized with pneumococcus, among 614 children aged 5-<18years, 355 (57.8%) were colonized, and among 804 adults (aged ≥18years), 285 (35.4%) were colonized. The most frequently observed serotypes were 19A (n=154, 8.5% of isolates) and 6A (n=107, 5.9%), both PCV13-unique serotypes. Overall carriage prevalence among children under five years remained stable at approximately 80% across the carriage studies conducted between 2012 and 2019; between 2015 and 2016 and 2018-2019, the prevalence of PCV10-type carriage declined from 17.7% to 10.1%. Despite substantial declines in PCV10-type carriage initially following vaccine introduction, the continued circulation of PCV10 serotypes and relative high prevalence of PCV13-unique serotypes underscore the need to understand the impact of policy changes on pneumococcus transmission.

Variants and vaccines impact nasal immunity over three waves of SARS-CoV-2.

Viral variant and host vaccination status impact infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), yet how these factors shift cellular responses in the human nasal mucosa remains uncharacterized. We performed single-cell RNA sequencing (scRNA-seq) on nasopharyngeal swabs from vaccinated and unvaccinated adults with acute Delta and Omicron SARS-CoV-2 infections and integrated with data from acute infections with ancestral SARS-CoV-2. Patients with Delta and Omicron exhibited greater similarity in nasal cell composition driven by myeloid, T cell and SARS-CoV-2hi cell subsets, which was distinct from that of ancestral cases. Delta-infected samples had a marked increase in viral RNA, and a subset of PER2+EGR1+GDF15+ epithelial cells was enriched in SARS-CoV-2 RNA+ cells in all variants. Prior vaccination was associated with increased frequency and activation of nasal macrophages. Expression of interferon-stimulated genes negatively correlated with coronavirus disease 2019 (COVID-19) severity in patients with ancestral and Delta but not Omicron variants. Our study defines nasal cell responses and signatures of disease severity across SARS-CoV-2 variants and vaccination.

Severe acute respiratory syndrome coronavirus 2 variants in patients with coronavirus disease 2019 and environmental sampling from the hospital and market during the coronavirus disease 2019 pandemic in Thailand

Limited genomic surveillance data is available for SARS-CoV-2 in Thailand during the second and third wave outbreaks, including both patient and environmental samples. This study investigated the presence of SARS-CoV-2 RNA in patient samples, on frequently touched surfaces, and in environmental swab samples (EVSs) collected from urban markets in Bangkok between April 2021 and August 2022. A total of 78,159 nasopharyngeal swab samples from patients and 327 environmental swab samples from hospital and market settings were collected. SARS-CoV-2 RNA was detected in 3,706 of 78,159 patient samples and one of 327 environmental samples using real-time RT-PCR. In total, 54 patient samples and an environmental sample were subjected to whole-genome sequencing and mass array genotyping, respectively. Only 46 samples passed the quality assessment based on the analysis criteria. The lineages detected included B.1.1.529 (2 samples), B.1.1.7 (15 samples), B.1.351 (3 samples), B.1.36.16 (6 samples), B.1.617.2 (1 sample), AY.102 (1 sample), AY.4 (11 samples), AY.25 (1 sample), BA.1 (1 sample), BA.1.1 (3 samples), and BA.2 (2 samples). The phylogenetic analysis of the viral genome sequences revealed similar lineages during this study period.

Granuloma and persistent detection of wild-type rubella virus in an immunocompromised patient.

We report a case of wild-type rubella virus (genotype 2B) granuloma in a 29-year-old immunocompromised patient with a full vaccination scheme. He had been followed since his early teens for an unlabeled systemic inflammatory disease. On an inguinal node biopsy, histological analysis revealed a nguudiffuse non-necrotic granulomatous inflammation with no identified conventional infectious agent involved in granuloma formation. Further virological investigation revealed rubella virus (RuV) RNA detected by reverse transcription polymerase chain reaction (RT-PCR). Wild-type viral RNA persistence was documented in plasma samples collected up to 25 months after initial detection and also in different sequential biological samples (cerebrospinal fluid and nasopharyngeal swab). In the context of incomplete rubella eradication, RuV must be added to the list of potential triggers of chronic granuloma in immunodeficient patients.IMPORTANCERubella has become rare but has not yet disappeared. Rubella virus (RuV) must be added to the list of potential triggers of granuloma, particularly in immunodeficient patients. Diagnosis of RuV granulomas requires molecular testing of biopsy. RuV sequencing distinguishes between wild-type and vaccine-derived viruses and enables epidemiological surveillance.

