The main objective of this phase II trial is to evaluate the humoral immune response induced by the Ad26.COV2.S or NVX-CoV2373 vaccines in adults one month after complete vaccination regimen against SARS-CoV-2, compared younger (up to 45 years old) and elderly (55+ years old) populations.~400 participants will be included, 200 participants for each vacine. The age categories are 18 - 45 years, 55 - 64 years and 65+ years. The number of participants per age group will be distributed as follows 1:1:0,5. There will be no comparison between population on different vaccines.~Ad26.COV2 vaccine (200 participants) 18-45 years old, 80 participants 55-64 years old, 80 participants 65 years old or older, 40 participants~NVX-CoV2373 vaccine (200 participants) 18-45 years old, 80 participants 55-64 years old, 80 participants 65 years old or older, 40 participants~Participants in Ad26.COV2 arm receive intramuscularly as a single dose of 0.5mL.~Participants in NVX-CoV2373 arm receive 2 doses intramuscularly, the second dose 21 days apart, 0.5mL each.~Humoral vaccine immune responses, induced by Ad26.COV2.S and NVX-CoV2373 vaccines, will be measured by ELISA at D0, M1, M2, M6, M12 and M24.
Phase II, non-randomized, open-label, comparative, national, multicenter trial in Mali, aimed to assess the humoral vaccine immune response induced by Ad26.COV2.S and NVX-CoV2373 vaccines in 400 adults (200 participants for each vaccine), one month after receiving the complete vaccination schedule of SARS-CoV-2 vaccine.