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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 modelling 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 vaccines6, 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 reassuring1, 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. In this respect, second generation vaccines7 with spike protein formulations lacking structurally-conserved ADE-related epitopes should be considered.

https://www.journalofinfection.com/article/S0163-4453(21)00392-3/fulltext