Safety and efficacy of oral administrated cepharanthine in non-hospitalized, asymptomatic or mild COVID-19 patients: a Double-blind, randomized, placebo-controlled trial

Cepharanthine (CEP) is a natural remedy that potently inhibits SARS-CoV-2 activity both in vitro and in vivo. To evaluate the efficacy and safety of CEP compared with placebo in adults with asymptomatic or mild coronavirus disease 2019 (COVID-19), we conducted a proof-of-concept, double-blind, randomized, placebo-controlled trial. Patients were randomized to receive 120 mg/day of CEP, 60 mg/day CEP or placebo for 5 days. Main outcome was the time from randomization to negative nasopharyngeal swab and safety. Among 262 randomized participants, 188 completed the trial among group of 120 mg/day CEP (n = 65), 60 mg/day CEP (n = 68) and placebo (n = 55). Neither 120 mg/day or 60 mg/day CEP shortened the time to negative significantly compared with placebo. However, 60 mg/day CEP showed a slight trend (difference=-0.77 days, hazard ratio (HR) = 1.40, 95% CI 0.97–2.01, p = 0.072). In analysis of participants with good medication compliance, 60 mg/day CEP significantly shortened the time to negative (difference=-0.87 days, HR = 1.56, 95% CI 1.03–2.37, p = 0.035). Adverse events were not different among the three groups, and no serious adverse events occurred. In conclusion, treatment of asymptomatic or mild Covid-19 with 120 mg/day or 60 mg/day did not shorten the time to negative significantly. However, 60 mg/day CEP showed a slight trend which needs future confirmatory trials to validate. (NCT05398705).

Comparing sputum, nasopharyngeal swabs, and combined samples for respiratory bacterial detection using multiplex PCR.

This study offers important insights into refining diagnostic strategies for respiratory bacterial infections using multiplex PCR. This study finds that combining sputum and nasopharyngeal swabs into a single tube could serve as an effective alternative for detecting respiratory bacteria in adults with acute respiratory illness.

Ensitrelvir treatment-emergent amino acid substitutions in SARS-CoV-2 3CLpro detected in the SCORPIO-SR phase 3 trial.

The impact of treatment-emergent amino acid substitutions (TEAASs) in SARS-CoV-2 3C-like protease (3CLpro) on clinical and virologic outcomes was evaluated in patients with mild-to-moderate COVID-19 who received ensitrelvir 125 mg in the SCORPIO-SR trial. Individuals were randomised to ensitrelvir or matched placebo once daily for 5 days (first dose <72 h after disease onset). 3CLpro-TEAASs were identified by sequencing nsp5 encoding 3CLpro from pre- and post-treatment nasopharyngeal swabs. Time to resolution of a composite of five characteristic COVID-19 symptoms (TTR) was compared between patients with and without most common 3CLpro-TEAASs in the ensitrelvir arm. The ensitrelvir and placebo intention-to-treat populations comprised 345 and 341 patients, respectively. 3CLpro-TEAASs were detected in 19/204 (9.3%) ensitrelvir-treated and 3/137 (2.2%) placebo-treated patients with paired sequence data. The most common 3CLpro-TEAASs in the ensitrelvir arm were M49L (n=12), M49I (n=3) and S144A (n=2). In the placebo arm, all 3CLpro-TEAASs occurred in ≤1 patient. Median (95% confidence interval) TTR was comparable between patients with and without those TEAASs (158.8 h [112.1-281.9] vs 189.7 h [151.4-234.4]). Mean viral RNA levels declined more slowly in patients with M49L/I or S144A versus those without. Reductions in viral titre were unaffected by these TEAASs. The characteristics of recombinant SARS-CoV-2 with 3CLpro mutations were explored in vitro. Recombinant viruses with some 3CLpro mutations had reduced susceptibility to ensitrelvir in vitro, with limited effects on viral and competitive fitness. Continued surveillance is warranted to monitor the spread of viruses with 3CLpro mutations.

