We are searching data for your request:
Upon completion, a link will appear to access the found materials.
Flu vaccines are supplied in either single- or multi-dose vials.
Each year the Centers for Disease Control and Prevention makes a nationwide push to increase vaccination rates against influenza, a viral respiratory disease that kills approximately 6,000 Americans and sickens many more every winter. Immunization against flu is recommended for everyone over 6 months of age. To meet this annual demand, vaccine manufacturers must begin production several months ahead of each flu season, which typically begins around October in northern latitudes. Influenza vaccines were almost universally packaged in multiple-dose vials until the late 1990s, when public concerns over preservatives forced a change in manufacturing practices.
The Need for a Preservative
All vaccines, including those designed to protect you from influenza, contain biological agents whose shelf lives are limited. Since the 1930s, many vaccine products have been manufactured with thimerosal, a mercury-based preservative that extends vaccine shelf life and reduces the risk for bacterial or fungal contamination. Including thimerosal in vaccines permits manufacturers to store their products before the flu season, and it facilitates the use of multi-dose vials, which reduces the costs of production and saves money for consumers -- or their insurance companies.
Mercury is a naturally occurring metallic element. Even though mercury is widespread in nature, if it builds up in your tissues it can cause irreversible brain and kidney damage. Developing fetuses and growing children are particularly vulnerable to the toxic effects of mercury. One as-yet unsubstantiated but widely disseminated concern is that mercury exposure plays a role in autism. Mercuric compounds are effective antibacterial and antifungal agents, so they were widely used as preservatives until the 1970s, when the dangers of mercury exposure were finally established. It wasn't until 1991 that mercury-based paints were banned, however, and it took another decade to remove thimerosal from most vaccines. Manufacturers' claims that they had no alternative to thimerosal delayed its removal from vaccines. In addition, there was insufficient evidence that thimerosal caused any harm, an issue that was repeatedly examined by the Institute of Medicine during the first decade of the 21st century.
Thimerosal versus Methylmercury
Much of the data regarding mercury toxicity is derived from investigations of methylmercury, which is the most common form of mercury in nature and the most common culprit identified in cases of mercury poisoning. The Environmental Protection Agency, the Food and Drug Administration and the Agency for Toxic Substances and Disease Registry have all established daily limits for methylmercury consumption, and each has established guidelines that incorporate significant margins of safety. According to the FDA, thimerosal does not break down into methylmercury when it is metabolized in the human body. Rather, thimerosal is metabolized to ethylmercury, and a number of studies suggest that ethylmercury may not be as toxic to humans as methylmercury. Thus, the exposure limits established for methylmercury may not apply to ethylmercury. However, no safety standards exist for ethylmercury as of 2013, and this is an issue that is still open to debate.
Current Flu Vaccines
At the end of 2012, more than a dozen different formulations of flu vaccine were available. Many brands -- such as Fluzone, Agriflu, Fluarix and Afluria -- were available as thimerosal-free, single-dose vials. Others, such as Flulaval, were only available as multi-dose vials, and they contained thimerosal to prolong their shelf life and prevent contamination when they were reused. Most manufacturers that supply single-dose, thimerosal-free vaccines also manufacture multi-dose vials containing thimerosal. Fluzone and Afluria, for example, are available in both single- and multi-dose vials. Multi-dose and single-dose preparations of injectable flu vaccines contain killed influenza viruses, so you cannot get the flu from one of these vaccines. Dosages are determined by the age of the person receiving the vaccine. With the exception of their thimerosal content, vaccinations taken from multi-dose vials are equivalent to those found in single-dose vaccines. If you have concerns about thimerosal or questions about which type of vaccine is best for you or a family member, ask your doctor.