An experimental coronavirus vaccine from the biotechnology company Novavax was 90% effective at preventing COVID-19 in a large clinical trial run in the U.S. and Mexico, a crucially important result that could add another protective shot to the world's arsenal.
Results from the Phase 3 study also showed that two doses of Novavax's vaccine were strongly protective against several coronavirus variants being closely monitored by global health authorities, the company said Monday. There were few or no cases reported in the trial of some of the most worrying strains, however.
Data from the trial, which enrolled nearly 30,000 volunteers, have been highly anticipated for weeks and position Novavax to soon ask regulators for authorization of its vaccine. The company intends to submit applications in the third quarter, once it completes the "final phases" of work to validate its manufacturing process and tests.
"Novavax continues to work with a sense of urgency to complete our regulatory submissions and deliver this vaccine, built on a well understood and proven platform, to a world that is still in great need of vaccines," said company CEO Stanley Erck in a statement Monday.
In the U.S., U.K., Canada and Europe, Novavax began filing some materials with regulators on a rolling basis in early February.
Notably, vaccination in the Phase 3 trial was associated with relatively modest rates of side effects, although Novavax gave only summary details in its announcement of the data. Injection site pain, fatigue, headache and muscle pain were the most common side effects experienced by study participants, and very few were classified as severe.
Serious and severe adverse events "were low in number and balanced between vaccine and placebo groups," Novavax said.
While comparing across clinical trials is difficult, the rates of some side effects appear less than those associated with the vaccines developed by Pfizer and BioNTech as well as Moderna.
The results largely confirm earlier findings from a smaller Phase 3 trial run in the U.K., which in late January had shown 89% efficacy among some 15,000 participants.
Unlike other, already authorized vaccines for COVID-19, which rely on genetic material or inactivated virus, Novavax's shot is constructed from the coronavirus' characteristic spike protein and paired with an immune-boosting substance known as an adjuvant. It's a technology that's well established, easy to store and familiar to many vaccine manufacturers, potentially aiding future global supply.
But Novavax has hit delays, both in completing its trial and in scaling up its own production. The company, which has built a sprawling network of suppliers, partners and vaccine factories around the world, expects to be able to make 100 million doses per month by the end of September, and 150 million doses per month by December.
The shot is important to COVAX, a program set up the World Health Organization and nonprofits to procure and distribute vaccines around the world. In May, Novavax agreed to supply GAVI, a COVAX partner, with 350 million doses of its shot, making the biotech one of the program's largest suppliers.
A separate deal with the Serum Institute of India could supply hundreds of millions of doses more, although India's ongoing COVID-19 crisis has led the government to shut down vaccine exports.
Through the Trump administration's Operation Warp Speed, the U.S. preordered 100 million doses of Novavax's vaccine in a deal that gave Novavax $1.6 billion to help develop and manufacture the shot.
But the U.S. may not need many of those doses. More than half of the U.S. population has received at least one dose of the available vaccines from Pfizer, Moderna and J&J. Counting only people above the age of 12, that figure is 62% and rising. Supplies of Pfizer's and Moderna's are now abundant and vaccination rates are slowing.
Novavax, which is based in Maryland, has tried unsuccessfully for decades to develop vaccines for various infectious diseases, including SARS, Middle East respiratory syndrome and Ebola. Before the company's pivot to COVID-19 brought fresh funding and attention, its finances and future looked shaky.
The results announced Monday are validation for the company's science and persistence, particularly after other, more successful vaccine makers like Sanofi and Merck & Co. have faltered or given up.
Many details aren't yet available; Novavax plans to submit the data to peer-reviewed journals for publication. But the summary results announced by press release appear strong, comparing well against the high bar set last November and December by Pfizer and Moderna.
Overall, the efficacy of two doses of Novavax's vaccine, given 21 days apart, was measured as 90.4% in the Phase 3 trial, which randomized participants at a 2:1 ratio to receive either vaccine or placebo. Seventy-seven cases of COVID-19 were reported, 63 of which occurred among volunteers who received placebo and 14 among those who were vaccinated.
All 14 cases among vaccinated volunteers were classified as mild. By comparison, 10 of the 63 cases in the placebo arm were moderate, and four were severe.
The trial's main phase ran from December through the end of April, a period in which several coronavirus variants became much more prevalent in the U.S., where nearly all of the study sites were located. Researchers were able to sequence 54 of the 77 cases and determined 35 were infections by a "variant of concern," mostly one first identified in the U.K. that's now called Alpha. Nine cases were infections by a "variant of interest," which describes variants that researchers are monitoring but haven't yet confirmed transmit more easily or are more lethal.
Measured against those variants, vaccine efficacy was 93.2%, Novavax said.
There were only two cases, however, linked to a variant that was originally detected in South Africa and is known to weaken vaccine potency. An earlier, smaller study of Novavax's vaccine in South Africa found a much lower efficacy of about 50%. There were also no sequenced cases associated with the "Delta" variant that was first found in India and is viewed as a risk to spread widely in the U.S. and elsewhere.
Like Pfizer and Moderna, Novavax is studying whether booster shots could improve protection versus variants, although its work is in early stages.
Only 13% of participants in the trial were older than 65, a demographic that's at much higher risk of worse health outcomes from COVID-19 and who were given preferential access to the first supplies of Pfizer's and Moderna's vaccines in the U.S.
Among high-risk individuals, including older adults as well as those under 65 with pre-existing conditions, vaccine efficacy was 91%, Novavax said. The company's announcement did not specifically break out efficacy by age.
Twenty percent of participants identified as Latin American, 12% as African American, 7% as Native American and 5% as Asian American.
Novavax is continuing to study its vaccine in a cohort of about 2,250 trial participants aged between 12 and 18 years. Pfizer's vaccine is authorized for teenagers in that age range, while Moderna recently asked the FDA to extend its shots' clearance to include adolescents over 12 as well. Both are testing their vaccines in younger kids, too.
Note: This story has been updated with additional detail throughout.