P-2173. Evaluation of Self/Parent Collected Oral/Nasal Swabs for Respiratory Illness in Symptomatic Children

Abstract Background For children under the age of 4 who are unable to reliably gargle, a combined oral/nasal (ON) swab collected by the parent/caregiver may be offered, and is less invasive than the standard nasopharyngeal (NP) swab. We sought to determine the diagnostic yield and acceptability of self-collected ON swab samples compared to healthcare worker-collected NP swabs for respiratory viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza, and respiratory syncytial virus (RSV) in children. Methods Symptomatic participants (0-4 years old) were recruited from a pediatric Emergency Department (ED) where they were undergoing clinical testing with an NP swab. Participants provided an additional ON swab using written self-collection instructions. Caregivers were asked to rate acceptability of ON and NP swab collections on a 5-point Likert scale. Both samples were collected with minitip flocked swabs and were tested with the SARS-CoV-2/Influenza A+B/RSV GeneXpert® assay. A portion of matched samples were also tested with the BioFire® RP2.1 respiratory panel. Results A total of 121 matched sample pairs were tested with the GeneXpert assay and had similar detection for RSV (28 ON positive vs 26 NP positive), influenza A (17 ON positive vs 17 NP positive), and SARS-CoV-2 (8 ON positive vs 10 NP positive). Median Ct values were higher for matched ON positives vs NP positives (26.2 vs 23.9). 58 pairs were also tested using the RP2.1 assay and showed a similar yield for total respiratory viruses detected (63 positive ON swabs vs 62 positive NP swabs). With either sample positive set as the reference for calculation of sensitivity, the ON and NP swab sensitivities are as follows: RSV (80.0% ON vs 100.0% NP), influenza A (94.4% ON vs 94.4% NP), SARS-CoV-2 (100.0% ON and 92.9% NP), and all other virus targets (82.6% ON vs 82.6% NP). Caregivers rated higher acceptability for ON swabs than HCW-collected NP swabs (median acceptability 2 vs 4). Conclusion The performance of self-collected ON swabs was similar to HCW-collected NP swabs for the detection of a range of respiratory viruses across two commercial molecular assays. Given their significantly higher acceptability ratings, self-collected ON swabs should be considered as a potential less-invasive diagnostic option for children. Disclosures All Authors: No reported disclosures

P-681. Estimated Incidence of Respiratory Syncytial Virus (RSV)-related Hospitalizations for Acute Respiratory Infections (ARIs), including Community Acquired Pneumonia (CAP), in Adults in Germany

