Shot effective against original strain, Beta, Gamma variants The shot neutralized the Delta variant within 29 days of administering the single dose and protection improved over time, the company said. Further, the vaccine is also highly effective against the original coronavirus strain, the Beta, Gamma, Alpha, and Kappa variants, the statement added. "Johnson & Johnson's single-dose COVID-19 vaccine was 85 percent effective against severe/critical disease and demonstrated protection against hospitalization and death." Studies Results will be published in online depository bioRxiv These results were from two studies, J&J said. The company tested the blood samples of eight participants in its late-stage trial to assess neutralizing antibodies against Delta and other variants.