An article in the Journal of Infection indicates that the Antibody Dependent Enhancement scenario is in effect courtesy of the Delta variant.
Current Covid-19 vaccines (either mRNA or viral vectors) are based on the original Wuhan spike sequence. Inasmuch as neutralizing antibodies overwhelm facilitating antibodies, ADE is not a concern. However, the emergence of SARS-CoV-2 variants may tip the scales in favor of infection enhancement. Our structural and modeling data suggest that it might be indeed the case for Delta variants.
In conclusion, 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. However, although the results obtained so far have been rather reassuring, to the best of our knowledge ADE of Delta variants has not been specifically assessed. Since our data indicate that Delta variants are especially well-recognized by infection enhancing antibodies targeting the NTD, the possibility of ADE should be further investigated as it may represent a potential risk for mass vaccination during the current Delta variant pandemic.
Infection-enhancing anti-SARS-CoV-2 antibodies recognize both the original Wuhan/D614G strain and Delta variants. A potential risk for mass vaccination? August 16, 2021
However, the reader who sent me the study notes: This got through peer review. Case Nighmare Kitty highly unlikely. Delta is not that lethal.
And that’s pretty much what we’re seeing in the international data. Although most of the deaths are of the vaccinated, indicating ADE, there just aren’t very many of them due to the lower lethality of the Delta variant.