“Infection-enhancing antibodies have been detected in symptomatic Covid-19. Antibody dependent enhancement (ADE) is a potential concern for vaccines.”
“…in the case of the Delta variant, neutralizing antibodies have a decreased affinity for the spike protein, whereas facilitating antibodies display a strikingly increased affinity. Thus, ADE may be a concern for people receiving vaccines based on the original Wuhan strain spike sequence…”
“ADE may occur in people receiving vaccines based on the original Wuhan strain spike sequence (either mRNA or viral vectors) and then exposed to a Delta variant. Although this potential risk has been cleverly anticipated before the massive use of Covid-19 vaccines, the ability of SARS-CoV-2 antibodies to mediate infection enhancement in vivo has never been formally demonstrated.”
Source: Journal of Infection