Like all new drugs, the vaccines that have been authorized to protect against COVID-19 come with some safety concerns and side effects. Many people who’ve received the shots have experienced fever, headache, and pain at the site of the injection. These side effects generally disappear quickly. A small number of vaccine recipients have had a serious, but treatable, allergic reaction, called anaphylaxis. A few countries have reported deaths following administration of COVID-19 vaccines, but medical specialists have found no evidence of a connection to the inoculations.
1. What’s known about the deaths?
Norwegian officials were the first to report people dying after being inoculated, saying in mid-January that 33 people age 75 and older had died a short time after receiving the COVID vaccine from Pfizer Inc. and BioNTech SE. After a review, a committee of the World Health Organization said that the fatalities were “in line with the expected, all-cause mortality rates and causes of death in the sub-population of frail, elderly individuals.” The committee concluded that the risk-benefit balance of the vaccine “remains favorable in the elderly.”
2. Where else have deaths been investigated?
The U.K.’s Medicines and Healthcare Products Regulatory Agency reported that as of Jan. 24, there were 143 deaths shortly after injections with the Pfizer-BioNTech vaccine and another from AstraZeneca Plc, mainly in elderly people or those with underlying illness, and that there’s no suggestion the vaccines played a role. In Germany, the Paul Ehrlich Institute said after an investigation that the deaths of seven elderly people shortly after receiving the Pfizer-BioNTech vaccine were probably due to the patients’ underlying diseases. And in the U.S., the Centers for Disease Control and Prevention said that as of Feb. 7, there were 1,170 reported deaths among people who received either the Pfizer-BioNTech vaccine or another from Moderna Inc., a rate of 0.003%, and no evidence suggests a link.
3. What accounts for the serious allergic reactions?
The body fights foreign invaders through a variety of mechanisms that include making protective proteins called antibodies, releasing toxins that kill microbes, and marshaling guardian cells to battle the infection. As in any conflict, sometimes the effort to repel an infection can itself be damaging. In rare cases, it can produce runaway inflammation and swelling of tissues in a serious allergic reaction called anaphylaxis. As much as 5% of the U.S. population has had such a reaction to various substances. It can be fatal if, for example, the person’s airway swells shut, though deaths are rare. Allergies to insect stings and foods can provoke it, though drug reactions are the most common cause of anaphylaxis fatalities in the U.S. and U.K.
4. How often have COVID vaccines triggered cases?
In the U.S., according to the CDC, it occurs in just 2 to 5 people for every million receiving a COVID vaccine. The risk of contracting COVID outweighs that posed by the vaccines, officials and clinicians say. Anaphylaxis is a known risk of vaccination. Such reactions occur about 1.3 times per million doses of flu vaccine administered. With other vaccines they have been seen at rates of 12 to 25 per million doses, though the studies were small.
5. How long does the risk of allergic reaction last?
Usually not long. When anaphylaxis occurs, it is almost always within half an hour of administering the vaccine, according to the CDC.
6. What’s being done to manage the risk?
The U.K. and U.S. have advised people who have allergies to any component of a COVID vaccine not to receive it. Anaphylaxis can be quickly countered with antihistamines in tandem with adrenaline injectors like Mylan NV’s Epi-Pen that slow or halt immune reactions, and health workers giving the vaccine are keeping such items at the ready. These treatments don’t cancel out the beneficial effects of vaccines. In the U.S., health workers are observing everyone who receives the vaccine for at least 15 minutes post-injection to watch for signs of a reaction; those with a worrying history of allergic reaction are monitored for twice as long. People who have had reactions to a first dose of vaccine shouldn’t receive a second, according to the CDC.
7. Do we know what in the shots is causing the reactions?
That isn’t clear. Two leading candidates are polyethylene glycol—a chemical found in many foods, cosmetics and medications—and lipid nanoparticles that encapsulate the messenger RNA, a genetic component in the Moderna and Pfizer-BioNTech vaccines, according to Eric Topol, a clinical trials expert and director of the Scripps Research Translational Institute. Polyethylene glycol has been previously linked to a handful of anaphylaxis cases. Once a cause has been narrowed down, it may be possible to make COVID vaccines even safer than they are now, Topol said.
The reference shelf
- Related QuickTakes on virus mutations, how the virus spreads, guidance on masking, what vaccines can and can’t achieve, vaccine passports, and the risks of flying during the pandemic.
- Sam Fazeli of Bloomberg Intelligence examines death rates in the U.S.
- The CDC’s morbidity and mortality weekly reports.
- An article in Stat puts the allergic reactions in context.
- Researchers take a deep dive into issues related to vaccine safety in an article in the journal Vaccines.
- Follow the inoculation rollout using Bloomberg’s Vaccine Tracker.