Pfizer’s new coronavirus vaccine is beginning to roll out with some side effects, including that it will give male recipients a massive and long-lasting erection – but Pfizer insists that’s not a side effect to worry about.

“It’s a feature, not a bug,” Pfizer said in a statement Thursday. “Men who take the vaccine may end up with the biggest erection of their lives, and it may last for more than four hours, but the vaccine won’t work unless this is the case. With how fast we developed this, we couldn’t figure out a way to produce it without boners.”

Early trials have shown massive, 5-hour erections in 99% of men, with some lasting a full day. Of those 99% of men, 99% have said it’s worth the protection against the virus.