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eMJA     The Medical Journal of Australia

Commercial vaccine formulations contain a range of additives or manufacturing residuals, which may contribute to patient concerns about vaccine safety.

Vaccines contain constituents such as preservatives, stabilisers, adjuvants and biological growth media, which may contribute to consumer concern about vaccine safety; specifically:

Antibiotics such as neomycin and polymyxin B are often used to prevent bacterial contamination during vaccine manufacture;5 they may contribute to systemic allergic reactions, including anaphylaxis, or local skin reactions.13 Previous skin reactions to neomycin are not considered a risk factor for anaphylaxis and are not a contraindication for use of neomycin-containing vaccines.13 Neomycin concentrations may vary between vaccines, but most contain only residual amounts.14

Adjuvants are used in vaccine manufacture to enhance immune responses to the vaccine antigen. Aluminium hydroxide and phosphate are commonly used adjuvants, and can augment type 2 (antibody-mediated) immune responses without influencing type 1 (cell-mediated) immune responses, or cytotoxic T cell responses.15 Aluminium adjuvants also induce antigen-specific IgE responses, which may predispose vulnerable individuals to allergic reactions. However, no data were identified associating use of aluminium adjuvants with increased risk of allergy-related events.

The presence of aluminium adjuvants has been associated with injection-site reactions such as nodules, granulomas and erythema.17,18 A systematic review of controlled safety studies reported that vaccines containing aluminium produce more erythema and induration than other vaccines in young children (up to 18 months of age), and greater local pain in older children (10–18 years).19

Gelatin is a partially hydrolysed collagen, usually of bovine or porcine origin, and is one of many types of stabilisers added to vaccines.5 It may be responsible for some allergic reactions occurring after vaccination, with symptoms including urticaria, anaphylaxis, or local reactions.21 “Egg allergies” reported after MMR vaccination were found to occur in individuals with no sensitivity to egg,5 and were later found to represent gelatin sensitivity. However, the incidence of anaphylaxis to gelatin is low (about one case per 2 million doses).5

Egg-related allergy is common, particularly in children with asthma or general allergies, and may be as high as 40% in children with moderate to severe atopic dermatitis.21 The risk of egg-related allergy after vaccination depends on the presence of egg protein in the final product. For example, influenza vaccine is manufactured using the extra-embryonic fluids of chick embryos and contains measurable quantities of egg proteins.21 Although the National Health and Medical Research Council (NHMRC) immunisation guidelines state that “individuals with anaphylactic hypersensitivity to eggs should not be given influenza vaccine”,7 little evidence is available to identify the actual risk of serious allergic reactions in this context.

MMR vaccine is developed using chick embryo fibroblast tissue, and the final commercial vaccine does not contain egg proteins. Egg allergy is not a contraindication;7 previous reports of allergy-related adverse events occurring after MMR vaccination have now been attributed to the presence of gelatin.5

Vaccine manufacture requires the production of organisms cultivated on an appropriate culture medium. A medium must provide nutrients such as proteins, albumin, polypeptides, and growth factors specific to the needs of the microbe. Animal sera are frequently added to culture media to provide nutrients for microbial growth. Bovine serum is primarily used, although serum from pigs, horses, rabbits or humans may also be used.24 Extensive filtering processes ensure that the final vaccine contains little, if any, of the original cell material. Some media are serum-free or may be of synthetic, semi-synthetic or yeast origin.

Some vaccines are manufactured using Saccharomyces cerevisiae (baker’s yeast). There are no reports of yeast-specific IgE detected in patients following exposure to vaccines manufactured using baker’s yeast. Currently, the risk of vaccines contributing to yeast allergy is theoretical.5

Patients may be exposed to latex during vaccination via its presence in syringe plungers and vial stoppers. Latex contains numerous polypeptides, many of which may act as allergens; case reports describe various immediate-type hypersensitivity reactions occurring post-vaccination in patients with a history of latex allergy, including anaphylaxis.39

Website has an incomplete list of ingredients of vaccines which may be of concern to  consumers.

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