Journal of Infection and Chemotherapy

[Objective]Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody titers level and duration of elevated levels are considered important indicators for confirming the efficacy of coronavirus disease 2019 (COVID-19) vaccines. The objective of this study was to demonstrate the changes in antibody titers after the second and third doses of the COVID-19 vaccine, and to determine the antibody titers in cases of spontaneous infection with SARS-CoV-2 after vaccination. [Materials and Met...

IntroductionAntigen testing is essential in the clinical management of COVID-19. However, most evaluations of antigen tests have been performed before the emergence of the Omicron variant. Thus, an assessment of the diagnostic performance of antigen tests for the detection of SARS-CoV-2 during the circulation of Omicron variant is required. MethodsThis prospective observational study evaluated QuickNavi-COVID19 Ag, a rapid antigen detection test between December 2021 and February 2022 in Japan,...

IntroductionRapid qualitative antigen testing has been widely used for the laboratory diagnosis of COVID-19 with nasopharyngeal samples. Saliva samples have been used as alternative samples, but the analytical performance of those samples for qualitative antigen testing has not been sufficiently evaluated. MethodsA prospective observational study evaluated the analytical performance of three In Vitro Diagnostics (IVD) approved COVID-19 rapid antigen detection kits for saliva between June 2022 a...

Japan has reported a small number of COVID-19 cases relative to other countries. Because not all infected people receive diagnostic tests for COVID-19, the reported number of COVID-19 cases must be lower than the actual number of infections. Assessments of the presence of antibodies against the spike protein of SARS-CoV-2 can retrospectively determine the history of natural infection and vaccination. In this study, we assessed SARS-CoV-2 seroprevalence by analyzing over 60,000 samples collected ...

We evaluated the rapid immunochromatographic test for SARS-CoV-2 antigen detection using 16 saliva specimens collected from 6 COVID-19 hospitalized patients, and detected N-antigen in 4 of 7 RT-PCR positive specimens. The POCT antigen test using saliva is highly considered to be a game-changer for COVID-19 diagnosis.

ObjectivesAntigen tests have recently emerged as an interesting alternative to SARS-CoV-2 diagnostic PCR, thought to be valuable especially for the screening of bigger communities. To check appropriateness of the antigen based testing, we determined sensitivity of two point-of-care antigen tests when applied to a cohort of COVID-19 symptomatic, COVID-19 asymptomatic and healthy persons. MethodsWe examined nasopharyngeal swabs with antigen test 1 (Panbio Covid-19 Ag Rapid Test, Abbott) and antig...

The novel coronavirus disease 2019 (COVID-19) pandemic has spread rapidly worldwide. To prevent the spread of COVID-19, mRNA-based vaccines made by Pfizer/BioNTech (BNT162b1) and Moderna (mRNA-1273) have been widely used worldwide, including in Japan. Various adverse events after COVID-19 mRNA vaccinations have been reported, with differences observed among individuals. However, the analysis on the genetic background for susceptibility to side effects has been limited. In the present work, we pe...

Rapid diagnosis of COVID-19 is essential for instituting measures to prevent viral spread. SARS-CoV-2 antigen rapid diagnostic test (Ag-RDT) based on lateral flow immunochromatography assay (LFIA) principle can visually indicate the presence of SARS-CoV-2 antigens as a band. Ag-RDT is clinically promising as a point-of-care testing because it can give results in a short time without the need for special equipment. Although various antigen capture LFIAs are now available for rapid diagnosis for S...

BackgroundLittle is known about the population prevalence of antibodies against emerging immune escape variants of SARS-CoV-2. MethodsA population-based prevalence study was conducted in Yokohama City, the most populous municipality of Japan. Quantitative measurements of immunoglobulin G against SARS-CoV-2 spike protein (SP-IgG) and qualitative measurements of neutralization antibodies against the Omicron BA.1 and BA.2 variants were performed. ResultsOf 6,000 randomly selected residents aged 2...

The rapid diagnosis of Campylobacter infections is important for the management of infectious gastroenteritis. Although stool culture is considered the gold standard, its sensitivity is limited and it requires prolonged incubation times. We performed a prospective multicenter study at nine healthcare facilities in Japan to evaluate a Campylobacter rapid antigen test using stool specimens between March 2024 and August 2025. Patients with suspected infectious gastroenteritis were consecutively enr...

