He can't be sure of it, but it's the way it works, so its expected. Also, 2nd dose usually causes a stronger reaction from the body (you get the symptoms withou

He can't be sure of it, but it's the way it works, so its expected. Also, 2nd dose usually causes a stronger reaction from the body (you get the symptoms without the risks). See https://xkcd.com/2425 https://xkcd.com/2425