What happened

Shares of VBI Vaccines (VBIV -1.71%) were vaulting 5.9% higher as of 11:19 a.m. EST on Friday after rising as much as 20.5% earlier in the day. The nice gain came after the company announced positive results from a phase 4 study of its three-antigen hepatitis B virus (HBV) vaccine Sci-B-Vac in younger adults.

So what

VBI said that Sci-B-Vac achieved a seroprotection rate of at least 95% in adults between the ages of 20 and 40 within two months after the second dose of the vaccine. This reflected relatively quick protection against HBV infection in younger adults.

Gloved hands holding a syringe with a "hepatitis B" label on it

Image source: Getty Images.

Sci-B-Vac has already been approved and launched commercially in Israel. The phase 4 study was conducted in support of establishing the batch included in the study as a new reference standard. Before vaccines are made available in Israel, they must first be tested against a reference vaccine batch that has been evaluated in a clinical study.

Investors' enthusiastic reaction to VBI's news, though, probably didn't relate much to the prospects for Sci-B-Vac in Israel. The company hopes to win regulatory approvals for the vaccine in the U.S., Canada, and Europe. The positive phase 4 results no doubt increased investors' optimism that VBI will be successful in expanding the markets for Sci-B-Vac.

Now what

The European Medicines Agency (EMA) accepted VBI's filing for approval of its HBV vaccine in December. VBI also submitted a Biologics Licensing Application (BLA) to the U.S. Food and Drug Administration (FDA) last month. The next big catalyst for the biotech stock could come later this year if Sci-B-Vac gets a thumbs-up from the FDA and/or the EMA.