Participants in COVID-19 vaccine trials from both Pfizer and Moderna have reported more aggressive side effects in the second dose of the two-shot regimens expected to become available to Americans in the coming weeks.
The Food and Drug Administration is expected to approve Pfizer's vaccine within days, with Moderna's to follow after a December 17 meeting.
Multiple trial participants have warned that the second dose of the vaccine led to more severe, flu-like symptoms than the first. One man reported shaking violently in his bed to the point where he cracked a tooth. Others reported extreme fatigue, headache, and fever.
Yasir Batalvi, a 24-year-old participant in Moderna's trial, said the first shot caused mild "stiffness and pain" in his arm, but the second shot brought on more intense symptoms.
"After the injection, I had the same side effects as the first: localized pain and stiffness, but it was a little bit worse," said Batalvi. "My arm got sore faster, and by the time I got home, I started feeling fatigued and like anyone would feel if they were coming down with the flu. I developed a low-grade fever and had chills. That evening was rough."
Batalvi said he felt normal again by the afternoon of the next day.
Dr. Moncef Slaoui, who leads the Trump administration's vaccine development response, said that only 10% to 15% of volunteers had "significantly noticeable" side effects and stressed that the vaccines are safe for the general population. The FDA has said the same, saying there are "no specific safety concerns identified that would preclude issuance of an [emergency use authorization]."
There is also a small chance of an allergic response to the vaccines, demonstrated by the reactions of two medical workers in the U.K. who received the Pfizer vaccine on Wednesday. Both workers reportedly had histories of severe allergic reactions. Pfizer has warned that such individuals should not get the vaccine.
🔦 Last month, doctors from the American Medical Association urged vaccine makers like Pfizer and Moderna to be transparent about side effects and the potentiality of taking time off to recover after the second dose.