First off, please read this information from the FDA website :

Rationale for Preservatives in Vaccines

Preservatives may be defined as compounds that kill or prevent the growth of microorganisms, particularly bacteria and fungi. They are used in vaccines to prevent microbial growth in the event that the vaccine is accidentally contaminated, as might occur with repeated puncture of multi-dose vials with a needle . In some cases, preservatives are added during the manufacturing process to prevent microbial growth. However, improvements in manufacturing technology have markedly decreased the need to add preservatives during the manufacturing process.

The United States Code of Federal Regulations (the CFR) requires, in general, the addition of a preservative to multi-dose vials of vaccines; and, worldwide, preservatives are routinely added to multi-dose vials of vaccine. Tragic consequences have followed the use of multi-dose vials that did not contain a preservative and have served as the impetus for this requirement. One particularly telling incident from Australia is described by Sir Graham S. Wilson in his classic book, The Hazards of Immunization.

In January 1928, in the early stages of an immunization campaign against diphtheria, Dr. Ewing George Thomson, Medical Officer of Health of Bundaberg, began the injection of children with toxin-antitoxin mixture. The material was taken from an India-rubber-capped bottle containing 10 mL of TAM. On the 17th, 20th, 21, and 24th January, Dr. Thomson injected subcutaneously a total of 21 children without ill effect. On the 27th an additional 21 children were injected. Of these children: eleven died on the 28th and one on the 29th. (Wilson 1967)

This incident was investigated by a Royal Commission and the final sentence in the summary of their findings reads as follows: The consideration of all possible evidence concerning the deaths at Bundeberg points to the injection of living staphylococci as the cause of the fatalities.

From this experience, the Royal Commission recommended that biological products in which the growth of a pathogenic organism is possible should not be issued in containers for repeated use unless there is a sufficient concentration of antiseptic (preservative) to inhibit bacterial growth.

The U.S. requirement for preservatives in multi-dose vaccines was incorporated into the CFR in January 1968, although many biological products had contained preservatives, including thimerosal, prior to this date.

The risk of contamination of vaccines cannot be completely eliminated even with the use of preservatives. The literature contains several reports of bacterial contamination of vaccines despite the presence of a preservative, emphasizing the need for meticulous attention to technique in withdrawing vaccines from multi-dose vials. (Bernier et al 1981; Simon et al. 1993). The need for preservatives in multi-dose vials of vaccines is nonetheless clear.

It is important to note that the FDA does not license a particular preservative; rather, the FDA evaluates safety and effectiveness data for the vaccine containing the preservative and makes a determination whether to issue a license for the vaccine.

Thus, according to the FDA, the sole purpose of vaccine preservatives is to enable doctors to use the same vaccine container repeatedly.

The repetitive use of the same vaccine container is a bio-hazard and should absolutely not be allowed; every vaccination should be from a fresh container, otherwise a serious health risk occurs due to contamination.

There is ABSOLUTELY NO NEED FOR PRESERVATIVES. The injection of preservatives is ABSOLUTELY IRRATIONAL.

If there are additional reasons neglected by the FDA that necessitate the requirement for preservatives in vaccines I certainly look forward to hearing about them.