What happened

Shares of VBI Vaccines (VBIV -1.56%) were up 45% as of 11:18 a.m. EDT on Thursday after rising as much as 62% earlier in the session. The huge jump came after Raymond James analyst Steven Seedhouse upgraded the stock from outperform to strong buy and raised his price target from $8 to $9.

So what

Analyst upgrades usually help stocks -- and especially small biotech stocks. But the massive gain for VBI Vaccines is certainly out of the ordinary.

Rocket flying over a red line with an arrow trending upward

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The main reason why investors are so excited stemmed more from the comments by the analyst than the upgrade itself. Seedhouse stated in a note to investors that VBI's COVID-19 vaccine candidate "could be the best vaccine of them all (including all of the first movers and Operation Warp Speed members)." The research note added, "VBI may be in an entirely different ballpark for potency vs. any other vaccine we've seen."

If this take is right, VBI could eventually become the leader among all of the drugmakers with novel coronavirus vaccines in development. It's important to note, though, that Seedhouse's optimism is based solely on preclinical data. Clinical testing in humans doesn't always produce results similar to those seen in preclinical testing.

Now what

Investors shouldn't have to wait for too long to know how VBI's COVID-19 vaccine fares in clinical testing. The company has selected two vaccine candidates to advance into a phase 1/2 clinical study. Assuming VBI receives a green light from the FDA, the study will likely begin in late 2020.