Photographer: Eva Marie Uzcategui / Bloomberg
Photographer: Eva Marie Uzcategui / Bloomberg
Like all new drugs, Covid-19 vaccines that have been authorized in Western countries have some safety concerns and side effects. Many people who received the first two shots, one from Pfizer Inc. and BioNTech SE and another Moderna Inc., had fever, headache and pain at the injection site. These side effects usually go away quickly. Up to 10 people have had a severe allergic reaction, called anaphylaxis, to vaccines.
1. What is anaphylaxis?
The body fights foreign invaders through a variety of mechanisms that include the production of protective proteins called antibodies, the release of toxins that kill microbes and the organization of guardian cells to fight infection. As with any conflict, sometimes the effort to ward off an infection can be harmful. In rare cases, it can produce uncontrolled inflammation and tissue swelling in a severe allergic reaction called anaphylaxis. As well as 5% of people in the US have had this reaction to various substances. It can be fatal if, for example, a person’s airways are closed, although deaths are rare. Allergies to insect bites and food can cause it, although reactions to medications are the most common cause of anaphylaxis fatalities in the US and the UK
2. Where did Covid’s vaccines trigger cases?
On December 19th The presentation by the US Centers for Disease Control and Prevention mentioned two cases of anaphylaxis associated with the Pfizer-BioNTech vaccine in the United Kingdom and six in the USA. An Alaskan healthcare professional who received an injection had to be hospitalized overnight. At the end of the month, in Israel, which is implanting the Pfizer-BioNTech vaccine, a man suffered anaphylactic shock one hour after receiving an injection, according to the Jerusalem Post. He said he had previous reactions to penicillin, the newspaper reported. And a doctor in Boston with a shellfish allergy reported having a anaphylactic reaction to Moderna’s vaccine. None of the reactions resulted in death.
3. Has anaphylaxis been associated with vaccines before?
Yes. 2016 study in the Journal of Allergy and Clinical Immunology found 33 confirmed cases of vaccine-triggered anaphylaxis that occurred after 25,173,965 doses of inoculations, a rate of about 1.31 per million doses. So far, the rate of known cases linked to the administration of approximately 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?
It is usually not long. Anaphylactic reactions typically occur within minutes to hours after exposure to a specific substance, said Michael Kinch, a specialist in drug development and associate vice president of Washington University in St. Louis. Of the 29 cases in which the time interval was documented in the 2016 study, symptoms of anaphylaxis started within 30 minutes in eight cases, within the next 90 minutes in another eight, within two to four hours in 10 cases, within four to eight hours in two cases and the next day in one.
5. What is being done about the risk?
The United Kingdom and the US has advised people who are allergic to any component of a Covid vaccine not to receive it. Anaphylaxis can be quickly combated with antihistamines and adrenaline injectors such as Epi-Pen from Mylan NV, which slow or stop immune reactions, and the health professionals who administer the vaccine keep these items at their disposal. These treatments do not cancel out the beneficial effects of vaccines. In the United States, healthcare professionals are watching anyone who has received the vaccine for at least 15 minutes after the injection to see if there are signs of a reaction. People who have had reactions to the first dose of the vaccine should not receive a second, according to the CDC.
6. Do we know what in the photos is causing the reactions?
This 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 of vaccines, according to Eric Topol, a specialist in clinical trials and director of the Scripps Research Translational Institute. Polyethylene glycol was previously associated with a handful of cases of anaphylaxis. Once the cause has been reduced, it may be possible to make Covid’s vaccines even safer than they are now, Topol said. If other serious non-allergic side effects arise, he said, “they will also be quite rare and the net benefit of vaccination is extremely positive.”