SAN FRANCISCO -- Ten out of the more than four million people who got the first doses of the Moderna COVID-19 vaccine had a severe allergic reaction, according to the Centers for Disease Control and Prevention, or CDC. "In all the cases no one has died and it's been all treatable. Most of them occurred within the first 10 minutes," said Peter Chin-Hong, a UCSF Infectious Disease specialist. Dr. Peter Chin-Hong says these cases are rare and added, "The allergic reaction are likely happening because the fatty bubble that incases the message and that messenger RNA vaccine might be an allergen to some people. But the good news is that it's not a lot of people," said Dr. Chin-Hong.