What to Know About Blood Clots, Anaphylaxis and Other Vaccine Fears
(Bloomberg) -- Covid vaccines are designed to prevent a disease that has so far killed nearly 3 million worldwide. No pharmaceutical, however, is completely benign. The goal is to ensure the benefits outweigh the risks. So far, the vaccines have been connected to a relatively small number of cases of blood clots and serious, but treatable allergic reactions called anaphylaxis. Other concerns -- about vaccinations causing temporary facial paralysis, heart inflammation and otherwise unexplained deaths -- have either not proven justified or are still under investigation.
1. What happened with the blood clots?
Two vaccines, one from Johnson & Johnson and another from AstraZeneca Plc, have been associated with very rare reports of an unusual clotting syndrome. The syndrome, which occurs more often in young people, is atypical because it occurs alongside low levels of blood platelets -- the key element in formation of blood clots. Several countries, mainly in Europe, suspended use of the AstraZeneca vaccine or restricted its administration in younger people. U.K. health authorities advised that those younger than 30 be offered an alternative vaccine, if available. Regulators there put the overall risk of the clots at about 4 in a million people who receive the vaccine. In the U.S., health officials paused use of the J&J vaccine to assess the side effect and raise doctors’ awareness of how to recognize and treat it. Use of the vaccine resumed in April, and the U.K. authorized it in May.
2. What are signs to watch for?
People who have received the shots two to four weeks earlier should watch for symptoms that may prefigure the onset of clotting. These include shortness of breath, chest pain, leg swelling, persistent belly pain, severe headaches, blurred vision and tiny blood spots under the skin beyond the vaccine injection site.
3. What’s causing the clots?
U.K. health officials described the syndrome as similar to a rare side effect of treatment with heparin, an anticoagulant, in which the body forms antibodies against platelets. How or why the vaccine might be involved in such a process is still under investigation. Researchers are looking at whether the side effect is related to a harmless version of an adenovirus, a cold virus, that’s included in both the J&J and AstraZeneca shots. The adenovirus delivers a gene that instructs cells to make the spike protein that gives the coronavirus that causes Covid its crown-like appearance. This, in turn, stimulates the body to mount immune responses to the virus, so that it is primed for a fight if it ever encounters the real thing. Russia’s Sputnik V vaccine and another from China’s CanSino Biologics also use an adenovirus platform.
4. What about the serious allergic reactions? What accounts for them?
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. As of May 24 in the U.S., no deaths had been connected to Covid vaccines, from anaphylaxis or any other reaction.
5. How often have Covid vaccines triggered cases?
In the U.S., according to the Centers for Disease Control and Prevention, 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. 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 anaphylactic 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.
8. What about the cases of Bell’s palsy?
In studies testing the Moderna and Pfizer-BioNTech inoculations, more people developed Bell’s palsy, which typically affects just one side of the face, after receiving vaccine doses than placebo shots. The imbalance turned out not to be substantiated, however, based on the massive safety database the CDC has collected on millions of people vaccinated since the drugs were authorized for the general public. Also, the drugs regulator in the U.K., where the Pfizer-BioNTech formulation is one of two in use, noted that as of March 28, the number of reports of Bell’s palsy among those vaccinated does not suggest an increased risk.
9. How did concerns about heart inflammation come to light?
Israeli health officials have found a probable link between the Pfizer-BioNTech vaccine and dozens of cases of heart inflammation in young men, often following the second dose of the vaccine, the Health Ministry said June 1. There were 275 cases of myocarditis, or inflammation of the heart tissue, identified between December 2020, when the vaccination drive began, and May 2021, officials said, and 148 of these occurred within a month after vaccination. About half were in people with previous medical conditions. Coronavirus cases have plummeted in Israel since the country’s campaign began, and more than 5 million people in the country have received shots.
10. What’s known about deaths after vaccinations?
- 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 developed by 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.”
- The U.K.’s Medicines and Healthcare Products Regulatory Agency reported that, through March 28, there were 302 deaths shortly after injections with the Pfizer-BioNTech vaccine, 472 after the AstraZeneca shot and 12 where the brand was unspecified. The deaths were mainly in elderly people or those with underlying illness, and the evidence does not suggest the vaccines played a role, it said. However, the agency’s April analysis of blood clots after vaccinations reported 19 deaths among 79 cases and officials said further study was needed.
- Germany’s medical regulatory body, 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.
- In the U.S., which is using vaccines from Pfizer-BioNTech, Moderna Inc. and Johnson & Johnson, the Centers for Disease Control and Prevention said that as of May 24, there were 4,863 reported deaths among inoculated people, a rate of 0.002%, and no causal link had been established. It did note a plausible connection between the J&J vaccine and blood clots, which have caused deaths.
- Authorities in Hong Kong, which has mostly deployed a vaccine from China’s Sinovac Biotech Ltd., have reported six deaths among more than 150,000 people inoculated. None have been connected to vaccines.
11. Have other new vaccines had safety issues?
Before regulatory authorities authorize a new vaccine, it must be tested both for safety and efficacy in thousands of human volunteers. Still, there have been cases where safety issues have arisen after authorization. European regulators in 2011 recommended restricting the use of a new swine-flu vaccine from GlaxoSmithKline Plc after it was linked to rare cases of narcolepsy. A vaccine against Lyme disease developed by the same company, then called SmithKline Beecham, was pulled in 2002 amid concerns about links to arthritis. Some vaccines have been shown to do the opposite of what they’re designed to do by inducing unwanted immune responses. In recent years, Sanofi’s vaccine against dengue, which can infect a person as many as four times, was found to cause more severe disease in those who become infected for the first time after getting the inoculation. Documented reports of unexpected side effects from novel vaccines are different from the persistent and incorrect belief that well-established vaccines against childhood diseases carry significant risks.
The Reference Shelf
- Related QuickTakes on vaccine nationalism, vaccine mandates, vaccine hesitancy, mRNA vaccines, why it’s difficult to compare Covid vaccines, and vaccine trade secrets.
- A radio discussion with Sam Fazeli of Bloomberg Intelligence on vaccines.
- The CDC’s morbidity and mortality weekly reports.
- An article in Stat puts the allergic reactions in context.
- Researchers take a deep dive into safety issues in the journal Vaccines.
- Follow the inoculation rollout using Bloomberg’s Vaccine Tracker.
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