The COVID-19 Task Force does not anticipate any contraindication for patients on allergen immunotherapy (AIT). However, it would be best to not get the two shots within 48 hours of each other to avoid confusion should a reaction occur. 

An NIAID clinical trial is underway to study allergic reactions to the Moderna and Pfizer-BioNTech COVID-19 vaccines.  PDF icon A brief synopsis of the study is available herePDF icon A flyer about the study is available here.

AAAAI COVID-19 Response Task Force Guidance on Administration of COVID-19 Vaccines Related to Concerns of Allergic Reactions


The CDC has updated their guidance on administration of the SARS-CoV-2 mRNA vaccines with respect to pre-vaccine risks and post-vaccine reactions. The CDC has provided the following differentiation: 

  • Contraindication: Persons with a known (diagnosed) allergy to PEG or polysorbate have a contraindication to vaccination. 
  • Precaution: Persons with a reaction to a vaccine or injectable therapy that contains multiple components, one of which is PEG, another mRNA vaccine component or polysorbate, but in whom it is unknown which component elicited the immediate allergic reaction have a precaution (counseling, 30-minute observation). Deferral of vaccination and/or consultation with an allergist may be considered. (Pfizer-BioNTechModerna
  • Immediate allergic reaction is defined as any hypersensitivity-related signs or symptoms such as urticaria, angioedema, respiratory distress (e.g., wheezing, stridor), or anaphylaxis that occur within four hours following administration. 
  • Individuals with a history of immediate allergic reaction to any component of an mRNA COVID-19 vaccine should not be vaccinated unless they have been evaluated by an allergist/immunologist and it is determined that the person can safely receive the vaccine (e.g., under observation, in a setting with advanced medical care available). 
  • Individuals with an immediate allergic reaction to the first dose of an mRNA vaccine should not receive additional doses of either of the mRNA COVID-19 vaccines. 
  • Individuals with a history of food, pet, insect, venom, environmental or latex allergies can proceed with vaccination with a standard 15-minute observation period. 
    • Vial stoppers of mRNA vaccines are not made with natural rubber latex 
    • The mRNA vaccines do not contain egg or gelatin 
  • Those with a history of severe allergic reaction (e.g. anaphylaxis) to an injectable medication should use caution when receiving the vaccine and follow a 30-minute observation period. 
  • These articles provide additional information on reactions: 
    • Maintaining Safety with SARS-CoV-2 Vaccines (NEJM, December 30, 2020) 
    • Allergic Reactions Including Anaphylaxis after Receipt of the First Dose of Pfizer-BioNTech COVID-19 Vaccine – United States, December 14-23, 2020 (MMWR, January 6, 2021) 
    • Allergic Reactions Including Anaphylaxis After Receipt of the First Dose of Moderna COVID-19 Vaccine – United States, December 21, 2020 – January 10, 2021 (MMWR, January 29,2021) 
    • Allergic Reactions Including Anaphylaxis After Receipt of the First Dose of Pfizer-BioNTech COVID-19 Vaccine (JAMA, January 21, 2021) 
  • There are multiple systems for monitoring adverse reactions to the COVID-19 vaccine (December 10, 2020) 

Other Reported Reactions


After a thorough safety review the ACIP, CDC and FDA agree that the known and potential benefits from the J&J vaccine outweigh the rare risk of the thrombotic complications that have been reported. Use of the vaccine will resume for all people 18 years of age or over, but there is now a warning about this complication in the provider and patient information accompanying the vaccine. The European Medicines Agency (EMA) announced on April 20, 2021 that there may be a link between the J&J/Janssen vaccine and this complication, but that the risk/benefit ratio favors immunization. They are going to ask for a change in the warnings for the vaccine. As of April 23, 2021, there have been 15 cases reported in the United States, all of which occurred in women between the ages of 18-59, with symptom onset between 6-15 days following vaccination. 

