Johnson & Johnson’s (J&J) single-dose vaccine is far less effective against the Delta and Lambda strains of the SARS‑CoV‑2 virus than against the original coronavirus, researchers at New York University (NYU) reported.

In laboratory testing, J&J’s adenovirus-based vaccine showed only low neutralizing antibody activity against variants, while the messenger RNA-based vaccines from Pfizer/BioNTech and Moderna displayed modest activity, the NYU research team said.

The research suggests that a second vaccine dose may be necessary for those vaccinated with the single-dose J&J shot, the NYU researchers said.