Filip Dubovsky
Analyst · B. Riley Securities
Thanks, John. Please turn to Slide 8. What's displayed here is the high-level 2373 clinical development plan. The safety, immunogenicity and efficacy of our vaccine is derived from these studies. And all these studies are part of our common clinical regulatory package that's included in our harmonized regulatory filings. This data has been provided to regulatory agencies on an ongoing basis and this is currently being reviewed.
Let's skip ahead to Slide 9. This slide highlights our 2 pivotal Phase III studies. The bulk of our safety and efficacy data is derived from these studies. One remarkable feature of our vaccine is the consistent efficacy we've seen. The primary vaccine efficacy estimates are within 1 percentage point of each other, and that's despite the fact these studies were conducted at different times in different populations during a time when different variants emerged. You can see a very high point estimate of efficacy, 96% to 100%, against match strains. These are strains whose sequences are most similar to that included in the vaccine. Additionally, the vaccine works well against variance, not only against alpha, but as we have detailed earlier in our U.S. Phase III study, against all variants that circulated at that time. Importantly, we have complete protection against severe disease, hospitalization and deaths in all of our efficacy studies, and that includes, again, severe disease caused by variants. In the larger U.S. study, our vaccine efficacy was 100% against severe disease. And in the smaller U.K. and South African studies, although we couldn't calculate an efficacy because of the low number of cases, all the severe cases were in placebo group. Finally, our efficacy in high-risk populations, such as the elderly and people with comorbid conditions, is almost identical to that of their overall population.
So now let's skip forward to Slide 10, talk about our progress in pediatrics. We expanded our U.S. Phase III study to include over 2,200 12- to 17-year-olds. All the primary vaccination series have been delivered. And in fact, all the children have been crossed over and safety and efficacy data collection is ongoing. We expect to have a regulatory package available for global submission in the first quarter. The subsequent pediatric clinical development plan has been agreed to by the FDA, MHRA and EMA and the studies will be initiated after this adolescent study reads out.
Okay, let's move on to Slide 11 and talk about boosting. In our Phase II study in the U.S. and Australia, we boosted select cohorts at 6 months and at 12 months and the 12-month doses are just finishing up now. We've previously disclosed that a single dose at 6 month can increase wild-type neutralization as well as IgG antibody levels more than fourfold from their peak after receiving 2 doses. However, more importantly, using a stringent human ACE2 inhibition assay, this measures functional antibodies, we demonstrated that our vaccine can boost responses to alpha, beta and delta 6.6 to 10.8 fold over their peak. We believe this is a strength of our vaccine, likely linked to our adjuvant system. We saw excellent protection in the Phase III studies against variants. And recently, Professor Snape from Oxford presented data that demonstrated that 2373 has a specific strength in inducing cross-variant neutralizing responses. In our South Africa Phase II study, we boosted all participants who initially received 2 doses of vaccine with a third dose at 6 months, and that safety data is maturing. The emergency data from the U.S., Australia, along with the safety data from our South Africa study will serve as the basis of our regulatory filings supporting our boosting indication.
Finally, let's move to Slide 12, and I want to update you on the progress of our Australia NanoFlu, our 2373 combination study. As you may know, we recently published an NanoFlu Phase III study this quarter in Lancet ID and the study met its primary endpoints, and we've been given a regulatory pathway for licensure by the FDA. The current study, the combination study, was designed to define the dosage levels in vaccination schedule for our quadrivalent flu HA antigen combined with our COVID antigen. Enrollment is complete. All the first doses have been delivered and the second doses are being currently administered. We believe that much like flu, COVID will continue to circulate. Our flu and COVID vaccine share immunologic attributes that make the vaccine attractive in providing protection against drifted flu strains as well as COVID variants. This data will be available in the first half of 2022.
I'd like to now turn it over to Jim to provide an overview of our financial results for the third quarter. Jim?