Johnson & Johnsonâs COVID-19 vaccine shows promising response in early trial after one dose Johnson & Johnson and last updated 2021-01-14 12:20:55-05 Results from early stage trials of Johnson & Johnsonâs COVID-19 vaccine are promising, showing the one-dose vaccine generates an immune response in nearly all volunteers, with minimal side effects. The company plans to release more details in a few weeks, and apply for emergency use authorization from the FDA in February. Researchers say Phase 1-2 of the vaccine showed either one or two doses of the vaccine generated both antibody and T-cell responses against the coronavirus. The vaccineâs efficacy, how well it protects against a COVID-19 infection or symptoms, is being tested in Phase 3 trials happening now.