A coronavirus vaccine developed by the German Centre for Infection Research (DZIF) and vaccine maker IDT Biologika did not prompt the hoped-for immune reaction in early-stage testing on humans, trial organizers at university hospital Hamburg-Eppendorf (UKE) said on Friday.

Further testing has been suspended until the cause for the weak immunogenicity in the Hamburg trial involving 30 volunteers has been established, UKE said in a statement, adding that the vaccine was well tolerated.

IDT said in November it was hoping to be able to apply for regulatory approval at the end of 2021.