(CNN)There is some good news on Johnson & Johnson's coronavirus vaccine.
Early results from a Phase 1/2a clinical trial show it was well tolerated and even one dose appeared to produce a strong immune response in almost all of the 800 participants.
The trial included two age groups: 18- to 55-year-olds and 65 and older, and looked at the safety and side effects of two different doses. Initial findings from the trials suggest the vaccine does provoke an immune response and is safe enough to move into large-scale trials.
The study was posted on MedRxiv, but it has not been peer-reviewed or published in a medical journal yet.
The researchers found that 99% of the participants age 18 to 55 in both dose groups had developed antibodies against the virus 29 days after getting vaccinated. The analysis found that most of the side effects, like fever, headache, fatigue, body aches and injection-site pain, were mild and resolved after a couple of days.
Some of the participants will be receiving a second shot of the vaccine as part of the trial.
The vaccine -- called Ad26.COV2.S -- uses the same technology used for Johnson & Johnson's Ebola, Zika, HIV and RSV vaccines.
Phase 3 trials will examine the safety and effectiveness of a single dose against a placebo to prevent symptomatic Covid-19. Johnson & Johnson says it plans to enroll 60,000 adult volunteers at more than 200 sites in the US and internationally.
The fact that the trial will examine the efficacy of a single dose of the vaccine, instead of two doses, should expedite results, according to Dr. Paul Stoffels, Johnson & Johnson's chief scientific officer.
So far, it's the only Phase 3 Covid-19 vaccine trial in the United States that is testing a single-dose of the vaccine.
The company says stricter vaccine guidelines under consideration by the US Food and Drug Administration might add to the company's vaccine timeline.
Fauci's take on vaccines
Meanwhile, Dr. Anthony Fauci, National Institute of Allergy and Infectious Diseases director, says Covid-19 vaccinations could very likely start in November or December.
But he warns it may be late 2021 before things are back to normal.
"By the time you get enough people vaccinated so that you can feel you've had an impact enough on the outbreak, so that you can start thinking about maybe getting a little bit more towards normality, that very likely, as I and others have said, will be maybe the third quarter or so of 2021. Maybe even into the fourth quarter," he said in an online conversation with Dr. Howard Bauchner, editor-in-chief of the Journal of the American Medical Association.
But he added it is unlikely that political interference will play a role in the approval process of a Covid-19 vaccine.
"If you look at the standard process of how these things work, I think you could feel comfortable that it is really unlikely that that's going to happen," Fauci said.