Vaccines
Work in Progress Updated Feb 6, 2026
Background
Skin Testing
Management
| Reaction Type | Perform Skin Testing? | Vaccine Administration by Skin Testing Result (if applicable) |
|---|---|---|
| Delayed reaction (e.g. late-onset urticaria, local arm swelling) | No | Subsequent dose in usual manner |
| Immediate reaction without IgE-mediated reaction features (e.g. tingling, flushing, palpitation, sensation of throat closure) | No | Subsequent dose in usual manner but observe for 30 minutes |
| Immediate reaction with IgE-mediated reaction features (e.g. urticaria, angioedema, wheezing) | Yes | Negative: Usual manner 30 min obs Positive: Split dose |
| Anaphylaxis | Yes | Negative: Split dose Positive: Graded dose |
| Step | Volume (mL) of full-dose full-strength for 0.5 mL vaccine dose | Dilution | Percent of full-dose full-strength for 0.5 mL vaccine dose | Observation |
|---|---|---|---|---|
| 1 | 0.05 | Full-strength | 10% | 30 minutes |
| 2 | 0.45 | Full-strength | 90% | 30 minutes |
| Step | Volume (mL) | Dilution | Percent of full-dose full-strength | Observation |
|---|---|---|---|---|
| 1 | 0.05 | 1:10 | N/A | 15 minutes |
| 2 | 0.05 | Full-strength | 10% | 15 minutes |
| 3 | 0.1 | Full-strength | 20% | 15 minutes |
| 4 | 0.15 | Full-strength | 30% | 15 minutes |
| 5 | 0.2 | Full-strength | 40% | 15 minutes |
Vaccine components There are exceedingly rare reports of patients who have had allergic reactions to vaccines due to excipients, such as neomycin, thimerosal, latex, milk, and yeast. However, most of these allergies are quite rare and the overwhelming majority of patients with allergy to any of these substances tolerate vaccines containing them uneventfully, again likely due to an insufficient amount of the allergen being present in the vaccine to provoke a reaction.2 Thus, vaccine or excipient skin testing before the administration of vaccines containing these excipients in patients with reported allergic reactions to them is not required, and the vaccines can be administered in the usual manner (Fig 1). However, in patients who have already had an immediate allergic reaction to a vaccine containing one of these excipients, skin testing or serum-specific IgE testing for the constituent may be warranted.
The only exception to this general rule that almost all patients tolerate vaccines that contain substances to which they are allergic is gelatin. A number of vaccines contain milligram quantities of gelatin (Table 2), and most of the anaphylactic reactions reported to these vaccines have been determined to be due to IgE directed against the gelatin they contain.
Gelatin also contains alpha-gal and patients with alpha-gal syndrome may also be at risk for reactions to gelatin-containing vaccines
gelatin, alpha-gal - Varicella, MMR, MMRV, Rabies vaccine
latex - vaccines with rubber latex in syringes, vials, diluents, caps or packaging; which is becoming less common –> The “rubber” in vaccine vial stoppers or syringe plungers may be either dry natural rubber (DNR) latex or synthetic rubber. Those made with latex pose a theoretical risk to latex-allergic patients, either as a result of liquid vaccine solution extracting latex allergens from the stopper by physical contact or by passing the needle through the stopper and retaining latex allergen in or on the needle. –> patients with anaphylaxis to latex can safely receive vaccines from vials with non-DNR stoppers. If the only available preparation has a latex stopper, if possible, the stopper should be removed and the vaccine drawn up directly from the vial without passing the needle through the stopper [49]. If the only available vaccine contains latex in the packaging that cannot be avoided, such as in a prefilled syringe, the vaccine can still be administered, but the patient should be observed for at least 30 minutes afterward.
egg - yellow fever vaccines –> The only other vaccine containing egg protein is yellow fever vaccine. Although yellow fever vaccine may contain a somewhat higher quantity of ovalbumin,13,14 as with influenza vaccine, the amount of ovalbumin may not be sufficient to provoke a reaction even in patients with egg allergy. The package insert for yellow fever vaccine contains a protocol for the evaluation of recipients with egg allergy.15 It is recommended that patients with egg allergy undergo prick skin testing with the vaccine full-strength, and if the result is negative, undergo intradermal testing with the vaccine diluted 1:100. For patients with negative vaccine skin test results, it is recommended that the vaccine be administered in a single dose under observation. For patients with positive vaccine skin test results, it is recommended that the vaccine be administered in graded doses under observation (Table 1). Most patients with egg allergy have negative yellow fever vaccine skin test results and receive the vaccine in a single dose uneventfully.16,17
neomycin,streptomycin, polymyxn B - large local reaction; positive patch testing
vaccine allergy https://www.sciencedirect.com/science/article/pii/S1081120622000497 - Current guidelines conclude that patients with egg allergy are not at increased risk for reaction to egg-based influenza vaccines. There is no need to ask about egg allergy before the administration of influenza vaccines, including on screening forms. - Except for gelatin, most patients with allergy to vaccine constituents tolerate vaccines containing them.
Resources
resources: Sources of information — A list of potential allergens contained in vaccines is maintained by the Institute for Vaccine Safety and is available online [22]. https://www.uptodate.com/external-redirect?target_url=https%3A%2F%2Fwww.vaccinesafety.edu%2Fdo-vaccine-ingredients-cause-adverse-events%2F&token=7WXHlGY7nCwSOVn3SwCiCLqmo9fdfPpuy9fTeCLUgixroJT2bH3tIqdkft9pf%2FRop%2Fipz%2FKNwWF%2FHrO1fODcTovxZjM4CK84pNTuNC55hKg%3D&TOPIC_ID=2074
In addition, the Centers for Disease Control and Prevention (CDC) provides tables of excipients contained in vaccines, categorized by vaccine [23]. https://www.uptodate.com/external-redirect?target_url=https%3A%2F%2Fwww.fda.gov%2Fvaccines-blood-biologics%2Fvaccines%2Fvaccines-licensed-use-united-states&token=wCcUPYLTKXZ5S1UGXUKfKr94oxDQyONzYC1uFsK%2BYnQ2%2B4KaGLMcoHHsAbP1LWfZN0ygLpycExSlzNHyAzL3GOlOTh%2B%2BOgpb44BnyQIFSrI%3D&TOPIC_ID=2074
references: stone immune-mediated ADRs https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bcp.14112