COVID-19 vaccines have demonstrated efficacy in reducing the prevalence of serious illnesses. The relative risk of hospitalization and mortality for patients who get breakthrough infections after immunization versus those who develop reinfections after a prior spontaneous infection is examined in this correspondence. Based on a study on U.S. Veterans who were not vaccinated and experienced reinfections had a much higher risk of experiencing severe illness outcomes compared to those who had received immunizations and experienced breakthrough infections, even if the rates of reinfection and breakthrough infection were similar. Our findings highlight the value of immunization in reducing severe COVID-19 outcomes, even in the presence of reinfections.

Background: Severe COVID-19 patients who received ventilator management were not very rare even when the omicron variant became dominant, but the clinical characteristics of these patients are still unclear. Methods: The clinical characteristics of severe COVID-19 patients requiring ventilator management were retrospectively investigated from January 2023 to December 2023. Results: Severe COVID-19 patients who received ventilator management accounted for 11 of 275 (4.2%) patients during the omicron variant period. Their mean age was 70.7 (51-85) years, and males were predominant. Ten of eleven (91.7%) patients were managed in the emergency department and had underlying diseases, including chronic lung/heart/kidney diseases and neurological diseases. However, only 4 of 11 (36.4%) had a clear history of vaccination. The patients showed a positive SARS-CoV-2 antigen titer of 3305.7 (12.9-20912). All 11 patients were treated with remdesivir and dexamethasone, and 5 (45.5%) also received sotrovimab. Pathogenic bacteria were isolated from 7 of 11 (63.6%) patients, and all 11 patients were treated with antibiotics. Only 3 of 11 (27.3%) patients were managed using extracorporeal membrane oxygenation (ECMO), but 9 of 11(81.8%) patients survived. Conclusions: These data suggest that severe COVID-19 patients who required ventilator management were less-vaccinated, elderly patients with underlying disease. These patients were treated successfully using antiviral agents, steroids, neutralizing antibodies, and antibiotics, with a few also treated using ECMO in the omicron era.

Background: The titers of SARS-COV-2 antigens are frequently used as markers of viral activity and threshold for release from quarantine and treatment. COVID-19 patients were treated with several antiviral agents, including remdesivir (RDV) and ensitrelvir (ESV), which is a novel anti-SARS-CoV-2 agent recently suggested to have strong antiviral activity. Cases: We present the cases of two patients whose SARS-CoV-2 antigens were successfully decreased by oral administration of ESV after they could not be decreased by RDV drip infusion. Case 1 was a 74-year-old man who was admitted with SARS-CoV-2 infection and had been infected by the virus a month earlier and relapsed twice. He had been treated with rituximab for diffuse B cell lymphoma and not received vaccination for SARS-CoV-2. RDV was administered intravenously two weeks earlier and again 4 days earlier, but it failed to control the infection, and he was transferred to our hospital (day 1). Intravenous RDV was restarted on day 1, but viral antigens remained high until day 5. The RDV was then switched to oral ESV, and viral antigen titers were successfully decreased on days 8, 10, and 12. Case 2 was an 81-year-old man who was admitted with SARS-CoV-2 infection on day 0. He had heart failure and diabetes mellitus, and had not received vaccination for SARS-CoV-2. Intravenous RDV was started on day 1, but viral antigens were still high until day 8. He was then switched from RDV to oral ESV, and viral antigen titers were successfully decreased on day 11. Conclusions: These cases suggest that ESV might be more effective than RDV for reducing viral activity, and it is easy to administer orally.

The pulmonary characteristics of Staphylococcus aureus (S. aureus) co-infection with respiratory viruses, such as SARS-CoV-2 and influenza virus, are still unclear. Case series: Two patients with methicillin-susceptible S. aureus (MSSA) infection in the lungs co-infected with either SARS-CoV-2 or influenza virus are reported. Case 1 was a 66-year-old woman who was admitted with SARS-CoV-2 infection. Her chest X-ray and computed tomography (CT) showed multiple cavity formations with infiltration shadows, and MSSA was detected from her sputum and blood, suggesting COVID-19-related bacterial pneumonia and pulmonary embolism. No catheters had been used, but she had skin eruptions and a history of SARS-CoV-2 vaccination. Ampicillin/sulbactam (ABPC/SBT) was administered, and she finally improved. Case 2 was an 87-year-old man with a history of atopic dermatitis who was admitted with moderate pneumonia, and influenza virus co-infection was found. He showed multiple cavitary shadows, and MSSA was isolated from both his sputum and blood. He was diagnosed with influenza-related bacterial pulmonary embolism. No catheters had been used, but he had a history of influenza vaccination. He was also treated by ABPC/SBT and finally improved. Conclusions: These cases suggest that MSSA showed affinity to the lungs when co-infected with either SARS-CoV-2 or influenza virus, and it presented as septic emboli without catheter use. We should consider MSSA infection when patients have SARS-CoV-2 or influenza virus co-infection, and multiple cavity formation and skin disorders are seen, even though they were vaccinated and no catheters were used.