New York,  Novavax's Covid-19 vaccine is 90 per cent effective at preventing Covid-19 illness, according to results from a Phase 3 clinical trial.

In addition to being highly effective in preventing Covid illness of any severity, the vaccine was 100 per cent effective in preventing moderate and severe disease that required hospitalisation, revealed the study published in the New England Journal of Medicine.

For the trial, the team from University of Maryland included nearly 30,000 adult volunteers at 113 clinical sites in the US and six sites in Mexico.

Approximately 20,000 participants received two doses of the vaccine spaced three weeks apart and 10,000 received placebos. The trial was conducted during the first few months of 2021, and tested only against Alpha variant, which was the predominant circulating strain.

Most side effects were mild to moderate and transient. Fever was very rare. The most common side effects in the vaccine recipients included pain and tenderness at the injection site, headache, muscle aches and fatigue that lasted a day on average. None of the recipients developed serious reactions like heart inflammation (myocarditis) or blood clots.

"Our study results indicate that this vaccine is highly efficacious and very safe. In addition, this vaccine has many attractive features," said Karen Kotloff, Professor of Paediatrics at the varsity's School of Medicine.

"It is made from a small piece of protein, like many currently licensed vaccines in the US and has convenient refrigerator storage requirements, so it will be an important addition to the Covid-19 vaccine portfolio, in the US and in countries where supply is lacking," Kotloff added.

Novavax is also a partner of Pune-based Serum Institute of India. The vaccine NVX-CoV2373 is already being locally manufactured by the company under the brand name Covovax - its vaccine for children aged above 3 years. It will be launched in the next six months, SII CEO Adar Poonawalla has said.

Covavax is currently under trial and has shown excellent results down to the age of 3 years, Poonawalla said.