Purpose: Although some immune protection from close contact with individuals who have coronavirus disease 2019 (COVID-19) has been documented, there is limited data on the seroprevalence of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in individuals who were in lockdown with confirmed COVID-19 cases. This study investigated immunogenicity against SARS-CoV-2 in household members and people who lived near home-quarantined patients with COVID-19. Materials and Methods: This cross-sectional study was conducted during the community-based care that took place during lockdowns in District 10, Ho Chi Minh City, Vietnam from July to September 2021. SARS-CoV-2 antibody levels were determined in index cases of COVID-19, household contacts, and a no-contact group from the same area. Results: A total of 770 participants were included (355 index cases, 103 household contacts, and 312 no contacts). All index cases were unvaccinated, but >90% of individuals in the household and no-contact groups had received ≥1 vaccine dose. SARS-CoV-2 neutralizing antibodies (Nabs) were present in >77% of unvaccinated index cases versus 64%/65.4% in the householdo-contact groups (p=0.001). Antibody concentrations in unvaccinated index cases were significantly higher than those in household contacts and no contacts, with no difference between the latter groups. In all cases, antibody levels declined markedly ≥6 weeks after infection, and failed to persist beyond this time in the household and no-contact groups. Conclusion Community-based care may have helped to create community immunogenicity, but Nabs did not persist, highlighting a need for vaccination for all individuals before, or from 6 weeks after, infection with SARS-CoV-2.

Background: Vertebral fractures are the most common complication of osteoporosis, but more than two-thirds are asymptomatic. Therefore, the present study was conducted with the following objectives: (1) To describe some characteristics of incident asymptomatic vertebral fractures in adults aged 50 years and older in Vietnam; (2) To evaluate some factors related to incident asymptomatic vertebral fractures in adults aged 50 years and older in Vietnam. Materials and Methods: 455 adults aged 50 years and older volunteered to participate in the study. Cohort study of the Vietnam Osteoporosis Study (VOS) project. Results and Conclusions: In 29/455 cases of incident asymptomatic vertebral fractures followed after 2 years, the most common characteristics included: wedge fracture type (73.3%), grade 2 fracture (56.7%), and the most common locations are T12 and L1 (over 50%). Factors associated with incident vertebral fractures are advanced age and smoking.