In vitro neuraminidase inhibitory concentrations (IC50) of four neuraminidase inhibitors in the Japanese 2022-23 season: Comparison with the 2010-11 to 2019-20 seasons.

To assess the extent of susceptibility to the four neuraminidase inhibitors (NAIs) approved in Japan of the epidemic viruses in the 2022-23 influenza season in Japan, we measured the 50 % inhibitory concentration (IC50) of oseltamivir, zanamivir, peramivir, and laninamivir in influenza virus isolates from patients. Viral isolation was done with specimens obtained prior to and after treatment, and the type/subtype was determined by RT-PCR using type- and subtype-specific primers. The IC50 was determined by a neuraminidase inhibition assay using a fluorescent substrate. Virus isolates, one A(H1N1)pdm09 and 74 A(H3N2), were measured in the 2022-23 season. The geometric mean IC50s of the 74 A(H3N2) isolated prior to treatment were 0.78 nM, 0.66 nM, 2.08 nM, and 2.85 nM for oseltamivir, peramivir, zanamivir, and laninamivir, respectively, comparable to those of the previous ten studied seasons. No A(H3N2) with highly reduced sensitivity to any of the NAIs was found in the 2022-23 season prior to or after drug administration. These results indicate that the sensitivity to these four commonly used NAIs has been maintained, at least for A(H3N2), in the 2022-23 influenza season in Japan, after the 2020-21 and 2021-22 seasons when the prevalence of influenza was extremely low.

Successful perioperative management of a case of infective endocarditis secondary to a Lemierre's syndrome variant with severe neurological manifestations.

Lemierre's syndrome (LS) is characterized by septic thrombophlebitis of the internal jugular vein with septicemia and metastatic infection following an oropharyngeal infection. LS is rare but can cause infective endocarditis (IE), complicating IE management. We report a case of IE secondary to thrombophlebitis in the left vertebral vein following pharyngitis (LS variant) with distinctively severe manifestations, including metastatic infection and severe neurological impairment with multiple cerebral infarctions. A pedunculated abscess was noted on the left ventricular free wall. Despite the patient's highly impaired consciousness level (i.e., comatose state), we performed early surgery to remove the abscess after excluding LS-related brain complications. Preoperative antibiotics included clindamycin to cover LS-related anaerobic bacteria, and thrombophlebitis required postoperative anticoagulation. By managing LS as well as IE, the infection was controlled, and the neurological status normalized. This report provides insights into the perioperative management of IE secondary to LS.

Virological and clinical outcomes in outpatients treated with baloxavir or neuraminidase inhibitors for A(H3N2) influenza: A multicenter study of the 2022-2023 season.

While clinical trials have illuminated both the virological and clinical efficacy of baloxavir for influenza and post-treatment viral resistance, these aspects warrant further study in real-world settings. In response, we executed a prospective, observational study of the Japanese 2022-2023 influenza season. A cohort of 73 A(H3N2)-diagnosed outpatients-36 treated with baloxavir, 20 with oseltamivir, and 17 with other neuraminidase inhibitors (NAIs)-were analyzed. Viral samples were collected before and after administering an antiviral on days 1, 5, and 10, respectively. Cultured viruses were amplified using RT-PCR and sequenced to detect mutations. Fever and other symptoms were tracked via self-reporting diaries. In the baloxavir cohort, viral detection was 11.1% (4/36) and 0% (0/36) on day 5 and day 10, respectively. Two isolates from day 5 (5.6%, 2/36) manifested I38T/M-substitutions in the polymerase acidic protein (PA). For oseltamivir and other NAIs, viral detection rates were 60.0% (12/20) and 52.9% (9/17) on day 5, and 16.7% (3/18) and 6.3% (1/16) on day 10, respectively. No oseltamivir-resistant neuraminidase mutations were identified after treatment. Median fever durations for the baloxavir, oseltamivir, and other NAI cohorts were 27.0, 38.0, and 36.0 h, respectively, with no significant difference. Two patients harboring PA I38T/M-substitutions did not exhibit prolonged fever or other symptoms. These findings affirm baloxavir's virological and clinical effectiveness against A(H3N2) in the 2022-2023 season and suggest limited clinical influence of post-treatment resistance emergence.

Reduction of adverse reactions and correlation between post-vaccination fever and specific antibody response across successive SARS-CoV-2 mRNA vaccinations.

