COVID-19 vaccine shows promise against UK’s new variant

Novavax, Inc. has announced that NVX-CoV2373, its protein-based COVID-19 vaccine candidate, had a vaccine efficacy of 89.3 percent in its Phase III clinical trial conducted in the UK. The interim analysis suggests the vaccine is effective against the new variant strain of the virus, B.1.1.7, which was first detected in the UK. The company also announced successful results from its Phase IIb study conducted in South Africa.

“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,” commented Stanley Erck, President and Chief Executive Officer of Novavax. “NVX-CoV2373 has the potential to play an important role in solving this global public health crisis. 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.”

NVX-CoV2373 contains a full-length, prefusion Spike (S) protein made using Novavax’ 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 S protein and is produced in insect cells. It can neither cause COVID-19 nor replicate, is stable at refrigerated temperatures (2-8°C) and shipped in a ready-to-use liquid formulation that permits distribution using existing vaccine supply chain channels.

UK results: 89.3 percent vaccine efficacy

The UK study enrolled more than 15,000 participants between 18 and 84 years of age, including 27 percent over the age of 65. The primary endpoint of the trial is based on the first occurrence of PCR-confirmed symptomatic COVID-19 with onset at least seven days after the second study vaccination in participants that were serologically negative 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 in the NVX-CoV2373 group, representing an estimated vaccine efficacy of 89.3 percent. Of the 62 cases, 61 were mild or moderate and one was severe (in placebo group).

A preliminary analysis also indicates that the vaccine is effective against the B.1.1.7, with a vaccine efficacy of 95.6 percent against the original COVID-19 strain and 85.6 percent against the new UK variant.

The interim analysis included a preliminary review of the safety database, which showed that severe, serious and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups.

Novavax said it expects to share further trial results as additional data become available.

Phase IIb results: over 90 percent of COVID-19 cases caused by South African escape variant

In the Phase IIb trial, NVX-CoV2373 had a 60 percent efficacy for preventing COVID-19 in HIV-negative participants (94 percent of the study population). The study met its primary endpoint, with an efficacy of 49.4 percent in the overall trial population, including HIV-positive and HIV-negative subjects.

The trial enrolled over 4,400 patients beginning in August 2020, with COVID-19 cases counted from September through mid-January. During this time, the triple mutant variant (B.1.351) was widely circulating in South Africa. Preliminary sequencing data for 27 of 44 COVID-19 events shows that 92.6 percent (25 out of 27 cases) were caused by the South Africa escape variant.

According to the company, one of the important aspects of this trial was that approximately a third of participants were seropositive, ie, had had a prior COVID-19 infection, at baseline. 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.

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.