US begins final tests of coronavirus vaccine candidate

Phase-three trials began on Monday of a candidate vaccine against the novel coronavirus in the US, with an expected enrolment of 30,000 volunteers, the National Institutes of Health announced.

The vaccine was co-developed by biotechnology company Moderna, Inc., based in Cambridge, Massachusetts, and the National Institute of Allergy and Infectious Diseases (NIAID).

The trial will be conducted at 89 US clinical research sites with adult volunteers who do not have Covid-19, according to the statement.

NIAID Director Anthony Fauci said results from earlier clinical testing indicated that the vaccine was "safe and immunogenic, supporting the initiation of Phase 3 clinical trial."

"This scientifically rigorous, randomised, placebo-controlled trial is designed to determine if the vaccine can prevent Covid-19 and for how long such protection may last."

The vaccine efficacy trial is the first to be implemented under Operation Warp Speed, a governmental program that aims to begin delivering millions of doses of an effective virus vaccine by the end of 2020.

The trial is designed to determine if the vaccine can prevent symptomatic Covid-19 after two doses and it aims to study whether the vaccine can prevent severe infection with or without disease symptoms, the NIH said.

It also seeks to answer whether the vaccine can prevent death caused by the virus and if just one dose can prevent symptomatic Covid-19, among other objectives.

Trial volunteers will receive two injections approximately 28 days apart and some participants will be assigned at random to a control group that will be administered placebo doses.

"The launch of this Phase 3 trial in record time while maintaining the most stringent safety measures demonstrates American ingenuity at its best and what can be done when stakeholders come together with unassailable objectivity toward a common goal," NIH Director Francis Collins said.

Investigators will use public health data and incidence trajectory modelling to identify sustained high-incidence areas and emerging hot zones, so sites near these locations can be prioritised for enrolment.

The US government also backs the vaccine research of the Maryland-based Novavax biotechnology firm and Pfizer pharmaceutical corporation in New York City.

The US is the worst-hit country by the pandemic with more than 4.2 million cases and nearly 147,000 deaths, according to a running tally of Johns Hopkins University. In all, nearly 1.3 million recoveries have been recorded.

Many parts of the country have recently suffered new surges in virus cases.