Pfizer Study Patient Says 2nd Vaccine Shot Hits Hard, 'Really Sick' but Not for Long

People who are getting the coronavirus vaccine don't know what's coming next -- that 2nd shot could hit like a ton of bricks, according to a guy who volunteered for Pfizer's study.

Eric Gross joined us on "TMZ Live" Thursday, and laid out his experience getting both doses of the vaccine during Pfizer's clinical trials. He said the first injection made his arm a little sore -- which we've heard from others this week -- but he says the 2nd shot is a whole different ballgame.

In Eric's experience, it left him feeling sicker than he's ever felt in his life, although not for too long. He has an analogy for his body's reaction -- think sucker punch in the face. Watch the vid, it's a great explanation.

As you know ... healthcare workers in America started getting the first round of vaccinations Monday and folks like Sandra Lindsay, the intensive care nurse who got the first shot in New York, told us so far, so good ... as far as any reactions or side effects.

Eric also talked to us about the story TMZ broke -- that volunteers who got the placebo during the trial pressured Pfizer to let them get the real deal.