VBI Vaccines (VBIV) has had a tough week, but it could still have a good end to the year. Despite its flagship hepatitis B vaccine candidate Sci-B-Vac demonstrating superiority to GlaxoSmithKline's (GSK) standard-of-care Engerix-B across almost all metrics, the stock plummeted by almost two thirds on news that two doses of Sci-B-Vac did not achieve statistical noninferiority to 3 doses of Engerix-B for all patients. Specifically, 66% of Sci-B-Vac patients achieved seroprotection against the virus after 2 doses, versus 76.5% of Engerix-B patients after 3 doses.
Why should VBI fall so precipitously on this news if primary endpoints were hit and every other measurement showed superiority of Sci-B-Vac over Engerix-B? Because competitor Dynavax (DVAX) already has a 2-dose vaccine – Heplisav-B – that is superior in efficacy to Engerix-B on the market.
Heplisav-B has two main advantages that theoretically carve out a market for it. The first is that it is significantly more efficacious than Engerix-B at achieving seroprotection in immunocompromised patients like diabetics, the obese, and the elderly. The second is that as much as 75% of adults who take Engerix-B do not receive all three doses of vaccine, at least according to Dynavax (see slide 5). It's a main marketing point for the vaccine.
Since the seroprotection rate for Engerix-B after two doses is less than 60% in these immunocompromised patient populations, that means that 40% of these people are prone to HBV infection, damaging the all-important factor of herd immunity that is critical for disease eradication. It's one of the big reasons that HBV infection is still a global problem. Heplisav-B can theoretically help solve this problem by immunizing the immunocompromised after only two doses.
So, if Sci-B-Vac can only achieve superiority to Engerix-B in the immunocompromised after three doses but not two, then it is missing a key
