LB-9 - Development of a SARS-CoV2 vaccine, ChAdOx1 nCoV19: immunogenicity and safety in older adults

Background: The pandemic of SARS-CoV2 has led to a huge impact on population health, resilience of health systems and economies. While social distancing measures have been shown to slow spread, the end of the pandemic will only be achieved with sufficient population immunity in those at greatest risk, and this is most safely achieved through vaccination. We tested safety and immunogenicity of a novel viral vector vaccine in older age groups to consider the potential impact in older adults

Methods: Healthy adults were recruited aged 18-55, 56-69 and ≥70 years and enrolled in the phase II clinical to receive 1 or 2 doses of either ChAdOx1-nCoV19 (AZD1222) or a control vaccine (MenACWY). Safety was monitored using a diary to collect local and systemic solicited symptoms. Blood was drawn at baseline and 14 and 28 days after primary and booster vaccination. Immune responses were evaluated by ELISA, in a neutralizing assay and by interferon-gamma ELISPOT.
 
 

Results: Immune responses were demonstrated across all ages, with stronger antibody responses after a second dose of vaccine administered 1 month after the first. Local and systemic reactogenicity was lower at older ages than in younger adults and lower after the second dose then after the first.

Conclusion: ChAdOx1-nCoV19 has an acceptable tolerability profile and is immunogenic in adults above 18 years of age including older adults, with stronger responses after a second dose. Phase III clinical trials for further evaluation are ongoing.