Thank you for your inquiry.
Yes, there is concern regarding the potential for gelatin to cause allergic reactions in patients receiving varicella vaccine. Below you will see a quote taken directly from the CDC website. See the link to the website to read further about this.
In addition, the reference noted below from the Journal of Allergy and Clinical Immunology in 1997 also reports reactions to gelatin in varicella vaccine.
Thank you again for your inquiry and we hope this response is helpful to you.
"People should not get chickenpox vaccine if they have ever had a life-threatening allergic reaction to a previous dose of chickenpox vaccine or to gelatin or the antibiotic neomycin."
IgE-mediated systemic reactions to gelatin included in the varicella vaccine
Masahiro Sakaguchi, Tatsuru Yamanaka, Kazuo Ikeda, Yasuko Sano, Hiroyuki Fujita, Takuma Miura, Sakae Inouye et al. J Allergy Clin Immunol 1997 (February); 99(2):263-264.
Phil Lieberman, M.D.