A new study demonstrated continuous neutralization after 3 doses.
As the Omicron variant continues to mutate, questions of vaccine efficacy and dosing schedules will continue to follow all the FDA approved and authorized COVID-19 vaccines. To address these points, the FDA is having its first Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting of the year on Thursday. And during the meeting, the FDA is going to report data on the efficacies of the currently approved and authorized vaccines, and consider a different dosing schedule for COVID-19 vaccines and look to emulate the current annual influenza vaccines offered during the fall.
According to the agenda, they “will consider questions around simplifying the composition/dosing regimen of the authorized/approved COVID-19 vaccines, the process for determining the need for recommending strain updates for COVID-19 vaccines, and the timing for implementation of a potential strain-based composition change.”
Included in the meeting will be data on the NVX-CoV2373 (Nuvaxovid) COVID-19 vaccine manufactured by Novavax. The vaccine was granted an emergency use authorization by the FDA last summer.
In a new study, investigators examined the Novavax vaccine and looked at 2 and 3 doses and its ability to demonstrate protection against the Omicron variants. They showed the vaccine, “enhanced neutralization of Omicron BA1 and BA4/BA5 following 3 doses of the NVX-CoV2373 vaccine with responses comparing well to 3 doses of an mRNA vaccine.”
The study results were published this week in Nature.
The investigators also noted that 6 months after 2 doses of the Novavax vaccine, it demonstrated increased binding antibodies, and “that responses after the third dose may mature further.”
The investigators collected the sera of 52 people with 37% of them being female and 50% of them were under 29 years of age. Using a spike-pseudotyped assay, they tested neutralization of the ancestral D614G, Beta, Omicron BA.1 and Omicron BA.4/BA.5 by the vaccinee sera following a 2 dose (n = 29) and 3 dose (n = 48) regimen.
“Fourteen days after two doses of NVX-CoV2373, geometric mean titers (GMT) were highest against the D614G variant (GMT: 1,401), with reductions in GMT to 173 (8.1-fold reduction), 34 (41-fold reduction) and 47 (30-fold reduction) against Beta, Omicron BA.1 and Omicron BA.4/BA.5 respectively,” the investigators wrote. “For the Omicron sub-lineages BA.1 and BA.4/BA.5, titers were lower than the limit of detection of the assay for 72% (21/29) and 59% (17/29) of samples, respectively, after the 2nd dose of vaccine.”
They also reported other positive findings. “The two dose NVX-CoV2372 vaccine regimen elicits robust memory CD4+ and CD8+ T cell responses in 100% and 65% of individuals respectively. In addition, the two dose regimen induces antibodies with multiple Fc-mediated functions, which in non-human primate and human cohorts likely contribute to protection from infection,” they wrote.
Important to note, this study did not include the XBB115 variant, which is widely circulating now. As of the end of December 2022, the Centers for Disease Control and Prevention found XBB15 was responsible for 40.5% of new COVID-19 infections. And in the northeastern part of the United States, the federal agency estimated the variant caused 75% of new infections.