Background: SARS-CoV-2 mRNA vaccination, recognized for high immunogenicity, frequently induces adverse reactions, especially fever. We previously reported a correlation between post-vaccination fever and specific antibody responses to the primary series and first booster. We herein report changes in adverse reactions and the correlation between post-vaccination fever and antibody responses across successive vaccinations, from monovalent to bivalent mRNA vaccines. Methods: This cohort study was conducted at a Japanese hospital to investigate adverse reactions to the monovalent primary, first booster, and BA.4/5 bivalent BNT162b2 vaccinations. Local and systemic reactions were reported through a self-reporting diary after each dose. The spike-specific IgG titers were measured following each vaccination. Results: Across 727 vaccinations in the vaccine series, the bivalent booster induced fewer adverse reactions than earlier doses. Fever ≥ 38.0 °C was significantly less frequent in the bivalent booster (12.3 %) compared to the primary series and monovalent booster (22.0 %, 26.2 %, p < 0.001). Reaction severity was also reduced in the bivalent booster. In the analysis of 70 participants with complete data for all doses, post-vaccination fever ≥ 38.0 °C exhibited the highest relative risk (RR) among all solicited reactions throughout the vaccine series (RR: 5.24 [95 % CI: 2.40-11.42] for monovalent and 6.24 [95 % CI: 2.14-18.15] for bivalent). The frequency of fever ≥ 38.0 °C after all doses was 8.6 % (6/70), with no fever ≥ 39.0 °C across all vaccinations. A high-grade post-vaccination fever was correlated with higher IgG titers, with multivariate analyses confirming this correlation as independent for each dose and unaffected by previous post-vaccination fever. Conclusions: The bivalent mRNA vaccine booster showed fewer and milder adverse reactions than the monovalent doses. Although vaccinees with a history of post-vaccination fever were more likely to experience fever after a subsequent dose, such recurrences were infrequent. A correlation between post-vaccination fever and increased IgG titers was identified for each vaccination, irrespective of post-vaccination fever history.

Distinct features of SARS-CoV-2 humoral immunity against Omicron breakthrough infection.

BACKGROUND: SARS-CoV-2 Omicron breakthrough infection (Omicron-BTI) after vaccination has been frequently observed. A more detailed understanding of the humoral immunity against Omicron-BTI is required. METHODS: We measured strain-specific live-virus based neutralizing activity, anti-spike IgG, and anti-receptor-binding domain (RBD) IgG titers in individuals with Omicron/BA.1-BTI and directly compared them with controls with diverse combinations of wild-type (WT) mRNA vaccination and infection history. RESULTS: Omicron-BTI individuals showed markedly higher neutralizing titers against all the WT, Delta, and Omicron strains in convalescent sera, compared with unvaccinated Omicron-infection individuals with only Omicron neutralizing activity. Similar tendencies were found in strain-specific anti-spike and anti-RBD IgG titers. The Omicron-specificity (BA.1/WT neutralizing ratio), Omicron-neutralizing efficiency per antibody unit, and anti-Omicron RBD-directivity of anti-spike antibodies in Omicron-BTI individuals were all significantly lower than those in unvaccinated Omicron-infection individuals, but they were equivalent to or higher than those in uninfected vaccinees. The induction of Omicron-specific neutralizing activity after Omicron-BTI was not weakened for eight months from the last vaccination. CONCLUSIONS: These findings suggest that cross-reactive vaccine-induced immunity was intensively stimulated following Omicron breakthrough infection, which contributed to Omicron neutralization. Measuring SARS-CoV-2 variant-specific antibody levels as well as neutralizing activity is useful for evaluating humoral immunity after breakthrough infection in the current situation of antigenic gaps between vaccinated and epidemic (Omicron sub-lineages) strains.

Achievement of sufficient antibody response after a fourth dose of wild-type SARS-CoV-2 mRNA vaccine in nursing home residents.