The rise of mutant strains of SARS-CoV-2 poses an additional problem to the existing pandemic of COVID-19. There are rising concerns about the Mu variant which can escape humoral immunity acquired from infections from previous strains or vaccines. We examined the neutralizing efficacy of the BNT162b2 mRNA vaccine against the Mu variant and report that the vaccine has 76% neutralizing effectiveness against the Mu compared to 96% with the original strain. We also show that Mu, similar to the Delta...

The SARS-CoV-2 Omicron variant has become the dominant SARS-CoV-2 variant around the world and exhibits immune escape to current COVID-19 vaccines to some extent due to its numerous spike mutations. Here, we evaluated the immune responses to booster vaccination with intramuscular adenovirus-vectored vaccine (Ad5-nCoV), aerosolized Ad5-nCoV, a recombinant protein subunit vaccine (ZF2001) or homologous inactivated vaccine (CoronaVac) in those who received two doses of inactivated COVID-19 vaccines...

Identification and isolation of persons infected with SARS-COV-2 are key mitigation strategies in the current pandemic, and rapid antigen detection tests (RADTs) offer the promise of decreased turnaround time to diagnosis when compared with gold standard RT-PCR testing. We evaluated the analytical performance of the Abbott(R) Panbio RADT on nasopharyngeal samples stored at the Ministry of Health National Reference Lab in Nassau, Bahamas. The Panbio demonstrated a test sensitivity of 94% and a sp...

Neutralizing monoclonal antibodies (NAbs) with prophylactic and therapeutic efficacy have demonstrated fundamental importance in the control of SARS-CoV-2 transmission. However, their wide application has been largely limited by high cost and inconvenience in administration. Here, we developed an intranasal spray containing two synergetic human NAbs that could broadly neutralize the emerging Omicron variants in vitro. A unique synergetic neutralizing mechanism was identified that the two NAbs bo...

ObjectiveWe estimated the incidence rates (IRs) of respiratory syncytial virus (RSV)-related hospitalizations among adults aged [≥]60 years in Japan from 2015 to 2018, using a model-based approach to better understand the disease burden. MethodsWe obtained hospitalization data from the Medical Data Vision (MDV) database, restricted to Diagnosis Procedure Combination (DPC) hospitals. We estimated the annual age-specific RSV-attributable IR of hospitalizations for five cardiorespiratory outcom...

BackgroundIn 2024, there was quite high seroprevalence of anti-spike (S) protein antibodies against SARS-CoV-2 in Japanese adults, owing to the high vaccination coverage by spike-based vaccines. Nevertheless, the COVID-19 epidemic continues, albeit with low rates of severe illness, and hybrid immunity holders are becoming more common in these populations. It is necessary to determine the immunological protection correlates against SARS-CoV-2 re-infection in individuals with hybrid immunity becau...

The situation of the COVID-19 pandemic in Japan is drastically changing in the 2nd year, 2021, due to the appearance of SARS-CoV-2 variants of concern and the roll-out of mass vaccination. In addition to PCR diagnosis, periodic seroepidemiologic surveillance is important to analyze the epidemic situation. In this study, we analyzed the rate of seropositivity for the SARS-CoV-2 N and S antigens in Hyogo prefecture, Japan in August 2021. Sera collected from people who received a health check-up in...

COVID-19 vaccination campaign has been launched around the world. More than 8 billion vaccines doses have been administered, according to the WHO. Published studies shows that vaccination reduces the number of COVID-19 cases and dramatically reduces COVID-19-associated hospitalizations and deaths worldwide. In turn, the emergence of SARS-CoV-2 variants of concern (VOC) with mutations in the receptor-binding domain (RBD) of S glycoprotein poses risks of diminishing the effectiveness of the vaccin...

Background Self-sampling for SARS-CoV-2 would significantly raise testing capacity and reduce healthcare worker (HCW) exposure to infectious droplets personal, and protective equipment (PPE) use. Methods We conducted a diagnostic accuracy study where subjects with a confirmed diagnosis of COVID-19 (n=401) and healthy volunteers (n=100) were asked to self-swab from their oropharynx and mid-turbinate (OPMT), and self-collect saliva. The results of these samples were compared to an OPMT performed b...

BackgroundQuantifying the burden of respiratory syncytial virus (RSV) in adults is challenging compared to influenza, and data among older adults remain scarce in Japan. Country-specific evidence is essential to support RSV vaccination policy. MethodsThis prospective, multicenter study (APSG-J2) targeted hospitalized adults with community-acquired pneumonia (CAP) and other acute respiratory infection (ARI) in seven community-hospitals across four catchment areas in Japan between September 2022 ...