Anaphylaxis is a severe multisystem reaction that occurs rapidly after the introduction of an
antigen that would otherwise be a harmless substance. It is characterized by airway and respiratory problems, cardiovascular collapse, mucosal
inflammation, and other complications, all severe symptoms that can cause death.
IgE-dependent
anaphylaxis involves mast cells (MCs) which are the main sources of biologically active mediators that contribute to the pathological and lethal phenomena that can occur in
anaphylaxis. Antibody-mediated
anaphylaxis can follow multiple pathways such as that mediated by MCs carrying the FcεRI receptor, which can be activated by very small amounts of
antigen including a
vaccine antigen and trigger an
anaphylactic reaction. In addition,
anaphylaxis can also be provoked by high concentrations of
IgG antibodies that bind to the FcγR receptor present on basophils, neutrophils, macrophages and MCs. For this reason, the
IgG concentration should be kept under control in vaccinations. Activation of MCs is a major cause of
anaphylaxis, which requires immediate treatment with
epinephrine to arrest severe lethal symptoms. MCs are activated through the
antigen binding and cross-linking of
IgE with release of mediators such as
histamine,
proteases,
prostaglandins,
leukotrienes and inflammatory
cytokines. The release of these compounds causes
nausea,
vomiting,
hives,
wheezing,
flushing,
tachycardia,
hypotension,
laryngeal edema, and cardiovascular collapse.
mRNA and viral vector
vaccines have been cleared by the United States, Food and Drug Administration (FDA), generating hope of prevention and cure for
COVID-19 around the world. Scientists advise against giving the
vaccine to individuals who have had a previous history of
anaphylaxis. The US Centers for Disease Control and Prevention (CDC) advises people with a previous history of any immediate
allergic reaction to remain under observation for approximately 30 minutes after
COVID-19 vaccination. To date,
vaccines that prevent
SARS-CoV-2 infection have not raised major concerns of severe
allergic reactions, although, in some cases,
pain and redness at the injection site and
fever have occurred after administration of the
vaccine. These reactions occur in the first 24-48 hours after vaccination. It has been reported that probable forms of
anaphylaxis could also occur, especially in women approximately 40 years of age. But after
tens of millions of vaccinations, only a few patients had this severe reaction with a low incidence. Anaphylactic and severe
allergic reactions can also occur to any component of the
vaccine including
polysorbates and
polyethylene glycol. To date, there is no precise information on
allergic reactions to
COVID-19 vaccines. Individuals with MCs and
complement with higher activation than others may be at greater allergic risk. Moreover, the reactions called anaphylactoids, are those not mediated by
IgE because they do not involve this antibody and can also occur in
COVID-19 vaccination. These not-
IgE-mediated reactions occur through direct activation of MCs and
complement with
tryptase production, but to a lesser extent than
IgE-mediated
anaphylaxis. However, at the moment it is not known exactly which component of the
vaccine causes the
allergic reaction and which
vaccine causes the most side effects, including
anaphylaxis. Thus, individuals who have a known
allergy to any component of the
vaccine should not be vaccinated. However, should an
anaphylactic reaction occur, this requires immediate treatment with
epinephrine to arrest severe lethal symptoms. In conclusion, the purpose of this editorial is to encourage the population to be vaccinated in order to extinguish this global pandemic that is afflicting the world population, and to reassure individuals that
anaphylactic reactions do not occur with a higher incidence than other vaccinations.