BACKGROUND: Infection control during COVID-19 outbreaks in nursing facilities is a critical public health issue. Antibody responses before and after the fourth (second booster) dose of wild-type severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine in nursing home residents have not been fully characterized. METHODS: This study included 112 individuals: 54 nursing home residents (mean age: 84.4 years; 35 SARS-CoV-2-naive and 19 previously infected) and 58 healthcare workers (mean age: 47.7 years; 25 SARS-CoV-2-naive and 33 previously infected). Antispike and antinucleocapsid antibody responses to messenger RNA vaccination were evaluated using serum samples collected shortly and 5 months after the third dose, and shortly after the fourth dose. RESULTS: The median immunoglobulin G (IgG) level in SARS-CoV-2-naive residents was similar to that in SARS-CoV-2-naive healthcare workers after the fourth dose (24,026.3 vs. 30,328.6 AU/mL, p = .79), whereas after the third dose the IgG level of SARS-CoV-2-naive residents was approximately twofold lower than that in SARS-CoV-2-naive healthcare workers. In residents with previous SARS-CoV-2 infection, timing of infection in relation to vaccination affected the kinetics of antibody responses. Residents infected after the third dose showed the highest IgG levels after the fourth dose among all groups (median: 64,328.8 AU/mL), in contrast to residents infected before initiating vaccination with antibody levels similar to those of SARS-CoV-2-naive residents. CONCLUSIONS: Advanced aged nursing home residents, poor responders in the initial SARS-CoV-2 vaccine series, could achieve sufficient antibody responses after the fourth (second booster) vaccination, comparable to those of younger adults.

Correlation between specific antibody response to wild-type BNT162b2 booster and the risk of breakthrough infection with omicron variants: Impact of household exposure in hospital healthcare workers.

BACKGROUND: The emergence of omicron variants exhibiting antigenic changes has led to an increase in breakthrough infection among individuals with a wild-type SARS-CoV-2 vaccine booster. The correlation between post-booster spike-specific antibodies and omicron infection risk remains unclear. METHODS: This prospective cohort study included SARS-CoV-2-naive healthcare workers with three-dose BNT162b2. Post-booster spike-specific IgG and interferon-γ levels were measured. Breakthrough infection was documented during a 10-month omicron-predominant period. Household and healthcare contacts were followed to identify subsequent infections. The IgG titers were additionally measured at the end of follow-up, and the titers at exposure were estimated from the two-point titers. RESULTS: Of 333 participants, 89 developed infection, of whom 37 (41.6 %) were household contacts. Kaplan-Meier curves indicated that higher IgG titers were significantly correlated with lower cumulative infection incidence (p = 0.029), whereas the interferon-γ levels were not (p = 0.926). Multivariate Cox analysis showed that increasing IgG titers were associated with a reduced hazard ratio (HR) of 0.26 (95% CI, 0.12-0.55). Household exposure posed a greater infection risk than healthcare exposure (HRs, 11.24 [6.88-18.40] vs. 2.82 [1.37-5.44]). The difference in geometric mean IgG titers of infected and uninfected participants was significant among household contacts (20,244 AU/mL vs. 13,842 AU/mL, p = 0.031). Estimation of IgG titers at exposure showed a significantly higher infection incidence in those exposed with titers of <3,000 AU/mL than in those with higher titers (79.2 % vs. 32.3 %, p < 0.001). CONCLUSIONS: Spike-specific antibodies induced by a wild-type SARS-CoV-2 vaccine booster are suggested to be effective in protecting against omicron infection. Household exposure would be a significant source of infection for hospital healthcare workers.

SARS-CoV-2 strain-specific anti-spike IgG ELISA utilizing spike protein produced by silkworms.

BACKGROUND: A cost-effective and eco-friendly method is needed for the assessment of humoral immunity against SARS-CoV-2 in large populations. OBJECTIVE: We investigated the performance of an ELISA that uses silkworm-produced proteins to quantify the strain-specific anti-Spike IgG (anti-S IgG) titer. METHODS: The OD values for the anti-His-tag antibody, a standard material of ELISA quantification, were measured. Correlations between the ELISA for each strain and the Abbott SARS-CoV-2 IgG II Quant assay for the wild type were evaluated with serum samples from nine participants with various infection and vaccination statuses. RESULTS: Linear dose-responses were confirmed by high coefficients of determination: 0.994, 0.994, and 0.996 for the wild-type, Delta, and Omicron (BA.1) strain assays, respectively. The coefficient of determination for the wild-type and Delta strain assays was high at 0.959 and 0.892, respectively, while the Omicron strain assay had a relatively low value of 0.563. Booster vaccinees showed similar or higher titers against all strains compared to infected persons without vaccination. The Omicron-infected persons without vaccination had lower antibody titers against wild type than did the vaccinated persons. CONCLUSIONS: This study provides data indicating that the ELISA with silkworm-produced proteins makes it possible to discriminate and quantify the strain-specific anti-S IgG antibody induced by vaccination or infection.

