New York, Sep 26 (IANS): A leading Covid-19 vaccine candidate developed by global healthcare company Johnson & Johnson produced a strong immune response against novel coronavirus in early-to-mid stage clinical trials, a report said.

According to the CNN, early results from a Phase 1/2a clinical trial show that 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: 18-55 and 65 and above and looked at the safety and side-effects of two different doses.

Initial findings from the trials suggest that the vaccine does provoke an immune response and is safe enough to move into large-scale trials.

During the study, the researchers found that 99 per cent of the participants (age 18-55) in both dose groups developed antibodies against the virus 29 days after getting vaccinated.

The analysis found that most of the side-effects, like fever, headache, fatigue, body ache and injection-site pain, were mild and got resolved after a couple of days.

Some of the participants will be receiving a second shot of the vaccine as part of the trials. The vaccine -- called Ad26.COV2.S -- uses the same technology used for Johnson & Johnson's Ebola, Zika, HIV and RSV vaccines.

According to the report, Phase 3 trials will examine the safety and effectiveness of a single dose against a placebo to prevent symptomatic Covid-19.

Johnson & Johnson said it plans to enrol 60,000 adult volunteers at more than 200 sites in the US and internationally.

"The fact that the trials will examine the efficacy of a single dose of the vaccine, instead of two doses, should expedite results," Paul Stoffels, Johnson & Johnson's chief scientific officer, was quoted as saying by the CNN.

So far, it's the only Phase 3 Covid-19 vaccine trial in the US that is testing a single-dose of the vaccine.