Novavax COVID-19 Vaccine Demonstrates an Overall Efficacy of 90.4%

The biotechnology company Novavax has announced that its Phase III clinical trial of the COVID-19 vaccine NVX-CoV2373 demonstrated an overall efficacy of 90.4%.

The PREVENT-19 trial

The Phase III trial – known as PREVENT-19 – commenced in December 2020 and recruited 29,960 participants across 119 sites in the USA and Mexico. According to Novavax's statement, the trial emphasized "recruiting a representative population of communities and demographic groups most impacted by the disease".

The trial adopted a randomized, placebo-controlled and observer-blind methodology, meaning participants were allocated to receive either two doses of the NVX-CoV2373 vaccine or a placebo. Throughout the duration of the study, a total of 77 COVID-19 cases were observed: 63 in the placebo group and 14 in the group allocated to receive the NVX-CoV2373 vaccine. The primary endpoint for the PREVENT-19 trial was the first occurrence of a symptomatic, PCR-confirmed case of COVID-19 (mild, moderate or severe) at least seven days following the second dose. Consequently, the number of confirmed cases across the two groups yields an overall vaccine efficacy of 90.4%. Of the 63 confirmed cases in the placebo group, 10 were classified as moderate and 4 as severe. No moderate or severe cases were reported in the vaccinated group, translating to a vaccine efficacy of 100% against moderate/ severe disease.

"These clinical results reinforce that NVX-CoV2373 is extremely effective and offers complete protection against both moderate and severe COVID-19 infection," said Stanley C. Erck, president and chief executive officer at Novavax.

How effective is the vaccine against variants?

The study data was collected from January to April 2021, during which time several SARS-Cov-2 variants of interest (VoI) and concern (VoC) emerged, including the Alpha (formerly the "Kent") variant. Analyzing sequencing data from 54 of the 77 confirmed COVID-19 cases, the trial investigators found that 82% of the cases were VoC or VoI, and vaccine efficacy against these variants was therefore determined as 93.2%. 

Speaking to Technology Networks in 2020, Gregory Glenn, president of research and development at Novavax said, "Our particular vaccine technology is a full length, recombinant protein from the surface of the virus that is inserted into a nanoparticle and gives you an immune response to the conserved portion of the protein. It is therefore somewhat 'immune' to the effect of mutations. We already know there are mutations in SARS-CoV-2, but this should not impact the effectiveness of our vaccine."

What about safety?

According to Novavax, the PREVENT-19 trial data suggests the vaccine is generally well-tolerated; there were no single adverse events reported by more than one percent of the trial participants, and pain at the injection side were the most common symptoms reported, in addition to fatigue and headache. These symptoms have been observed across the various COVID-19 vaccines that have been tested and administered across the globe.

How is NVX-CoV2373 different to other COVID-19 vaccines?

NVX-CoV2373 is a recombinant nanoparticle protein-based COVID-19 vaccine , – also known as a "subunit vaccine" – which Dr Peter English, retired consultant in communicable disease control, described as more "traditional" compared to the mRNA and vector vaccines currently in distribution: “The actual [SARS-CoV-2] spike protein is injected, in the form of nanoparticles, instead of inserting the genetic material enabling our cells to create the spike protein," he said. "The more different types of vaccine we have, the greater our ability will be to optimize effectiveness and safety in different groups."

There are a number of hurdles to overcome when vaccinating the entire global population.  A key factor in the context of COVID-19 has been the storage requirements of "new-era" mRNA-based vaccines such as those developed by Moderna and Pfizer–BioNTech. mRNA-based vaccines contain genetic material (the mRNA) which requires colder temperatures than "traditional" subunit vaccines that contain proteins. Novavax states that NVX-CoV2373 is stable at refrigerated temperatures, which means it should integrate into the existing supply chains "without difficulty".

Could it therefore provide a solution to the ongoing issue of ensuring of vaccine access in poor countries where storage options are limited? Possibly. Writing in Science Translational Medicine, medicinal chemist Derek Lowe said , "By this point, the vaccine is much less needed here in the US, but it could be a very important part of getting many other countries vaccinated, due to its less demanding storage requirements and (relatively) straightforward production process."

When will the vaccine be authorized?

In May, Novavax announced that it had to delay filing for approval of NVX-CoV2373 with the US Food and Drug Administration, a decision that was attributed to manufacturing issues associated with process qualification and assay validations. However, in its most recent statement , the company confirmed that it remains on track to deliver 100 million doses each month by the end of Q3, increasing to 150 million doses per month by Q4 of this year.