Novavax Presents COVID-19 Booster and Flu Combo Vaccine Studies

Pictured: Novavax logo behind a vaccine bottle/courtesy of STR/NurPhoto via Getty Images

At the World Vaccine Congress in Washington, D.C. on Wednesday, Maryland-based Novavax presented data on its COVID-19 booster and COVID-influenza combination vaccine candidate. Novavax shares rose 12% Thursday following the presentation. 

In one study, a booster dose of the company’s a protein nanoparticle vaccine, called Nuvaxovid (approved under emergency use authorization in the U.S.), elicited enhanced immune responses against newer variants of the SARS-CoV-2 virus, including Omicron BA.1, BA.4 and BA.5, in vaccinated individuals’ blood. The measured immune responses were comparable to three total doses of the approved messenger RNA (mRNA) vaccines. 

The purpose of the study was to compile “really relevant data as to where we are in the pandemic today, as opposed to two years ago,” Lisa Dunkle, vice president of clinical development and global medical lead at Novavax, told BioSpace.

The predominant COVID-19 strain circulating today is Omicron subvariant XBB.1.5, which currently accounts for 90% of new U.S. cases, according to the CDC.

Dunkle said that while existing vaccines and boosters have been effective against the earlier Omicron strains, XBB.1.5 is different.

“It’s got some very significant mutations in the receptor binding site, which makes it harder for the antibodies to neutralize the virus. It wasn’t until we got to XBB 1.5 that things began to fall apart, and unfortunately, it fell apart for all of the [currently marketed] vaccines.” Novavax's booster has not been tested against XBB.1.5.

The FDA is currently working to determine the recommended target strains for next-generation COVID-19 vaccines. Dunkle said she expects that decision by late May or early June.

While an updated vaccine would ideally target the variant that is circulating in the fall, that may not be realistic.

“I don’t think there’s any way to accurately get a vaccine that strain-specific . . . with the current variant that’s circulating, just given the current mutation rate of SARS-CoV-2,” Scott Roberts, assistant professor in infectious diseases and medical director, infection prevention at Yale, told BioSpace.

But, he added, existing bivalent boosters targeting both the original COVID-19 strain and Omicron BA.5 have generated neutralizing antibodies against XBB.1.5.

“The hope is that there’s enough cross-protection where the vaccine efficacy against severe disease, hospitalization and death going into the winter season is still there, and I’m optimistic that we’ll achieve that," he said. 

The Booster Debate

When boosters first began to roll out, a debate ensued over whether it was optimal to stick with the primary series vaccine for the booster shot (the homologous approach) or to switch to a vaccine from a different company (the heterologous approach).

In that vein, Novavax ran Study 307 measuring the immunogenic responses of people given a Novavax booster following a primary series of Pfizer’s Comirnaty, Moderna’s Spikevax, Nuvaxovid or the J&J vaccine, with and without a prior booster dose. While the study found that Novavax’s booster generated robust immunogenicity across the board, efficacy was highest in the homologous (all Novavax) cohort. 

While noting that this cohort was small, Dunkle said it did appear that antibodies were higher when Nuvaxovid was used as a homologous booster.

Novavax also tested the immunogenicity of people primed with three doses of an mRNA vaccine and boosted with either the original Novavax booster, its booster targeting BA.1 or its bivalent vaccine. The study found responses to be similar, regardless of the vaccine formulation.

Combination COVID-Flu Candidate

Also on Wednesday, Vivek Shinde, vice president of clinical development and lead for older adult influenza & RSV vaccines at Novavax, gave an update on the company’s COVID-influenza combination (CIC) candidate. The rationale outlined in Shinde’s presentation was quite simple: address two major health problems with one vaccine.

Roberts said he is on board with this approach.

“I think a combination vaccine is only going to hopefully boost compliance in those who intend to get both vaccines,” he said.  

For Roberts, a combination vaccine would need to first be effective against severe disease. His preferred secondary endpoints would be prevention against infection, prevention of transmission to others and in vitro data showing neutralizing antibodies.  

In a Phase I/II trial, Novavax is evaluating the safety and efficacy of various formulations for the CIC vaccine. Shinde’s presentation showed that adverse events were comparable to both Nuvaxovid and Novavax’s investigational flu vaccine, qNIV, on their own.

Shinde also reported that CIC formulations were immunogenic and induced strong functional antibody and CD4+ T cell responses against SARS-CoV-2 and multiple influenza strains.

Novavax will use these data to inform an ongoing Phase II dose confirmation study. Results from this study are expected in May or June 2023. 

Heather McKenzie is a senior editor at BioSpace, focusing on neuroscience, oncology and gene therapy. You can reach her at heather.mckenzie@biospace.com. Follow her on LinkedIn and Twitter @chicat08.