US biotech firm Inovio on Tuesday reported encouraging results in preliminary clinical trials for its Covid-19 vaccine candidate.

The firm had administered the vaccine on 40 volunteers. According to the results, the vaccine candidate had triggered an immune system response in 94 per cent of the volunteers who had completed the phase one trial. The volunteers were given two shots four weeks apart, AFP reported.

Inovio's vaccine candidate, INO-4800, is designed to generate an immune response system against the novel coronavirus by injecting DNA into a person.

Innovio is one of the firms that is part of the United States President Donald Trump’s project Warp Speed. The project is meant to speed up the development of a Covid-19 vaccine and aims to deliver 300 million doses of a vaccine for Covid-19 by January 2021.

The United States has so far approved four coronavirus vaccine candidates for clinical trials, the US Food and Drug Administration (FDA) head Stephen Hahn said as per reports.

Six additional vaccine candidates are in the pipeline, Hahn added. The USFDA on Tuesday also released detailed guidelines for approval of Covid-19 vaccine candidates.

According to the guidelines, the vaccine will have to be at least 50 per cent more effective than a placebo in terms of preventing Covid-19 infection. The USFDA will also direct vaccine manufacturers to monitor volunteers after any approval for a year as “post-market studies” might be necessary to “further assess known or potential serious risks.”

Currently, US firm Moderna’s experimental vaccine candidate is one of the front-runners in the vaccine race.

The US has reported over 2.6 million cases of Covid-19 so far with fatalities surpassing 1.2 lakh.