Abstract Background RSV is a leading cause of ARI, including CAP, in older adults, but available data are limited and often substantially underestimate incidence. Among adults, single nasopharyngeal (NP) swab testing misses about half of RSV infections compared to using multiple specimen types. We estimated RSV-related ARI hospitalization incidence from a prospective CAP study and adjusted for undiagnosed RSV infections due to use of NP swab testing only. Methods We conducted an active, population-based multicenter surveillance of adult CAP hospitalizations in Thuringia (Germany) between 2021–2023. Participant NP swabs were RSV-tested by multiplex nucleic acid amplification tests. To estimate unadjusted RSV-related CAP incidence, age-group specific proportions of RSV detection among tested patients were applied to all-cause CAP incidence. Adjustments for underdiagnosis due to single site sampling and exclusion of non-CAP ARI were based on previous findings from a large, prospective, multispecimen study assessing the impact of collecting multiple specimens (NP swab, saliva, paired serology, and sputum) among 3,669 adults hospitalized for ARI. Results Among 1,040 radiologically confirmed CAP adults enrolled, 38 tested positive for RSV based on NP swabs, for an overall positive proportion of 3.7% among adults aged ≥18 years. Positive proportion increased to 7.8% after adjusting for higher RSV detection with multispecimen sampling compared to NP swab sampling only. The adjusted annual RSV-related CAP hospitalization rates were 4.7 (95% CI 1.5, 11.2) and 109.1 (95% CI 89.6, 131.6) per 100,000 population in adults aged 18-59 and ≥60 years, respectively. As CAP comprises only 28% of RSV-related ARI, the adjusted annual incidence of RSV-related ARI was 18.4 (95% CI 11.0, 28.9) and 377.6 (95% CI 340.5, 417.7) per 100,000 population for adults 18-59 and ≥60 years, respectively (Table1). Incidence estimates in Period 2 were about 3 times higher than in Period 1. Conclusion Older adults in Germany face a high burden of RSV-related ARI hospitalizations, including CAP, underscoring the potential utility of RSV vaccination for this population. These results align with recent time-series incidence analysis from Germany (236–363/100,000 for adults ≥60 years). Disclosures Caihua Liang, MD, PhD, Pfizer: Stocks/Bonds (Private Company) Elizabeth Begier, MD, M.P.H., Pfizer Vaccines: Employee|Pfizer Vaccines: Stocks/Bonds (Private Company) Liz Wang, MD; MS Biostatistics, Pfizer: employee|Pfizer: Stocks/Bonds (Public Company) Claudia Schwarz, PhD, Pfizer Inc.: employee|Pfizer Inc.: Stocks/Bonds (Private Company) Lea Johanna Bayer, n/a, Pfizer Pharma: Employee Christof Von Eiff, n/a, Pfizer Pharma: I am working as Sen. Medical Direktor for Vaccines at Pfizer Pharma GmbH, Berlin, , Germany and in that position I also get stocks. Qing Liu, M.S., Pfizer Inc.: Stocks/Bonds (Public Company) Jo Southern, PhD, MSc, Pfizer: Employee|Pfizer: Stocks/Bonds (Private Company) Jeffrey T. Vietri, PhD, Pfizer Inc.: Employment|Pfizer Inc.: Stocks/Bonds (Public Company) Bradford D. Gessner, M.D., M.P.H., Pfizer: Employee|Pfizer: Stocks/Bonds (Public Company) Christian Theilacker, MD, DTM&amp;H, Pfizer Inc: I am a Pfizer Employee|Pfizer Inc: Stocks/Bonds (Public Company)

P-40. Impact of case and control selection on influenza vaccine effectiveness (VE) among adults aged 40 years and older hospitalized with acute respiratory illness (ARI) during 2022-2023 using a test negative design (TND): secondary analysis of the North America multi-specimen study

Abstract Background Case and control definitions may impact VE estimates in observational studies. Using a TND design, we evaluated how influenza vaccine effectiveness against ARI hospitalizations changed when 1) influenza cases were detected through nasopharyngeal swabs (NPS) only versus multiple specimens and 2) controls included or excluded other vaccine preventable diseases (VPD). Methods Adults aged ≥40 years hospitalized for ARI had NPS and saliva or sputum tested using Luminex RSV/influenza multiplex PCR assay. Influenza was defined as either positive by NPS alone or positive by saliva, sputum, or NPS. Controls were defined as either all persons who were influenza negative or those negative for influenza and positive for respiratory syncytial virus (RSV). Exposure was self-reported seasonal influenza vaccination, defined as receipt of vaccine after 1 July 2022 and prior to 14 days of ARI illness onset. VE was calculated as 1 - ratio of odds of influenza vaccination among cases over controls. Results Among 2,999 patients with NPS and ≥1 other specimen, influenza detection increased by 40%, 74% and 91% when sputum, saliva, or both were added to NPS results, respectively (Table 1). Among 2,954 (98.5%) patients with influenza vaccine data, and when controls were defined as any influenza-negative ARI hospitalization, VEs were -3.6% (95%CI -49.5–28.3) and -0.9% (95% CI -32.5–23.2), using cases identified by NPS versus any specimen type, respectively (Table 2). When controls were persons who were RSV positive and influenza negative, VEs were 38.5% (95% CI -3.5–63.4) and 43.2% (95% CI 14.9–62.1) using cases identified by NPS versus any specimen type, respectively. Conclusion Adding saliva and sputum nearly doubles influenza detection compared to NPS alone but does not substantially alter VE estimates. By contrast, VE was substantially increased when defining controls as those who were RSV+, yielding a result closer to the US Centers for Disease Control and Prevention values of 39-43% for the same season. The latter increase in VE may have occurred because RSV positivity reduces confounding caused by inclusion of other vaccine preventable infections (ie, SARS-CoV-2) in the control group due to correlation between vaccination against influenza and SARS-CoV-2. Disclosures Negar Aliabadi, MD, MS, Pfizer Inc: employment|Pfizer Inc: Stocks/Bonds (Public Company) Qing Liu, M.S., Pfizer Inc.: Stocks/Bonds (Public Company) Julio A. Ramirez, MD, FACP, Pfizer: Julio Ramirez is an employee of Norton Healthcare (Louisville, KY), which received fees from Pfizer in relation to this study. Allison McGeer, MD, AstraZeneca: Honoraria|GSK: Honoraria|Merck: Honoraria|Moderna: Honoraria|Novavax: Honoraria|Pfizer: Grant/Research Support|Pfizer: Honoraria|Roche: Honoraria|Seqirus: Grant/Research Support|Seqirus: Honoraria Ruth Carrico, PhD, DNP, APRN, Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Seqirus: Advisor/Consultant Samira Mubareka, MD, Pfizer: Grant/Research Support Verna Welch, PhD, MPH, Pfizer Inc.: Stocks/Bonds (Public Company) Malak Elsobky, MD, Pfizer: Stocks/Bonds (Public Company) Bradford D. Gessner, M.D., M.P.H., Pfizer: Employee|Pfizer: Stocks/Bonds (Public Company) Elizabeth Begier, MD, M.P.H., Pfizer Vaccines: Employee|Pfizer Vaccines: Stocks/Bonds (Private Company)

