While mRNA vaccines against COVID-19 have shown progressively reduced effectiveness in preventing infection due to a mismatch between the antigen strain of the vaccine and the circulating strains, it has been reported that they maintain a certain level of effectiveness in preventing hospitalization and severe outcomes. There are few reports on the impact of times a subject is vaccinated (hereinafter, number of vaccinations) on the duration of fever and symptoms in patients with mild COVID-19. In this study, we distributed questionnaires to patients diagnosed as having COVID-19 and their families at outpatient clinics in three medical institutions in Ishikawa Prefecture during the period of spread of the Omicron variant of SARS-CoV-2 and conducted a retrospective analysis of the background information of the patients and the pattern of progression of their symptoms after the diagnosis. We conducted a multivariate analysis of the data of 501 adults with mild symptoms of COVID-19 to determine the factors affecting the highest body temperature during the course of infection, the duration of fever, and the rates of symptom persistence beyond 7, 14, and 30 days. Background factors and vaccination history were used as the explanatory variables. Patients who developed COVID-19 after receiving the vaccine three or more times showed a significantly lower maximum body temperature during the illness and a shorter duration of fever than those who developed the infection after receiving the vaccine once or twice. Furthermore, a trend towards milder and shorter duration of fever was observed as the number of vaccinations increased. Although a trend toward lower rates of symptom persistence other than fever was observed as the number of vaccinations increased, no significant differences were found according to the number of vaccinations. The data support booster vaccinations as being useful for reducing the degree and duration of fever in adult patients with mild symptoms of COVID-19 and suggest the possibility of higher effectiveness of a higher number of vaccinations.

Background: This study was aimed at assessing the epidemiology of secondary infection among hospital staff in close contact with primary infected patients and associated factors during the severe acute respiratory syndrome coronavirus 2 omicron variant pandemic.

Subjects and Methods: We conducted a retrospective survey of the secondary infection rate, sources of exposure, and interval to onset among hospital staff who were in close contact with the infected patients in 2022. Multivariate analysis was performed to identify predictors of the establishment of secondary infection from children, using the sex and age of the children (elementary school or younger vs. junior high school or older), number of vaccination doses, and interval between the last vaccination dose and exposure of the staff members as the explanatory variables.

Results: We identified 524 close contacts. The exposure sources were 283 children, 92 spouses/domestic partners, and 53 others among the cohabitants, and 83 family members/friends/coworkers and 13 COVID-19 positive patients among non-cohabitants. The age of the children as the exposure sources was known for 275 children, and a median age of 11 years (range: 0-40 years). Secondary infections were found in 122 staff members (122/524: 23.3%). The highest rate of secondary infection (infection rate) was from children (elementary school age or younger: 56,37.8%; junior high school age or older: 19, 15.0%; and unknown age: 2), spouses/domestic partners (32, 34.8%), and others (9, 17.3%), and non-cohabitant family/friends/colleagues (4, 4.8%). The median interval between exposure and disease onset was 4 days. Multivariate analysis showed a significant association between the age of the children, especially children of elementary school age or younger, and the establishment of secondary infection.

Conclusion: Secondary infections during the omicron variant epidemic were mostly household infections and were significantly associated with exposure to infected children, especially children of elementary school age or younger.

A 43-year-old man visited our hospital with a history of fever, rashes, and a mass in the right inguinal region. Tests for syphilis, namely, the rapid plasma regain test and a Treponema pallidum antibody test, ordered by his primary physician returned positive results. The patient was referred to the Division of Infectious Diseases for an expert review following the diagnosis of syphilis. The infectious diseases physician noticed an additional important symptom, namely, tinnitus during his [or 'her' ] medical chart review. Therefore, we suspected concomitant otosyphilis and performed lumbar puncture to check the cerebrospinal fluid for evidence of neurosyphilis. Analysis of the cerebrospinal fluid revealed evidence of meningeal inflammation. A consult was sent to the otolaryngologist, who made the diagnosis of endolymphatic hydrops due to syphilis. We treated the patient with a 2-week course of intravenous antibiotics (ceftriaxone followed by benzylpenicillin), in addition to systemic corticosteroids. With this treatment, all the symptoms improved and the rapid plasma reagin titer decreased. In Japan, the standard treatment for syphilis is intramuscular benzylpenicillin or oral amoxicillin. However, intravenous benzylpenicillin is recommended for the treatment of neurosyphilis, ocular syphilis, and otosyphilis. It is crucial for clinicians to consult experts when encountering patients with positive test results for syphilis who present with inner ear symptoms, for prompt and accurate diagnosis and selection of the appropriate treatment.

The purpose of this study was to compare the risk of development of secondary COVID-19 infection in healthcare workers during vaginal delivery versus during cesarean section. The study was conducted at two medical institutions, Hospital A and B, which attended to both types of deliveries in pregnant women with COVID-19. The COVID-19 incidence rates among the healthcare workers attending to the deliveries were compared retrospectively. The results showed that out of 27 healthcare workers in Hospital A, 9 tested positive for COVID-19, while in Hospital B, out of 62 workers, 7 tested positive for COVID-19. The incidence rate was higher in Hospital A, with a 3.86-fold higher odds ratio (95%CI: 1.10-14.2, p = 0.0181). However, after adjusting for the vaccination rate and age, no statistically significant difference in the rates was observed. Therefore, we concluded that vaginal delivery does not pose a higher risk of secondary COVID-19 infection in healthcare workers as compared with cesarean section.