Pronounced antibody elevation after SARS-CoV-2 BNT162b2 mRNA booster vaccination in nursing home residents.

BACKGROUND: Infection control during COVID-19 outbreaks in nursing facilities is a critical public health issue. Antibody responses before and after the third (booster) dose of SARS-CoV-2 vaccination in nursing home residents have not been fully characterized. METHODS: This study included 117 individuals: 54 nursing home residents (mean age, 83.8 years; 39 SARS-CoV-2-naive and 15 previously infected) and 63 healthcare workers (mean age, 45.8 years; 32 SARS-CoV-2-naive and 31 previously infected). Anti-spike (receptor-binding domain [RBD]) and anti-nucleocapsid antibody responses to BNT162b2 mRNA vaccination and their related factors were evaluated using pre- (shortly and 6 months after the second dose) and post-booster vaccination samples. RESULTS: The median anti-spike (RBD) IgG level in SARS-CoV-2-naive residents 6 months after the second dose was the lowest among the four groups, with a decreasing rate of over 90%. The median rate of increase before and after the third dose in SARS-CoV-2-naive residents was significantly higher than that in SARS-CoV-2-naive healthcare workers (64.1- vs. 37.0-fold, P = 0.003), with the highest level among the groups. The IgG ratio of SARS-CoV-2-naive residents to healthcare workers after the second and third doses changed from one-fifth (20%) to one-half (50%). The rate of increase after the third dose in previously infected individuals was three- to fourfold, regardless of residents or healthcare workers. CONCLUSIONS: Advanced aged nursing home residents, poor responders in the initial SARS-CoV-2 vaccine series, could obtain sufficient antibody responses with the additional booster dose, despite more than 6 months after the second.

Post-vaccination antibody evaluation for nosocomial SARS-CoV-2 delta variant breakthrough infection.

Waning humoral immunity after mRNA vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a significant problem for public health. Breakthrough infection in hospitals over several months after vaccination has not been fully characterized, especially against the delta (B.1.617.2) variant. Here, we describe an outbreak in our hospital in September of 2021, mainly through serological evaluation of the breakthrough infection. This retrospective observational study was done at an emergency and acute care hospital with 204 beds and 486 staff members where most staff members (92.6%) had had their second BNT162b2 vaccination by May of 2021. The peri-infection anti-spike RBD protein IgG (anti-S IgG) titers (lowest values between 11 days before and 7 days after onset or diagnosis) of serum samples from the breakthrough-infected persons were quantified. We also logarithmically estimated the anti-S IgG titers during the exposure period in September of uninfected staff members from their samples collected in May and December 2021. Whole-genome sequencing was done on obtained samples. In this outbreak, twelve persons (ten inpatients and two staff members) were diagnosed with SARS-CoV-2 infection by Loop-Mediated Isothermal Amplification (LAMP) or RT-PCR, eight of whom had been vaccinated twice. Peri-infection anti-S IgG titers could be determined in seven of the eight breakthrough cases, with a geometric mean titer (GMT) of 1,034 AU/ml (95% confidence interval [CI], 398 to 2,686). Among 289 uninfected staff members with data from the two sampling points, the GMT of the estimated anti-S IgG titers during the exposure period in 51 staff members, who were working at the outbreak ward and potentially exposed but uninfected, and 238 other unexposed staff members were 1,458 AU/ml (95% CI, 1,196 to 1,777) and 1,628 AU/ml (95% CI, 1,500 to 1,766), respectively. All viruses from the eight samples for which whole-genome sequencing was available were identified as delta variants. Of the infected persons, one remained asymptomatic throughout the course of treatment, and eleven had an illness of mild to moderate severity, including ten who received monoclonal antibody cocktail (Casirivimab/imdevimab) therapy. Measurement and estimation of anti-spike antibody levels after SARS-CoV-2 vaccination would be helpful for evaluating the risk of breakthrough infection and for determining the necessity of booster vaccination.

