An early return-to-work program for COVID-19 close contacts in healthcare during the Omicron wave in Japan

During the coronavirus disease 2019 (COVID-19) pandemic, maintaining adequate staffing in healthcare facilities is important to provide a safe work environment for healthcare workers (HCWs). Japan's early return-to-work (RTW) program may be a rational strategy at a time when there is an increased demand for the services of HCWs. We assessed whether the early RTW program for HCWs who have been in close contact with a COVID-19 case in our hospital was justified. Close contacts were identified according to the guidance document of the World Health Organization. HCWs who met all of the following conditions were eligible to apply to an early RTW program: (1) difficult to replace with another HCW, (2) received the third dose of a COVID-19 mRNA vaccine, (3) a negative COVID-19 antigen test before each work shift, and (4) consent from relevant HCWs and their managers to participate in the program. Between January and March 2022, 256 HCWs were identified as close contacts (median age, 35 years;192 female). Thirty-seven (14%) secondary attack cases of COVID-19 were detected. Among 141 HCWs (55%) who applied to the early RTW program, nurses and physicians comprised about three-quarters of participants, with a higher participation rate by physicians (78%) than nurses (59%). Eighteen HCWs tested positive for COVID-19 by the sixth day after starting the early RTW program. No COVID-19 infection clusters were reported during the observation period. These findings suggest that the early RTW program for COVID-19 close contacts was a reasonable strategy for HCWs during the Omicron wave.

Antibody Responses to BNT162b2 Vaccination in Japan: Monitoring Vaccine Efficacy by Measuring IgG Antibodies against the Receptor-Binding Domain of SARS-CoV-2.

To fight severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), mass vaccination has begun in many countries. To investigate the usefulness of a serological assay to predict vaccine efficacy, we analyzed the levels of IgG, IgM, and IgA against the receptor-binding domain (RBD) of SARS-CoV-2 in the sera from BNT162b2 vaccinated individuals in Japan. This study included 219 individuals who received two doses of BNT162b2. The levels of IgG, IgM, and IgA against RBD were measured by enzyme-linked immunosorbent assay before and after the first and second vaccination, respectively. The relationship between antibody levels and several factors, including age, gender, and hypertension were analyzed. Virus-neutralizing activity in sera was measured to determine the correlation with the levels of antibodies. A chemiluminescent enzyme immunoassay (CLEIA) method to measure IgG against RBD was developed and validated for the clinical setting. The levels of all antibody isotypes were increased after vaccination. Among them, RBD-IgG was dramatically increased after the second vaccination. The IgG levels in females were significantly higher than in males. There was a negative correlation between age and IgG levels in males. The IgG levels significantly correlated with the neutralizing activity. The CLEIA assay measuring IgG against RBD showed a reliable performance and a high correlation with neutralizing activity. Monitoring of IgG against RBD is a powerful tool to predict the efficacy of SARS-CoV-2 vaccination and provides useful information in considering a personalized vaccination strategy for COVID-19. IMPORTANCE Mass vaccination campaigns using mRNA vaccines against SARS-CoV-2 have begun in many countries. Serological assays to detect antibody production may be a useful tool to monitor the efficacy of SARS-CoV-2 vaccination in individuals. Here, we reported the induction of antibody isotype responses after the first and second dose of the BNT162b2 vaccine in a well-defined cohort of employees in Japan. We also reported that age, gender, and hypertension are associated with differences in antibody response after vaccination. This study not only provides valuable information with respect to antibody responses after BNT162b2 vaccination in the Japanese population but also the usefulness of serological assays for monitoring vaccine efficacy in clinical laboratories to determine a personalized vaccination strategy for COVID-19.

Immunogenicity of BNT162b2 mRNA COVID-19 Vaccine in Patients with Cardiovascular Disease.

Concern has been raised about the effectiveness of the coronavirus disease 2019 (COVID-19) vaccine in the population of patients with various comorbidities such as heart disease. We investigated the humoral response to the BNT162b2 mRNA COVID-19 vaccine in patients with cardiovascular disease (CVD). We measured IgG against severe acute respiratory syndrome coronavirus 2 spike receptor-binding domain (RBD-IgG) in 85 CVD patients and 179 healthcare workers (HCWs). Blood samples were collected from patients and HCWs three times: (1) before the first dose of vaccination, (2) two weeks after the first dose of vaccination, and (3) two weeks after the second dose of vaccination. Patients with CVD showed a significantly inferior serological response to the BNT162b2 mRNA COVID-19 vaccine at 14 days after the prime dose compared to HCWs (21% vs. 95%, p < 0.001). Median RBD-IgG titers of patients with CVD at 14 days after the second dose were significantly lower than those of HCWs (137.2 U/mL (80.6-200.4 U/mL) vs. 176.2 U/mL (123.9-260.0 U/mL), p < 0.001). In multivariable analyses, CVD is significantly associated with seropositivity after first vaccination and RBD-IgG titers after second vaccination. CVD patients may have a poor humoral response to the BNT162b2 mRNA COVID-19 vaccine, need to be closely monitored, and require earlier revaccination to ensure stronger immunity and protection against infection.