A preservative called thimerosal has been used in some vaccines since the 1940s. It keeps vaccines from becoming contaminated, which may cause severe reactions, serious illness, or death. Thimerosal has trace amounts of ethylmercury (a type of mercury) and is used to prevent vaccines from getting bacteria or fungi in them. Thimerosal is only necessary as a preservative for some vaccines that come in multi-dose vials, which contain more than one dose of vaccine.
Preservatives are not needed for vaccines in single-dose forms. All vaccines provided by Washington state for children 6 years and under are free of thimerosal as a preservative except for flu vaccine in multi-dose vials. For those who prefer a thimerosal-free flu vaccine, single-dose flu shots and nasal spray vaccines are both available depending on the person's age.
Thimerosal is safe in the doses found in vaccines and is easily eliminated naturally from the body. However, as a precautionary measure, Washington has a law that children under 3 years old and pregnant women cannot receive any vaccine containing more than a trace amount of thimerosal. This law can be suspended by the Washington State Secretary of Health in times of outbreak or vaccine shortage.
There is currently no suspension on these limits since there is no shortage of thimerosal-free flu vaccine. In the event of a suspension, we will post on this webpage a notice for providers to inform the appropriate patients.
What are Washington's legal limits on mercury in vaccines?
Per Washington state law (RCW 70.95M.115), pregnant women and children under 3 years of age should not be given vaccines that contain more than trace amounts of mercury (thimerosal).
Under what conditions can the state's law on mercury limits be suspended?
The law allows the Washington State Secretary of Health to suspend the law's mercury limits to protect the public's health against disease if there is:
- An outbreak of vaccine-preventable disease, OR
- A shortage of vaccine that meets the terms of legal limits on mercury.
What determines a vaccine shortage?
Three basic conditions might cause the Department of Health to declare a vaccine shortage:
- The Centers for Disease Control and Prevention declares a national shortage of a thimerosal-free version of the vaccine.
- The Secretary of Health determines there is a threat to public health due to lack of vaccine availability.
- A local health officer determines a threat to public health within a local health jurisdiction with the need to control or prevent a vaccine-preventable disease outbreak.
Which vaccines do not meet the limitations of the law?
Currently, only the following vaccine has more than trace amounts of thimerosal and is subject to the state law:
- Multi-dose vials of flu vaccines (single-dose flu vaccines are mercury free and available as an alternative)
It is against the law for providers in Washington to vaccinate pregnant women or children under 3 years of age with multi-dose flu vaccines (except in the event of a declared suspension).
How do these limits affect me and my family?
Very few vaccines are now manufactured with more thimerosal than allowed in the Washington law. The law may affect you or your family in the following ways:
- If you are pregnant, you must get a single-dose flu shot instead of a flu shot from a multi-dose vial. Pregnant women are not recommended to receive nasal spray flu vaccine because it is a live vaccine.
- If you have a child under 3 years of age, he or she must get a single-dose flu vaccine instead of a flu shot from a multi-dose vial. Children 2 years and older may receive their flu vaccine as a shot or as nasal spray.
How does the law affect the public purchase of vaccine?
Since 2005, all routinely recommended vaccines provided by the Washington State Department of Health for children from birth through 3 years of age are mercury-free, including single-dose flu vaccine. All vaccines provided by Washington state for children 6 years and under are free of thimerosal except for flu vaccine in multi-dose vials. For those who prefer a thimerosal-free flu vaccine, there are two options: Single-dose flu shots are available for anyone age 6 months and up, and nasal spray vaccine is available for those age 2 through 49 years who are not pregnant.
What should providers do to meet the terms of the law?
- Providers should administer single-dose flu shots for children under 3 years of age and pregnant women.
- Providers should estimate how many patients are pregnant, may become pregnant, or are under 3 years of age and expect to receive a flu vaccination in the coming year to most accurately pre-book their flu vaccine supply.
- During a suspension of mercury limits, providers must notify pregnant or lactating women and parents/legal guardians of anyone under the age of 18 years if they are to receive a vaccine that exceeds the legal limits on mercury outlined in the law. Providers should note that notification requirements in the event of a suspension apply to a larger population than those affected by the current state law on mercury limits.
When have mercury limits been suspended?
There is currently no suspension of these limits in Washington.
A suspension last occurred from October 2010 to June 2013 because the Food and Drug Administration determined that single-dose, pre-filled syringes may contain trace amounts of latex which may cause allergic reactions in latex-sensitive people. The mercury limits were suspended by the Secretary of Health to allow people to get multi-dose flu vaccines. The suspension was lifted after latex-free, thimerosal-free flu vaccines were again available.