Relation of fever intensity and antipyretic use with specific antibody response after two doses of the BNT162b2 mRNA vaccine.

BACKGROUND: The reactogenicity of BNT162b2 COVID-19 vaccine has been commonly reported and antipyretic medications are often used for mitigating adverse reactions. Possible associations between the reactogenicity events and specific antibody responses have not been fully investigated, nor has the influence of using antipyretics. METHODS: Serum samples were collected from hospital healthcare workers with no COVID-19 history and the SARS-CoV-2 spike-specific IgG titer after two doses was measured. Degree of solicited adverse reactions in a day, including the highest body temperature, were reported using a self-reporting diary for five days after each dose. The highest body temperature during the five days was divided into three grades (<37.0 °C, 37.0-37.9 °C, or ≥ 38.0 °C). Self-medicated antipyretics were reported using a questionnaire. RESULTS: The data of 335 participants were available for analysis. Multivariate analysis extracted the fever grade after the second dose (standardized coefficient beta = 0.301, p < 0.0001), female sex (beta = 0.196, p = 0.0014), and age (beta = -0.119, p = 0.0495) as being significantly correlated with the IgG titers. The positive correlation of the fever grade after the second dose with the IgG titers was also observed when analyzed by sex and age. The use of antipyretics did not interfere with the IgG titers irrespective of the fever grade. CONCLUSIONS: The fever intensity after the second dose was associated with the IgG titer and antipyretic medications may be beneficial to mitigate the suffering from adverse reactions, without interfering with the acquisition of sufficient antibody responses.

No significant influence of pre-vaccination antipyretic use on specific antibody response to a BNT162b2 vaccine booster against COVID-19.

The relation between pre-vaccination antipyretic use and antibody responses to SARS-CoV-2 vaccination has been unclear. We measured the pre- and post-BNT162b2 booster spike-specific IgG titers and recorded antipyretic use and adverse reactions for SARS-CoV-2-naive hospital healthcare workers. The data of 20 cases who used antipyretics within 24 h before vaccination were compared to that of 281 controls. The post-booster geometric mean IgG titers were 15,559 AU/mL (95 % CI, 11,474-21,203) for the cases and 16,850 AU/mL (95 % CI, 15,563-18,243) for the controls (p = 0.622). No significant reduction in the frequency or severity of any of the solicited adverse reactions was found for the cases. Similar results were obtained after adjustment with propensity-score matching for demographic characteristics, baseline IgG titer, and post-vaccination antipyretic use. Antipyretic use within 24 h before vaccination would not affect mRNA COVID-19 vaccine-induced specific antibody responses and that postponement of vaccination due to pre-vaccination antipyretic use would be unnecessary.

Correlation of Postvaccination Fever With Specific Antibody Response to Severe Acute Respiratory Syndrome Coronavirus 2 BNT162b2 Booster and No Significant Influence of Antipyretic Medication.

Background: A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccine booster elicits sufficient antibody responses that protect against coronavirus disease 2019, whereas adverse reactions such as fever have been commonly reported. Associations between adverse reactions and antibody responses have not been fully characterized, nor has the influence of antipyretic use. Methods: This is a prospective observational cohort study in Japan, following our prior investigation of BNT162b2 2-dose primary series. Spike-specific immunoglobulin G (IgG) titers were measured for SARS-CoV-2-naive hospital healthcare workers who received a BNT162b2 booster. The severity of solicited adverse reactions, including the highest body temperature, and self-medicated antipyretics were reported daily for 7 days following vaccination through a web-based self-reporting diary. Results: The data of 281 healthcare workers were available. Multivariate analysis extracted fever after the booster dose (ß = .305, P < .001) as being significantly correlated with the specific IgG titers. The analysis of 164 participants with data from the primary series showed that fever after the second dose was associated with the emergence of fever after the booster dose (relative risk, 3.97 [95% confidence interval, 2.48-6.35]); however, the IgG titers after the booster dose were not associated with the presence or degree of fever after the second dose. There were no significant differences in the IgG titers by the use, type, or dosage of antipyretic medication. Conclusions: These results suggest an independent correlation between mRNA vaccine-induced specific IgG levels and post-booster vaccination fever, without any significant influence of fever after the primary series. Antipyretic medications for adverse reactions should not interfere with the elevation of specific IgG titers.