What animals eggs are used in vaccines and does this then affect your immune system causing allergies to eggs

The short version: chicken eggs are used to grow influenza vaccines, but the evidence shows the tiny leftover egg protein does not cause allergic reactions in egg-allergic people.

The only animal eggs used in vaccine production are chicken eggs, specifically for influenza vaccines. The flu virus is grown in fertilized chicken eggs, then killed and purified [1, 16]. Trace amounts of egg protein (ovalbumin) can remain in the final shot, typically less than 1 microgram per dose [18]. Some newer flu vaccines are made in insect or mammal cells instead of eggs, which avoids egg protein entirely [16].

The evidence on whether this causes egg allergies is actually quite clear, and it goes against what many doctors were taught. A review of 28 studies covering 4,315 egg-allergic people (656 with a history of anaphylaxis to egg) found zero serious allergic reactions to egg-based flu vaccines [18]. A separate study gave the live nasal flu vaccine to 68 egg-allergic children and saw no immediate allergic reactions at all [17]. The ovalbumin dose in vaccines is far below the amount known to trigger reactions in even highly allergic people [18].

The old practice of skin-testing or splitting the dose into fractions has been abandoned because it was unnecessary. The risk is not zero in theory, but in practice it is so low that major guidelines now say egg allergy is not a reason to skip or delay flu vaccination [18]. If you are still worried, cell-culture or recombinant flu vaccines contain no egg protein at all [16].

My call: chicken eggs are the only animal eggs used in vaccines, and the evidence shows the trace egg protein does not cause allergic reactions in egg-allergic people. Confidence: high.