Jan 27, 2021 – The US is nearly 6 weeks in its historic campaign to vaccinate Americans against the virus that causes COVID-19. So far, according to the new data presented today, the two vaccines used look remarkably low risk at a meeting of vaccine experts advising the CDC.
With 23.5 million doses of the Pfizer and Moderna vaccines now being given, there have been very few serious side effects. In addition, deaths reported after receiving the vaccine do not appear to be related to it.
The most common symptoms reported after vaccination were pain that caused people to be shot, fatigue, headache, and sore muscles. These were more common after the second dose. In addition, about 1 in 4 people reported fever and chills after the second shot.
“On the whole, I found it very comforting,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical School in Nashville, who heard the presentations.
The CDC gathers security information through several channels. This includes a new smartphone-based app called V-Safe, which collects information from vaccinated people on a daily basis. the Federal Vaccine Adverse Event Reporting System (VAERS), which accepts reports from anyone; and the Vaccine Safety Datalink, a collaboration between the CDC and nine major hospital systems. There’s also CISA, the Clinical Immunization Safety Assessment Project, a collaboration between the CDC and vaccination safety experts.
After examining these systems, experts who chair the safety committee of the CDC’s Advisory Committee on Immunization Practices said few serious adverse reactions have been reported.
Very rarely have severe allergic reactions known as anaphylaxis occurred after vaccination. So far, 50 of these cases have been reported after the Pfizer vaccine and 21 cases after the Moderna vaccine. Almost all of them – 94% of anaphylaxis cases after Pfizer vaccines and 100% of cases after Moderna’s vaccine – had occurred in women, although it is not clear why.
This corresponds to a rate of about five cases of anaphylaxis for every million doses of Pfizer vaccine and about three for every million doses of Moderna vaccine. Most of these occur within 15 minutes of receiving a vaccine dose, with one reported up to 20 hours after the shot.
The CDC suspects these could be related to an ingredient called polyethylene glycol, or PEG. PEG is part of the particles that deliver vaccine mRNA into cells with instructions on how to make the virus’ spike protein. Cells then express these spikes on their surfaces so the immune system can learn to recognize them and defend itself against them. PEG is a common ingredient in many medications and occasionally causes anaphylaxis.
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