The Novavax vaccine is 95% effective, but its effectiveness against the South African variant is halved.

Novavax Pharmaceuticals (Novavax) said Jan. 28 that the vaccine, which requires two doses, was 95.6 percent effective against the original coronavirus in a pivotal phase 3 clinical trial in the United Kingdom, but half as effective against the South African variant.

The Novavax vaccine trial in the U.K. covered 15,000 subjects between the ages of 18 and 84, 27 percent of whom, were older than 65, according to an AFP report from Washington.

The study showed that the vaccine provided 95.6 percent protection against the original coronavirus (Covid-19) and 85.6 percent against the British variant, but in a smaller trial of just over 4,400 people, the vaccine’s protection against the South African variant dropped to 49.4 percent.

Novavax said it had started work on a new vaccine for the new strain earlier this month and expected to select an ideal candidate in the next few days, followed by clinical trials in the second quarter.

Novavax’s new NVX-CoV2373 vaccine is one of six vaccine candidates in the U.S. government’s Operation Warp Speed vaccine research and development program, which has received $1.75 billion in funding and is also undergoing clinical trials in the United States and Mexico.

AFP reports that the mRNA vaccine, produced by Pfizer and Moderna, delivers the “ribonucleic acid messenger” (mRNA) of the new coronavirus spine protein to the body, producing an antiviral protein to protect the body. The Novavax vaccine, on the other hand, injects the protein of the virus into the body and stimulates the body to produce antibodies.