Novavax’s Updated COVID-19 Vaccine's Continue to Enhance Immune Response
The latest Phase 2/3 trial results show NVX-CoV2601 outperforms its predecessor, offering protection against emerging COVID-19 strains.
Interim results from a Phase 2/3 study of the Novavax COVID-19 vaccine, NVX-CoV2601, demonstrate significant improvements in immune response, suggesting its potential as an effective booster for adults in the U.S. The study, which was conducted between September 2023 and January 2024, showed that NVX-CoV2601, based on a recombinant spike protein from the Omicron XBB.1.5 variant, induced higher neutralizing antibody responses compared to the original NVX-CoV2373 vaccine.
Robert Walker, MD, Novavax's chief medical officer, discussed the importance of vaccine updates, “Currently, it’s about once a year that the vaccines are updated, similar to how influenza vaccines work.” He explained that the original NVX-CoV2373 vaccine was based on the first strain of COVID-19, while the updated NVX-CoV2601 was designed to target the Omicron XBB.1.5 variant that was circulating during the study. “Both vaccines should be classified the same—they are both COVID-19 vaccines. One is based on the original, more ‘prototype’ strain, while the other reflects the newer circulating strain at the time of the study,” Walker said.
The study showed that NVX-CoV2601 produced a geometric mean neutralizing antibody (nAb) titer of 905.9 at day 28, compared to 156.6 for NVX-CoV2373. The geometric mean titer ratio (GMTR) between the two groups was 5.8, indicating that the new vaccine generated significantly higher levels of neutralizing antibodies. Additionally, 64% of participants in the NVX-CoV2601 group showed a seroresponse, compared to just 7% in the NVX-CoV2373 group. These results suggest that the updated vaccine can generate a stronger immune response, which Walker believes is likely to translate into better protection against COVID-19.
“Not surprisingly, when we vaccinated with the new strain, we observed a superior immune response. This improved immune response is very likely to translate into better protection,” said Walker, emphasizing the value of updating the vaccine to match the circulating strain. He further noted that this strategy is crucial for addressing the evolving nature of COVID-19. “It is indeed valuable to update the vaccine strain to match the strain circulating in the community at the time.”
Safety data from the study also supported the vaccine’s potential as a booster. The most common side effects within seven days included local reactions at the injection site (52% tenderness, 30% pain), fatigue (29%), and muscle pain (29%). Serious adverse events were rare, with no deaths or severe events related to the vaccine. Unsolicited adverse events potentially linked to the vaccine occurred in only 2% of participants. Walker noted that this manageable safety profile aligns with expectations for vaccines targeting new strains. “It’s not surprising that this combination continues to perform well, optimizing the immune response and, therefore, providing better protection over time.”
The study involved 332 adults aged 18 years or older who had previously received three or more doses of mRNA vaccines. Participants received a single dose of NVX-CoV2601 via intramuscular injection. The primary endpoints were to demonstrate superiority in neutralizing antibody levels and non-inferiority in seroresponse rates compared to NVX-CoV2373. The study’s interim findings suggest that NVX-CoV2601 could serve as an effective booster, particularly for individuals who have received previous mRNA vaccinations.
Walker’s insights reinforce the importance of continuously updating vaccines to reflect emerging strains. He concluded, “This study helps to demonstrate that, yes, there's real value in updating the strain to match the circulating strain and providing better immune protection.”
These promising results align with global efforts to target emerging variants and underscore the need for adaptable, effective vaccines as COVID-19 continues to evolve. As Walker emphasized, “We make life-saving preventative vaccines for a range of infectious diseases, and we have an exciting and active research and discovery program ahead of us.”
