For the majority of vaccine reactions, the vaccine can still be administered in graded doses, according to John Kelso, MD, from the UC San Diego School of Medicine.

John Kelso

"All anaphylactic reactions to vaccines should be evaluated in an attempt to determine the culprit allergen," but do not simply avoid giving the vaccine, he said during his presentation on the vaccine research frontlines at the American College of Allergy, Asthma & Immunology 2020 Annual Scientific Meeting.

It might be tempting to simply label the patient as "allergic to the vaccine," but that "may leave the patient inadequately immunized," he said.

It's best to investigate the allergy with available resources and following allergy investigation procedures, said Kelso.

If the patient has had a previous reaction to a vaccine and has a reaction immediately after receiving the vaccine, do a skin-prick test or an invitro lgE test of the vaccine and its components, Kelso recommended.

All ingredients in every vaccine are listed in the vaccine excipient summary appendix of the Pinkbook, which is published by the Centers for Disease Control and Prevention.

And an online compilation of excipients in vaccines per 0.5mL dose, from the John Hopkins Bloomberg School of Public Health, breaks down vaccines by component, and lists the excipients and allergens, alphabetically, including the amount per dose.

If the test is negative and additional doses of the vaccine are required, administer the vaccine as indicated. If the test is positive and additional doses of the vaccine are needed, they can be administered in graded doses.

The same procedure is recommended if a patient has a clinical history of allergy to gelatin, latex, or yeast, which are common ingredients in vaccines.

"Although there are possibilities of false positives, a 1to 100 dilution for the intradermal test has been shown to be nonirritating," Kelso reported. What's more, "it's important to note that there are no reports of patients who have had intradermal skin tests and have gone on to have a reaction."

If the patient has a reaction to the vaccine, but not immediately, usually no allergy workup needed. In almost all such cases, the vaccine can be administered, on the recommended schedule, in graded doses at 15minute intervals, under observation, he said. If a physician is reluctant to give additional doses, a lab test can be done to measure the patient's lgG antibodies to see if they are protected.

"Most influenza vaccines are literally grown in egg," Kelso said, and "they contain a residual amount of egg protein, or ovalbumin."

However, this has been thoroughly studied with injectable influenza vaccine and intranasal influenza vaccine, live and attenuated, and reactions are rare.

In 27 studies of inactivated vaccine administered to more than 4100 children, including those who have had anaphylactic reactions to egg, there were no reactions, he reported. And published reports describe 1129 children with egg allergy who received live attenuated intranasal flu vaccine, with no immediate systemic reactions.

"It turns out there's just not enough egg protein present to cause a reaction even in the most severely egg allergic patient," Kelso explained. The maximum amount of ovalbumin is less than 1g per 0.5mL dose of influenza vaccine, and amounts measured in independent laboratories are usually much lower than the amounts claimed.

"It is not necessary to inquire about egg allergy before the administration of any influenza vaccine, including on screening forms," according to the Recommendations for Prevention and Control of Influenza in Children, 20202021, issued recently by the American Academy of Pediatrics.

This is one of three main changes in vaccine administration that clinicians "may wish to make" in practice, Kelso said.

The second is that clinicians should be aware that Tdap, a vaccine for tetanus diphtheria and pertussis, can be given regardless of when a previous Tdvaccination was given. Limb swelling, which occurs in 2% to 3% of people after four or five doses, is not a contraindication to the vaccine, he explained.

And the third is that pregnant women can receive injectable (inactivated) influenza vaccine and Tdap, but not live vaccines.

Lisa Saiman

Social media focuses predominantly on negative experiences, which "are easier to perceive than the positive benefits of vaccination: the absence of disease," Lisa Saiman, MD, from the Columbia University Irving Medical Center in New York City, pointed out during her presentation.

The result is a cognitive bias against vaccination, "a disbelief of vaccine efficacy, and a mistrust in pharmaceutical companies and, of course, government," she said.

"But there is a spectrum of vaccine hesitancy and refusal," Saiman said. And there are several resources that physicians can use to explain the importance of vaccines to those who fall into the "cautious acceptor" and "fence sitter" categories, which will help providers maximize the number of patients they vaccinate.

Saiman recommends that providers use talking points from the Countering Vaccine Hesitancy clinical report to guide discussions with parents who are worried about vaccines.

Regular courses of immunization need to be followed, she emphasized. "During the COVID-19 pandemic, measles vaccination rates have declined," and we "clearly are at increased risk of future outbreaks."

"We need to provide catch-up vaccinations expeditiously, and pediatricians must communicate the effectiveness and safety of all vaccines," she stressed.

Kelso and Saiman have disclosed no relevant financial relationships.

American College of Allergy, Asthma & Immunology (ACAAI) 2020 Annual Scientific Meeting: Presented November3, 2020.

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Most Vaccines Can Be Give Safely, Even After Reactions - Medscape