Novavax COVID-19 Vaccine Booster Provides 6-Fold Delta Variant Antibodies

The report of promising phase 2 findings align with word that an FDA submission will be delayed until later this year.

A booster dose of Novavax’s investigative COVID-19 vaccine NVX-CoV2373 is associated with a 4.6-fold increase in functional antibody titers against the pandemic virus, according to a press release shared by the biotechnology company Thursday.

New data from an ongoing phase 2 trial in the US and Australia assessing the 2-dose recombinant nanoparticle protein-based COVID-19 vaccine showed that a 6-month booster dose in observed participants significantly improved antibody titers while providing hope of benefit versus the highly transmissible B.1.617.2 (delta) SARS-CoV-2 variant.

The booster dose-supported vaccine regimen provided 6 times greater functional ACE-2 binding inhibition antibodies that are cross-reactive with the surging variant than that observed in the primary 2-dose vaccination series, according to Novavax.

Promising Phase 2 Findings

The trial, from which data will be submitted to a peer-reviewed publication and be made available on preprint servers, has been observing a 5 mcg dose cohort who received a 5 mcg booster 189 days following the second shot of the generally 2-dose regimen.

The phase 2 findings come at a time of discussion surrounding breakthrough infection risk in vaccinated persons due to more transmissible SAS-CoV-2 variants—as well as consideration of regulated booster vaccine doses from already-authorized developers such as Pfizer-BioNTech.

Investigators additionally observed good tolerance associated with the Novavax booster dose; 90% of symptoms were rated as mild or moderate following the third dose in vaccinated participants.

In a statement accompanying the release, Gregory M. Glenn, MD, President of Novavax Research and Development, called the results a reinforcement of confidence in the potential of a NVX-CoV2373 booster dose in providing “broad protection against disease.”

"Given the evidence that natural and vaccine-induced immunity wanes over time, the continuation of our proactive clinical development program will be critical to understanding and demonstrating the effectiveness of our recombinant nanoparticle COVID-19 vaccine,” Glenn said.

Delayed Submission

Though the findings may indicate continued promise for a fourth US Food and Drug Administration (FDA)-regulated COVID-19 vaccine, NVX-CoV2373 will likely be unavailable for use in the US until at least the end of the year.

Novavax announced on Thursday a delay of Emergency Use Authorization (EUA) submission to the FDA until the fourth quarter of 2021, after filing for regulatory approval in India, Indonesia, and the Philippines. The company will submit the vaccine for emergency use listing by the World Health Organization (WHO) this month.

As of Thursday, the US is reporting a 7-day average of 96,000-plus new COVID-19 cases. More than 1600 Americans have died from complications associated with COVID-19 in the first 4 days of August.