News from the FDA/CDC

CDC panel: No COVID-19 vaccine safety surprises


The United States is nearly 6 weeks into its historic campaign to vaccinate Americans against the virus that causes COVID-19, and so far, the two vaccines in use look remarkably low risk, according to new data presented today at a meeting of vaccine experts that advise the Centers for Disease Control and Prevention.

With 23.5 million doses of the Pfizer and Moderna vaccines now given, there have been very few serious side effects. In addition, deaths reported after people got the vaccine do not seem to be related to it.

The most common symptoms reported after vaccination were pain where people got the shot, fatigue, headache, and muscle soreness. These were more common after the second dose. In addition, about one in four people reported fever and chills after the second shot.

“On the whole, I thought it was very reassuring,” said William Schaffner, MD, an infectious disease expert with Vanderbilt University, Nashville, Tenn., who listened to the presentations.

The CDC is collecting safety information through multiple channels. These include a new smartphone-based app called V-Safe, which collects daily information from people who’ve been vaccinated; the federal Vaccine Adverse Event Reporting System, which accepts reports from anyone; and the Vaccine Safety Datalink, which is a collaboration between the CDC and nine major hospital systems. There’s also the Clinical Immunization Safety Assessment Project, a collaboration between the CDC and vaccine safety experts.

After surveying these systems, experts heading the safety committee for the CDC’s Advisory Committee on Immunization Practices said there have been few serious side effects reported.

Very rarely, severe allergic reactions – called anaphylaxis – have occurred after vaccination. There have been 50 of these cases reported after the Pfizer vaccine and 21 cases reported after the Moderna vaccine to date. Nearly all of them – 94% of the anaphylaxis cases after Pfizer vaccines and 100% of those after Moderna’s vaccine – have been in women, though it’s not clear why.

That translates to a rate of about five cases of anaphylaxis for every million doses of the Pfizer vaccine and about three for every million doses of the Moderna vaccine. Most of these occur within 15 minutes after getting a vaccine dose, with one reported as long as 20 hours after the shot.

The CDC suspects these may be related to an ingredient called polyethylene glycol (PEG). PEG is a part of the particles that slip the vaccines’ mRNA into cells with instructions to make the spike protein of the virus. Cells then express these spikes on their surfaces so the immune system can learn to recognize them and make defenses against them. PEG is a common ingredient in many drugs and occasionally triggers anaphylaxis.

Reported deaths seem unrelated to vaccines

Through Jan. 18, 196 people have died after getting a vaccine.

Most of these deaths (129) were in patients in long term care facilities. These deaths are still being investigated, but when they were compared with the number of deaths that might be expected over the same period because of natural causes, they seemed to be coincidental and not caused by the vaccine, said Tom Shimabukuro, MD, deputy director of the Immunization Safety Office at the CDC, who studied the data.

In fact, death rates were lower among vaccinated nursing home residents, compared with those who had not been vaccinated.

“These findings suggest that short-term mortality rates appear unrelated to vaccination for COVID-19,” Dr. Shimabukuro said.

This also appeared to be true for younger adults who died after their shots.

There were 28 people aged under 65 years who died after being vaccinated. Most of these deaths were heart related, according to autopsy reports. When investigators compared the number of sudden cardiac deaths expected to occur in this population naturally, they found people who were vaccinated had a lower rate than would have been expected without vaccination. This suggests that these deaths were also unrelated to the vaccine.


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