According to Sputnik news  - US corporation Johnson & Johnson has started its Phase 3 trials of a possible single-shot  COVID-19 vaccine, the company said in a press release on Wednesday.

“Johnson & Johnson (NYSE: JNJ) (the Company) today announced the launch of its large-scale, pivotal, multi-country Phase 3 trial (ENSEMBLE) for its COVID-19 vaccine candidate, JNJ-78436735, being developed by its Janssen Pharmaceutical Companies,” the release said.

The final stage of the study will be conducted on 60,000 adult volunteers in the United States, Argentina, Brazil, Chile, Colombia, Mexico, Peru and South Africa, the release said.

The Johnson & Johnson single-dose shot is the fourth vaccine candidate to enter late-stage testing in the United States, after Moderna, Pfizer/BioNTech and AstraZeneca. began similar trials. The other vaccine candidates require two doses.

The company plans to include in its study members of populations that have been disproportionately affected by the COVID-19, including Black, Hispanic, American Indian and Alaskan Native volunteers, the company said.

According to WHO protocols, a candidate vaccine has to complete three phases of clinical trials to be approved for industrial production.

Phase 1 normally involves small-scale studies on up to 100 participants to determine a candidate vaccine's safety and clinical tolerance. Phase 2 can include up to 1,000 and is more representative in terms their age, ethnicity and other statistically significant factors. This phase pursues to determine the optimal dose, intervals between doses and the minimum necessary number of doses in a target population.

Phase 3 trials are the largest and can include up to 10,000 participants with the maximum representation of target population categories. A candidate vaccine is ready to move into industrial production if this last phase provides clear and definitive evidence of its safety and efficacy.