Immune Persistence against SARS-CoV-2 after Primary and Booster Immunization in Humans: A Large-Scale Prospective Cohort Study.

Amid the ongoing global COVID-19 pandemic, limited literature exists on immune persistence after primary immunization and the immunogenic features of booster vaccines administered at different time intervals. Therefore, this study aimed to determine the immune attenuation of neutralizing antibodies against the SARS-CoV-2 wild-type strain, and Delta and Omicron variants 12 months after the primary administration of the COVID-19 inactivated vaccine and evaluate the immune response after a booster administration at different time intervals. A total of 514 individuals were followed up after primary immunization and were vaccinated with a booster. Neutralizing antibodies against the wild-type strain and Delta and Omicron variant spike proteins were measured using pseudovirus neutralization assays. The geometric mean titers (GMTs) after the primary and booster immunizations were 12.09 and 61.48 for the wild-type strain, 11.67 and 40.33 for the Delta variant, and 8.51 and 29.31 for the Omicron variant, respectively. The GMTs against the wild-type strain declined gradually during the 12 months after the primary immunization, and were lower against the two variants. After implementing a booster immunization with a 6 month interval, the GMTs against the wild-type strain were higher than those obtained beyond the 7 month interval; however, the GMTs against the two variants were not statistically different across 3-12 month intervals. Overall, SARS-CoV-2 variants showed remarkable declines in immune persistence, especially against the Omicron variant. The booster administration interval could be shortened to 3 months in endemic areas of the Omicron variant, whereas an appropriate prolonging of the booster administration interval did not affect the booster immunization effect.

Impact of salt substitute and stepwise reduction of salt supply on blood pressure in residents in senior residential facilities: Design and rationale of the DECIDE-Salt trial.

BACKGROUND: High sodium intake has been considered as the leading dietary risk factor for deaths and disability-adjusted life-years among older adults. High-quality randomized trials to evaluate the effects of practical sodium reduction strategies are needed. METHODS: The study is a cluster randomized trial with a 2 × 2 factorial design conducted in 48 senior residential facilities in northern China. These facilities are randomly assigned (1:1:1:1) to 1 of 4 groups: stepwise salt supply control (SSSC) in which 5%-10% of the study salt supply in the institutional kitchens will be reduced every 3 months, replacing normal salt with salt substitute (SS); SSSC only; SS only; or neither SSSC nor SS. The interventions last for 2 years with follow-up every 6 months. The primary outcome is the change in systolic blood pressure from baseline to 24 months. Secondary outcomes include the incidence of hyperkalemia, hyponatremia, cardiovascular events, and death. CURRENT STATUS: The study has recruited and randomized 48 senior residential facilities with 1,606 participants. Mean age at baseline was 71 years, and 76% are male. Both types of salt intervention were initiated in the study facilities between January and April 2018. CONCLUSION: The study is well placed to define the effects of 2 practical and scalable sodium reduction strategies for blood pressure reduction and will provide important new data about safety of these strategies among older adults in China.