Optimal Inhalation Profile of Pressurized Metered Dry Powder Inhaler Using a Valved Holding Chamber: A Dynamic Analysis.

Background: The combined use of a pressurized metered-dose inhaler and valved holding chamber (pMDI+VHC) is recommended to improve efficiency and safety; however, aerosol release is likely to vary with the inhalation maneuver. This in vitro study investigated the aerodynamic characteristics and aerosol release features of pMDI+VHC (Aerochamber, Trudell Medical International). Methods: The static and dynamic changes in the airway resistance (Raw) during inhalation (withdrawal) through pMDI+VHC were measured. Subsequently, the aerosol released from pMDI+VHC was measured using simplified laser photometry during withdrawal with either fast ramp-up then steady or slow ramp-up followed by gradual decrement at different intensities and times to peak flow (TPWF). Results: Raw increased linearly with changes in the withdrawal flow (WF) rate between 10 and 50 L/min. The slope was steep in the low WF range (<50 L/min) and became milder in the higher range. The aerosol mass tended to increase with an increase in the peak WF (PWF) of slow ramp-up profile. When three different WF increment slopes (TPWF: 0.4, 1.4, and 2.4 seconds) were compared, the released aerosol mass tended to decrease, and the aerosol release time was prolonged at longer TPWF. When the PWF was increased, the aerosol release time became shorter, and the withdrawn volume required for 95% aerosol release became larger; however, it did not exceed 0.4 L at suitable TPWF (0.4 seconds). Conclusion: Raw analysis suggests that inhalation at 30-50 L/min is suitable for pMDI+VHC in this setting. Rapid (TPWF, 0.4 seconds) inhalation, but not necessarily long (maximum 2.0 seconds) and deep (but larger than 0.55 L), is also recommended. Practically, direct inhalation to be weaker than usual breathing, as fast as possible, and far less than 2.0 seconds.

Antibody Responses to the BNT162b2 mRNA Vaccine in Healthcare Workers in a General Hospital in Japan: A Comparison of Two Assays for Anti-spike Protein Immunoglobulin G.

Objective This study assessed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses to the BNT162b2 mRNA vaccine in Japanese healthcare workers. Methods In this prospective cohort study, participants received two doses of the BNT162b2 mRNA vaccine on days 0 and 21 and provided blood for anti-SARS-CoV-2 antibody testing before the first vaccine and on days 21 and 35 after vaccination. Anti-spike protein immunoglobulin G (S-IgG) was measured using Abbott and Fujirebio chemiluminescent immunoassays. Patients One hundred healthcare workers (median age: 39 years old, interquartile range: 30-48 years old), including 6 who had been previously infected with SARS-CoV-2 and 3 individuals taking immunosuppressive drugs, participated in the study. Results The S-IgG antibody titers (AU/mL) measured using both the Abbott and Fujirebio assays increased significantly (p<0.001) over time, both with a prevalence of 100% at 35 days after the first vaccination. The multivariate log-normal linear regression analysis indicated the effect of immunosuppressant medication using both the Abbott (p=0.013) and Fujirebio (p=0.039) assays on S-IgG levels after complete vaccination. Pearson's correlation coefficient between the Abbott and Fujirebio S-IgG results in all 300 samples collected before and after vaccination and 50 positive controls from patients with coronavirus disease 2019 were 0.963 [95% confidence interval (CI): 0.954-0.970, p<0.001] and 0.909 (95% CI: 0.845-0.948, p<0.001), respectively. Conclusion The BNT162b2 mRNA vaccine was effective at increasing S-IgG levels in Japanese immunocompetent healthcare workers. The Fujirebio S-IgG assay showed high diagnostic accuracy, using the Abbott S-IgG assay as the reference test.

Antibody responses to SARS-CoV-2 nucleocapsid and spike proteins in hospitalized patients with COVID-19: A multicenter, retrospective, cross-sectional study in Japan.

BACKGROUND: There are many commercially available automated assays for assessing coronavirus disease 2019 (COVID-19) immune responses; however, owing to insufficient data, their validities remain unknown. Here, we examined antibody responses during acute-phase COVID-19 using four assays that detect anti-spike protein IgM (S-IgM), anti-nucleocapsid protein IgG (N-IgG), anti-spike protein total Ig (S-total Ig), and anti-spike protein IgG (S-IgG). METHODS: We measured antibody levels in 1154 serum samples collected from 286 hospitalized patients with confirmed COVID-19 by a gene amplification method between February and December 2020 in Japan. Sera from 860 healthcare workers were used as negative controls. RESULTS: The antibody positivity rates increased on week 2, peaked, and then started to plateau by the beginning of week 3 after symptom onset. On week 1, there were some significant differences in seropositivity rates between assays (p = 0.032): 14.9% (11.0%-19.4%) for S-IgM and 8.9% (6.0%-12.7%) for N-IgG. The seropositivity for the S-total Ig (10.6% [7.3%-14.6%]) assay was considerably better than that for the S-IgG (6.9% [4.3%-10.4%]) assay, although the difference was not statistically significant (p = 0.150). The levels of S-IgM antibodies and the three others peaked on weeks 3 and 5, respectively. All four assays showed high specificities (>99%). CONCLUSIONS: All four assays had good specificities and were suitable for seropositivity detection after week 3 of symptom onset. Assays of IgM alone or total Ig (containing IgM) were better than those of IgG alone as an adjunct serological test for early-stage COVID-19 diagnosis, albeit the use of a serological assay alone is insufficient.