P-1003. Group B Streptococcus Colonization in Pregnant Women and Their Infants: Prevalence of Colonization, Vertical Transmission, and Serotype Dynamics

Abstract Background Group B Streptococcus (GBS) is a leading cause of neonatal mortality and morbidity worldwide. Despite historically lower colonization rates among pregnant Korean women compared to those in Western countries, recent studies indicate a rising trend in GBS colonization rates and serotype changes. This study aimed to investigate GBS colonization rates, vertical transmission, and serotype distribution among pregnant women and their infants in Korea. Methods A prospective, mother-infant paired cohort study was conducted from January 2020 to November 2023. Vaginal and rectal swabs were obtained from pregnant women, while gastric aspirate and nasopharyngeal swabs were collected from infants immediately after birth, and nasopharyngeal and rectal swabs were obtained at one and two months of age. Serotyping and multilocus sequence typing (MLST) of GBS isolates were performed. Results Among 427 pregnant women, 67 (15.7%) tested positive for GBS colonization. Serotype III (24%), followed by V (22.4%), VIII (19.0%), and Ib (17.2%), were the predominant serotypes, with the most common sequence types (ST) being ST2, ST19, and ST10. Vertical transmission was observed in one infant at birth, presenting with serotype V. GBS colonization was identified in four infants at one month of age, with serotypes Ia and VIII. Of these, serotype Ia persisted in two infants, while serotype III was newly detected in one infant at two months of age. Conclusion The increasing trend in GBS colonization among pregnant Korean women highlights the need for continuous monitoring. GBS colonization was observed in infants at birth and up to two months of age, emphasizing the importance of ongoing surveillance of GBS colonization rates and serotype distribution to establish guidelines and preventive strategies in Korea. Disclosures All Authors: No reported disclosures

P-2177. The Prevalence of Respiratory Viral Pathogen Detection on Nasopharyngeal Specimens Evaluated by Multiplex Polymerase Chain Reaction Among Asymptomatic Children