  • With all the press surrounding this complication, it is hard to remember that this is a very rare event, but clinicians need to be aware of possible presenting symptoms, since treatment differs from the usual approach. 
    • VITT is the new termed coined by hematology researchers who are investigating the unusual blood clots and thrombocytopenia that has occurred rarely after the use of adenoviral vector COVID-19 vaccines. The CDC is calling it TTS. 
    • The American Society of Hematology offers key takeaway points from their webinar on this topic. Urgent medical evaluation for VITT is indicated if any of the following develop 4-30 days after vaccination: severe headache, visual changes, abdominal pain, nausea/vomiting, backache, shortness of breath, leg pain or swelling, petechiae or purpura. Initial work-up should include CBC with platelet count and imaging for thrombosis based on symptoms, PF-4 HIT ELISA, fibrinogen, followed by emergent hematology consult. 
  • The following information was provided during the April 23 ACIP meeting: 
  • This analysis of 23 patients following vaccination with the AstraZeneca vaccine reviewed the proposed pathogenesis and offers an algorithm for diagnosis and treatment; the risk after vaccination does not appear to be higher than the background risks in the general population. (NEJM; April 16) 
  • The April 16, 2021 issue of NEJM also contained an editorial on VITT induced by all of the SARS-CoV-2 vaccines and a response from Johnson & Johnson pointing out the results of their clinical trials and ongoing safety assessment and the differences between the two adenoviral vector vaccine. 
  • The CDC held a Clinician Outreach and Communication Activity (COCA) webinar on April 27, which can be viewed here. The take-home message is that this complication is rare. Avoid the Janssen vaccine if there is a history of TTS [e.g., heparin induced thrombocytopenia (HIT)]. Risk factors for are VTE unlikely to be associated with an increased risk of TTS, including pregnancy and oral contraceptive use. Do not stop ASA or anticoagulants before vaccination. Have a high index of suspicion in someone who presents with severe headache, visual changes, abdominal pain, nausea/vomiting, backache, shortness of breath, chest pain, leg pain or swelling 6-13 days after vaccination. Work-up should include CBC with platelet count, imaging as indicated, and a PF-4 HIT ELISA. Do not treat with heparin unless HIT testing is negative. 

The ACIP discussed this issue at their scheduled meeting on June 23. There have been 484 cases reported to VAERS, 323 of which have been confirmed. Rates are highest in males, with the highest incidence in those aged 18-24 where the rate is 219 per million doses, so very rare. Although most have been hospitalized, the overwhelming majority of cases have been mild, treated with NSAIDs or steroids with discharge within 2-4 days. The CDC, along with a number of other national medical societies including the AAP, ACOG, AAFP, ACP, and AHA have recommended the benefits of vaccination far outweigh the risks of vaccine complications and vaccines are strongly encouraged. The ACIP does plan to add a statement on myocarditis in the vaccine facts document. Check here for the slides from the meeting. 

Guillain-Barre Syndrome  

The FDA, through the VAERS reporting system has identified 100 cases of Guillain-Barre (GBS) following 12.5 million doses of the J&J vaccine. This number represents a 3-5-fold increase over the baseline rate. These cases have not been fully investigated yet, and the Advisory Committee on Immunization Practices (ACIP) met on July 22 to discuss their recommendations, but the warning is listed on the updated vaccine information sheet. ( The slides from the ACIP meeting ( are available on their website. Analysis of the data from the Vaccine Safety Datalink system and the VA did not notice a statistical signal for GBS but cases were numerically greater after the J&J vaccine compared to the mRNA vaccines. The European Medicines Agency has also noted the same after the AstraZeneca vaccine and posted a similar warning on that vaccine. The conclusions of the CDC from this July 22 meeting is that benefits of the vaccine continue to outweigh the risks. 

Vaccine safety

  • Using data from the V-safe program, the CDC reviewed preliminary data on over 35,000 women who identified as pregnant after their vaccine. Data on almost 4,000 who participated in the pregnancy registry did not show any safety signals of concern, and outcomes were similar to studies on pregnant women before the pandemic. The CDC now recommends that all pregnant women be vaccinated. 
  • Results of safety monitoring from VAERS and V-safe after one month of vaccinations show over 90% of reactions were non-serious. Anaphylaxis rates (4.5 per million doses) remain in range of other vaccines. Female gender may be a risk factor for adverse reactions and anaphylaxis. (MMWR, February 26, 2021
  • A January 27, 2021 update from ACIP shows 50 cases of anaphylaxis following administration of the Pfizer BioNTech vaccine, after 10 million doses (5 per million) and 21 cases following administration of the Moderna vaccine (2.8 per million). 
  • There have now been reports of 196 deaths temporally associated with vaccination, 113 after Pfizer and 83 after Moderna; 66% were residents of long-term care facilities (LTCFs). Estimates of background mortality in LTCFs indicate an expected 11,440 deaths following vaccination. Mortality, then, was actually lower for vaccinated residents. 
  • Bottom line: This vaccine is very safe, and severe allergic reactions are exceedingly rare.