It is safe for people who experienced an allergic reaction to the first dose of a COVID-19 vaccine to receive the second dose, a new study suggests.
Researchers from Massachusetts General Hospital (MGH) looked into hospital data from people who reported allergic reactions to the first shot of either Pfizer or Moderna.
They found that only a third of patients had an allergic reaction to the second dose after having one to the first, and the reactions were relatively minor.
The findings add to the growing knowledge about the vaccines, and their potential effects on people over time.
Receiving a second dose of the COVID-19 vaccine is particularly important as well, as some research shows only one dose of a vaccine may not be effective against the Indian ‘Delta’ variant.
Researchers found that people who developed an allergic reaction to the first dose of a COVID-19 vaccine are safe to receive the second dose
For the study, published in JAMA Internal Medicine, the team investigated data from patients who went to an allergy specialist after receiving their first dose for a potentially life-threatening whole-body allergic reaction.
Around 2.5 out of every 10,000 people, or 0.025 percent, will experience this type of reaction from the shot.
‘These reactions could include symptoms such as itching or hives or flushing. The patients included were all advised by allergy specialists after their dose one reaction,’ said Dr Matthew Krantz, co-lead author and allergy immunology fellow at Vanderbilt University, in a statement.
Of 189 patients who were vaccinated between January 1 and March 31, a total of 159 – or 84 percent – still received the second dose of the vaccine.
Among that group, 32 patients (20 percent) reported allergic symptoms to the second dose.
However, the reactions were relatively minor and resolved with antihistamines.
‘One important point from this study is that these immediate onset mRNA vaccine reactions may not be mechanistically caused by classic allergy, called immediate hypersensitivity or Ig-E-mediated hypersensitivity,’ said Dr Kimberly Blumentha, co-author and director of the Clinical Epidemiology Program within MGH’s Division of Rheumatology, Allergy and Immunology.
‘For classic allergy, re-exposure to the allergen causes the same or even worse symptoms.’
Of the group who experienced reactions, 130 (69 percent) received the Moderna shots and 31 percent received the Pfizer-BioNTech vaccine.
The most common first dose reactions recorded were erythema (28 percent of people) – where a person develops rashes on the skin – dizziness (26 percent), tingling (24 percent), throat tightness (22 percent) and hives (21 percent).
Researchers recommend for people who had an allergic reaction to still receive the second dose, but consult with their allergy specialist first.
Experts recommend that everyone complete their vaccine series – two doses for the Pfizer-BioNTech and Moderna vaccines and one for the Johnson & Johnson vaccine – whenever possible.
Completing a vaccine series produces more anti-bodies for a person, and provides higher efficacy in preventing complications from the virus.
Some research shows that only receiving one dose of a vaccine will even leave a person vulnerable to the Delta variant, a highly contagious virus variant that is sweeping across the nation.
The variant accounts for around 70 percent of active cases in the United States.
Currently, around 56 percent of Americans have received one dose of a COVID-19 vaccine, and just under 50 percent are fully vaccinated.
Every American aged 12 or older is eligible to receive a COVID-19 vaccine.
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