Abstract Background While current viral detection methods demonstrate high sensitivity, their clinical relevance remains inexact. We evaluated the prevalence of respiratory viral pathogen detection (RVPD) using multiplex polymerase chain reaction (M-PCR) and its correlation with nasal immune cell quantities and reported respiratory viral symptoms (RVS) in asymptomatic or pauci-symptomatic children. Demographic and Clinical Characteristics of 20 Children at Enrollment in the Pediatric Respiratory Co-infection and Immunologic Response Study (Peds RECON) Legend: ^= Nasopharyngeal specimens were processed using the BioFire® Respiratory 2.1 (RP2.1) Panel * = within 10 days of the participant’s enrollment visit + = Symptoms queried: fever, headache, runny or dripping nose, sore or painful throat, trouble breathing/shortness of breath, chest tightness/pain, dizziness, coughing, nausea, vomiting, diarrhea, clingy, fussy, decreased energy level #= Among 15 participants where blood sample was available; 4 of 7 participants with positive M-PCR and 11 of 13 participants with negative M-PCR NP=Nasopharyngeal; SD= Standard deviation; M- PCR= Multiplex Polymerase Chain Reaction Methods The ongoing Pediatric Respiratory Co-infection and Immunologic Response Study (Peds RECON) measures clinical and immune responses during respiratory viral infections in participants aged 1 month to 17 years, enrolled while healthy, with follow-up visits during illness over two years. Enrollment involves demographic data collection, a 10-day respiratory symptom review, and sample collection (nasopharyngeal (NP) swab and peripheral blood (PB)). NP swabs undergo M-PCR using the BioFire® Respiratory 2.1 panel, and both NP swabs and PB samples undergo immune cell quantification. A prevalence rate was calculated based on M-PCR-positive NP swabs per all collected NP swabs. A t-test compared NP immune cell counts between participants with and without RVPD at enrollment, while logistic regression assessed the association with RVS and RVPD. Participant Findings by Multiplex PCR Positivity in 20 Peds RECON Participants at Enrollment Legend: += positive -= Negative ^= Rhinovirus/Enterovirus and Parainfluenza 3 #=Number NS= not significant, p-value ≥ 0.05 Peds RECON- Pediatric Respiratory Co-infection and Immunologic Response Study NP= Nasopharyngeal (NP) M-PCR= Multiplex Polymerase Chain Reaction, Nasopharyngeal specimens were processed using the BioFire® Respiratory 2.1 (RP2.1) Panel PBMC=Peripheral Blood Mononuclear Cells Results From January to May 2024, 20 children (median age: 11 years) were enrolled (table). Most reported respiratory illness ≥4 weeks prior (n=16). Seven NP swabs tested positive among 20 NP swabs (35% prevalence rate), primarily rhinovirus/enterovirus. At enrollment, 45% reported at least one respiratory symptom in the preceding 10 days. The mean nasal immune cell count was 85,920 (SD: 74,872), with no significant association between RVPD and immune cell counts (t (18) =0.27, p=0.80) or RVS (OR: 0.88; 95% CI: 0.14; 5.58) (figure A; D). Conclusion Thirty-five percent of apparently healthy children in Peds RECON had a RVP detected on M-PCR, highlighting the discrepancy between clinical appearance and RVPD. Nasopharyngeal cell isolation did not correlate with positive M-PCR or reported symptoms, demonstrating M-PCR positivity for certain pathogens is indicative of asymptomatic presence of viral RNA. Further research is required to determine if asymptomatic shedding occurs or if the sensitivity of the assay for certain pathogens requires optimization. Disclosures All Authors: No reported disclosures

P-713. Two Seasons of Admissions Screening for Influenza and RSV Among a Highly Immunocompromised Patient Population

Abstract Background To facilitate early detection and prompt isolation of infected patients during the 2022-23 and 2023-24 fall/winter seasons, the NIH Clinical Center, a clinical research hospital serving a significantly immunocompromised patient population, augmented symptom screening with Influenza and RSV testing of all patients on admission. Methods Nasopharyngeal (NP) swabs were collected on admission from November 2022-April 2023 and September 2023-April 2024. All samples were tested for Influenza and RSV by PCR on the Panther Fusion® SARS-CoV-2/FluA/B/RSV Assay (Hologic, Inc.) or the Xpert® Xpress CoV-2/Flu/RSV test. Patients who disclosed symptoms on admission were tested using the BioFire® Respiratory Panel. Medical chart reviews and discussions with patient care providers elucidated whether cases identified on admission were asymptomatic. Results Of 3197 NP swabs collected from patients admitted to our hospital, 31 swabs were from patients who were symptomatic on admission. Of the remaining 3166 NP swabs (from 2352 unique patients, as some patients had multiple admissions), 17 patients were found to be infected: 7 (0.22%) Influenza A, 1 (0.03%) Influenza B, and 9 (0.28%) RSV. Of these patients that were asymptomatic on admission, 8 (47%) subsequently disclosed symptoms (1 with recent confirmed diagnosis of Rhinovirus/Enterovirus infection), 2 (12%) disclosed a recent history of an unknown respiratory infection, and 7 (41%) were asymptomatic. Seven Influenza A and 8 RSV infections were detected between the months of November and January, yielding positivity rates of 0.57% and 0.66%, respectively, during these months when community transmission was highest. Conclusion Admission surveillance for Influenza and RSV during months of increased community transmission allowed us to isolate seventeen patients on admission who would likely not have been appropriately isolated based on symptom screening alone. Admission surveillance testing, in conjunction with symptomatic surveillance, is important to identify infected patients promptly during increased respiratory virus activity in the community, and especially for institutions serving immunocompromised patients. Disclosures All Authors: No reported disclosures

