Photographer: Eva Marie Uzcategui / Bloomberg
Photographer: Eva Marie Uzcategui / Bloomberg
Like all new drugs, the Covid-19 vaccines approved in Western countries pose some safety concerns and side effects. Many people who received the first two shots have been deployed, one of them Pfizer Inc. and BioNTech SE and another from Moderna Inc. has experienced fever, headache, and pain at the injection site. These side effects usually disappear quickly. As many as 10 people have had a serious allergic reaction called anaphylaxis to the vaccines.
1. What is anaphylaxis?
The body fights off foreign invaders through a variety of mechanisms, including making protective proteins called antibodies, releasing toxins that kill microbes, and arranging protective cells to fight infection. As with any conflict, trying to fend off an infection can sometimes itself be harmful. In rare cases, it can cause runaway inflammation and swelling of tissues called a severe allergic reaction anaphylaxis. As much as 5% of people in the US have had such a reaction to various substances. It can be fatal if, for example, the person’s airways swell even though there have been deaths special. Allergies to insect stings and food can cause it, although drug reactions are most common cause of deaths from anaphylaxis in the US and UK
2. Where have Covid vaccines caused cases?
A December 19 presentation of the US Centers for Disease Control and Prevention referred to two cases of anaphylaxis associated with the Pfizer-BioNTech vaccine in the UK and six in the US. A health worker in Alaska who received an injection had to be hospitalized overnight. Later in the month, in Israel, which is deploying the Pfizer-BioNTech vaccine, a man went into anaphylactic shock an hour after receiving an injection. according to the Jerusalem Post. He said he had had previous reactions to penicillin, the paper reported. And a doctor in Boston with a shellfish allergy reported one anaphylactic reaction to Moderna’s vaccine. None of the responses resulted in death.
3. Has anaphylaxis been previously associated with vaccines?
Yes. A 2016 study in the Journal of Allergy and Clinical Immunology found 33 confirmed cases of vaccine-induced anaphylaxis that occurred after 25,173,965 doses of inoculations, a rate of about 1.31 per million doses. So far, the rate for known cases related to administration is approx 3 million doses of the Pfizer and Moderna vaccines appear to be more than double, but still very low.
4. How long does the risk last?
Usually not long. Anaphylactic reactions normally occur within minutes to hours of exposure to a specific substance, said Michael Kinch, a drug development expert and associate vice chancellor at Washington University in St. Louis. Of the 29 cases where the delay was documented in the 2016 study, in eight cases the symptoms of anaphylaxis started within 30 minutes, in another eight cases within 90 minutes, in 10 cases within two to four hours, within four to eight hours in two cases, and the next day in one.
5. What is done about the risk?
The UK and the US has advised people allergic to any component of a Covid vaccine not to get it. Anaphylaxis can be rapidly controlled with antihistamines and adrenaline injectors such as Mylan NV’s Epi-Pen that slow or stop immune responses, and health professionals administering the vaccine keep such products on hand. These treatments do not cancel out the beneficial effects of vaccines. In the US, health professionals observe anyone who has received the vaccine for at least 15 minutes after the injection to look for signs of a reaction. People who have had reactions to a first dose of vaccine are allowed to, according to the CDC.
6. Do we know what causes the reactions in the shots?
That is not clear. The two main candidates are polyethylene glycol – a chemical found in many foods, cosmetics and medicines – and lipid nanoparticles that encapsulate messenger RNA, a genetic component in the vaccines, according to Eric Topol, a clinical trial expert and director of the Scripps Research Translational Institute. Polyethylene glycol has been previously linked to a handful of cases of anaphylaxis. Once a cause has been narrowed down, it may be possible to make Covid vaccines even safer than they are now, Topol said. If there are other serious non-allergic side effects, he said, “These are probably quite rare, too, and the net benefit of vaccination is overwhelmingly positive.”