Waning Effectiveness of SARS-CoV-2 mRNA Vaccines in Older Adults: A Rapid Review

The U.S. Centers for Disease Control and Prevention (CDC) and other health agencies have recently recommended a booster dose of COVID-19 vaccines for specific vulnerable groups including adults 65 years and older. There is limited evidence whether vaccine effectiveness in older adults decreases over time, especially against severe COVID-19. We performed a rapid review of published studies available through 04 November 2021 that provide effectiveness data on mRNA vaccines approved/licensed in the United States and identified eight eligible studies which evaluated vaccine effectiveness in older adults. There is evidence of a decline in vaccine effectiveness against both SARS-CoV-2 infection and severe COVID-19 in older adults among studies which analyzed data up to July-October 2021. Our findings suggest that vaccine effectiveness diminishes in older adults, which supports the current recommendation for a booster dose in this population.

An adjuvanted SARS-CoV-2 RBD nanoparticle elicits neutralizing antibodies and fully protective immunity in aged mice

Development of affordable and effective vaccines that can also protect vulnerable populations such as the elderly from COVID-19-related morbidity and mortality is a public health priority. Here we took a systematic and iterative approach by testing several SARS-CoV-2 protein antigens and adjuvants to identify a combination that elicits neutralizing antibodies and protection in young and aged mice. In particular, SARS-CoV-2 receptorbinding domain (RBD) displayed as a protein nanoparticle (RBD-NP) was a highly effective antigen, and when formulated with an oil-in-water emulsion containing Carbohydrate fatty acid MonoSulphate derivative (CMS) induced the highest levels of cross-neutralizing antibodies compared to other oil-in-water emulsions or AS01B. Mechanistically, CMS induced antigen retention in the draining lymph node (dLN) and expression of cytokines, chemokines and type I interferon-stimulated genes at both injection site and dLN. Overall, CMS:RBD-NP is effective across multiple age groups and is an exemplar of a SARS-CoV-2 subunit vaccine tailored to the elderly.