P-1975. Detection of SARS-CoV-2 Specific Secretory IgA and Neutralizing Antibodies in Nasal Secretions of Seronegative Individuals Previously Exposed to COVID-19

Abstract Background Mucosal immunity may contribute to clearing SARS-CoV-2 infection prior to systemic infection. We describe detection of SARS-CoV-2 specific nasal mucosal antibodies in a group of exposed household individuals that evaded systemic infection and remained seronegative.Figure 1.SARS-CoV-2-specific nasal SIgA. SARS-CoV-2-specific nasal SIgA in control and exposed participants (A). Positive thresholds of 0.20 and 6.30 AU/mL were calculated for unadjusted and adjusted SIgA, respectively, based on mean + 3 standard deviation of the control samples. Exposed participants were stratified by the positive threshold and unadjusted (B) SIgA and adjusted (C) SIgA were compared to controls and infected participants. Wilcoxon rank-sum tests determined if medians differed significantly. Methods Between June 2020 and February 2023, nasopharyngeal swabs (NPS) samples and acute and convalescent blood were collected from individuals exposed to a SARS-CoV-2-confirmed household member. Nasal secretory IgA (SIgA) antibodies targeting the SARS-CoV-2 spike protein were measured using a modified ELISA.Figure 2.SARS-CoV-2-specific nasal unadjusted (A) and adjusted (B) SIgA levels at Day 1 (enrollment), Day 8, and Day 15 for exposed seronegative with positive nasal SIgA and infected participants. SARS-CoV-2-specific nasal unadjusted (A) and adjusted (B) SIgA levels at Day 1 (enrollment), Day 8, and Day 15 for exposed seronegative with positive nasal SIgA and infected participants. Wilcoxon signed-rank tests were used to determine if medians (gray) differed significantly. Results Of 36 exposed individuals without SARS-CoV-2 detected by RT-PCR of NPS specimens and seronegative for SARS-CoV-2-specific IgG at acute and convalescent visits, 13 (36.1%) had positive SARS-CoV-2-specific SIgA levels detected in the nasal mucosa. These individuals had significantly higher nasal SIgA (median 0.52 AU/mL) compared with never-exposed, never-infected controls (n=29, 0.001 AU/mL) and infected-family members (n=43, 0.0002 AU/mL) during the acute visit, respectively (both P&amp;lt; 0.001, Figure 1). The nasal SARS-CoV-2-specific SIgA decreased rapidly over two weeks in the exposed seronegative individuals (Day 1 [0.52 AU/mL] vs. Day 8 [0.18 AU/mL] vs. Day 15 [median 0.02 AU/mL], P = 0.001 and 0.13, respectively, Figure 2). In contrast, SIgA increased in infected family members (Day 1 [0.0002 AU/mL] vs. Day 8 [0.65 AU/mL] vs. Day 15 [median 1.14 AU/mL], P &amp;lt; 0.001 and P = 0.09, respectively, Figure 2). Conclusion Transient nasal SARS-CoV-2-specific SIgA detected in exposed, seronegative individuals may have a protective role in preventing systemic infection. Elucidating factors associated with the induction of nasal SIgA response that prevent systemic invasion may inform infection and transmission prevention strategies. Disclosures Pia S. Pannaraj, MD, MPH, AstraZeneca: Grant/Research Support|Pfizer: Grant/Research Support