Covid-19: Second Covid mRNA vaccine dose found safe in people with allergic reaction to first dose

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  • People with allergic reactions to their first Covid mRNA vaccine dose had no serious complications after receiving the second dose.
  • The findings stem from a multi-hospital analysis in the US.
  • The researchers say that people who had a reaction after their first dose, therefore, shouldn't avoid getting the second dose.

People are encouraged to complete their vaccination series even if they had an allergic reaction to the first dose of the mRNA Covid-19 vaccines by Pfizer-BioNTech or Moderna.

According to researchers from Massachusetts General Hospital (MGH), a multi-hospital analysis of individuals who experienced anaphylaxis, a potentially life-threatening whole-body allergic reaction, after receiving their first mRNA Covid vaccine dose showed that they received their second dose without serious complications.

Based on this, the allergists are encouraging patients to complete their vaccination series. Several studies have also underscored the importance of receiving the second dose, as the first jab offers little protection against Covid-related severe disease and death. 

The US Centers for Disease Control and Prevention (CDC) recommends that individuals with an immediate and potential allergic reaction to the first dose of the Pfizer or Moderna vaccine should not get a second shot of that vaccine.

“However, our data suggest that most patients with immediate and potential allergic reactions to mRNA Covid-19 vaccines tolerate a second dose,” wrote the authors.

Their findings were published in JAMA Internal Medicine.

Rare occurrence

Anaphylaxis occurs in up to 2.5 per 10 000 people, according to the two researchers. 

Symptoms of a severe allergic reaction may include hives, swelling, and wheezing (respiratory distress) and the person may need to be treated with epinephrine or EpiPen©, or go to the hospital. 

In the study, the researchers combined data from patients who sought allergy specialist care at their hospitals after experiencing a reaction to their first mRNA Covid vaccine dose. 

Among 189 patients, 130 (69%) experienced reactions to Moderna and 59 (31%) to Pfizer’s vaccine after the first dose.

Flushing or erythema, dizziness or lightheadedness, tingling, throat tightness, hives, and wheezing or shortness of breath were the most frequently reported symptoms after the first dose.

The following was noted:

  • 32 (17%) met the criteria for anaphylaxis after their first dose of the mRNA vaccine. 
  • A total of 159 patients (84%) went on to receive a second dose – antihistamine premedication before the second dose was given in 47 patients (30%).
  • All 159 individuals, including the 19 who had experienced anaphylaxis following the first dose, tolerated the second dose.
  • 32 (20%) reported immediate and potentially allergic symptoms associated with the second dose, but these were self-limited, mild, and/or resolved with antihistamines alone. 

Comments from author

The study’s findings suggest that it’s safe for most individuals to receive a second dose of the mRNA Covid vaccine, co-author Dr Aleena Banerji, Associate Professor at Harvard Medical School, and also the clinical director of the Allergy and Clinical Immunology Unit at MGH, said in a news release

“After first dose reactions, allergy specialists may be useful to help guide risk/benefit assessments and assist with completion of safe vaccination,” she added.

Monitoring after vaccination

Everyone who gets the vaccine is generally monitored for 15 minutes on-site. 

People who have had any type of immediate allergic reaction to a vaccine in the past,  or to an injectable therapy for another disease, should inform the healthcare personnel administering the vaccine so that they can be monitored for at least 30 minutes after being vaccinated. 

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

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