Novavax COVID-19 vaccine demonstrates 89.3% efficacy
Biotechnology company Novavax has announced that NVX-CoV2373, its protein-based COVID-19 vaccine candidate, has demonstrated a vaccine efficacy of 89.3% in a Phase 3 clinical trial conducted in the UK, meeting the primary endpoint of the trial. The company also announced promising results of its Phase 2b study conducted in South Africa.
NVX-CoV2373 contains a full-length, prefusion spike protein made using Novavax’s recombinant nanoparticle technology and the company’s proprietary saponin-based Matrix-M adjuvant. The purified protein is encoded by the genetic sequence of the SARS-CoV-2 spike (S) protein and is produced in insect cells. It can neither cause COVID-19 nor can it replicate, is stable at 2 to 8°C (refrigerated) and is shipped in a ready-to-use liquid formulation that permits distribution using existing vaccine supply chain channels.
The UK study assessed efficacy during a period with high transmission and with a new UK variant strain of the virus emerging and circulating widely. It enrolled more than 15,000 participants between 18 and 84 years of age, including 27% over the age of 65. The primary endpoint was based on the first occurrence of PCR-confirmed symptomatic (mild, moderate or severe) COVID-19 with onset at least seven days after the second study vaccination in serologically negative (to SARS-CoV-2) adult participants at baseline.
The first interim analysis is based on 62 cases, of which 56 cases of COVID-19 were observed in the placebo group versus six cases observed in the NVX-CoV2373 group, resulting in a point estimate of vaccine efficacy of 89.3%. Of the 62 cases, 61 were mild or moderate and one was severe (in the placebo group). Severe, serious and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups.
Preliminary analysis indicates that the UK variant strain was detected in over 50% of the PCR-confirmed symptomatic cases (32 UK variant, 24 non-variant, six unknown). Based on PCR performed on strains from 56 of the 62 cases, efficacy by strain was calculated to be 95.6% against the original COVID-19 strain and 85.6% against the UK variant strain (post hoc).
“These are spectacular results, and we are very pleased to have helped Novavax with the development of this vaccine,” said Clive Dix, Chair of the UK Vaccine Taskforce. “The efficacy shown against the emerging variants is also extremely encouraging. This is an incredible achievement that will ensure we can protect individuals in the UK and the rest of the world from this virus.”
South African results
The South Africa Phase 2b clinical trial enrolled over 4400 patients beginning in August 2020, with COVID-19 cases counted from September through mid-January. During this time, the triple mutant variant, which contains three critical mutations in the receptor binding domain (RBD) and multiple mutations outside the RBD, was widely circulating in South Africa. Preliminary sequencing data is available for 27 of 44 COVID-19 events; of these, 92.6% were the South Africa escape variant.
The trial demonstrated 60% efficacy for the prevention of mild, moderate and severe COVID-19 disease in the 94% of the study population that was HIV-negative. 29 cases were observed in the placebo group and 15 in the vaccine group. One severe case occurred in the placebo group and all other cases were mild or moderate. When covering the overall trial population of both HIV-positive and HIV-negative subjects, efficacy was 49.4%.
Approximately one-third of the patients enrolled were seropositive, demonstrating prior COVID-19 infection at baseline. Based on temporal epidemiology data in the region, the pre-trial infections are thought to have been caused by the original COVID-19 strain, while the subsequent infections during the study were largely variant virus. These data suggest that prior infection with COVID-19 may not completely protect against subsequent infection by the South Africa escape variant; however, vaccination with NVX-CoV2373 provided significant protection.
“This is the first COVID-19 vaccine for which we now have objective evidence that it protects against the variant dominating in South Africa,” said Professor Shabir Maddi, Executive Director of the Vaccines and Infectious Diseases Analytics Research Unit (VIDA) at Wits University and principal investigator for Novavax’s South African vaccine trial. “I am encouraged to see that Novavax plans to immediately begin clinical development on a vaccine specifically targeted to the variant, which together with the current vaccine is likely to form the cornerstone of the fight against COVID-19.”
Novavax initiated development of new constructs against the emerging strains in early January and expects to select ideal candidates for a booster and/or combination bivalent vaccine for the new strains in the coming days. The company plans to initiate clinical testing of these new vaccines in the second quarter of this year.
“A primary benefit of our adjuvanted platform is that it uses a very small amount of antigen, enabling the rapid creation and large-scale production of combination vaccine candidates that could potentially address multiple circulating strains of COVID-19,” said Dr Gregory M Glenn, President of Research and Development at Novavax. “Combined with the safety profile that has been observed in our studies to date with our COVID-19 vaccine, as well as prior studies in influenza, we are optimistic about our ability to rapidly adapt to evolving conditions.”
Stanley C Erck, President and CEO of Novavax, concluded, “NVX-CoV2373 is the first vaccine to demonstrate not only high clinical efficacy against COVID-19, but also significant clinical efficacy against both the rapidly emerging UK and South Africa variants.
“We look forward to continuing to work with our partners, collaborators, investigators and regulators around the world to make the vaccine available as quickly as possible.”
The Australian Government has agreed to purchase 40 million doses of the Novavax vaccine, subject to approval from the Therapeutic Goods Administration (TGA).
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