Why is thimerosal in vaccines

The amendment gave the FDA two years to "compile a list of drugs and foods that contain intentionally introduced mercury compounds and At the time the FDA Modernization Act was passed, infants were recommended to receive three different vaccines that contained thimerosal — diphtheria-tetanus-acellular pertussis DTaP , hepatitis B and Haemophilus influenzae type b Hib. Infants receiving all of these vaccines could have been exposed to a cumulative dose of mercury as high as Thimerosal, as a preservative, is no longer contained in any childhood vaccine, with the exception of the influenza vaccine.

One gram is the weight of one-fifth of a teaspoon of water. Despite concerns, several studies have now proven that thimerosal in vaccines did not cause autism:. First, like cystic fibrosis or sickle-cell disease, autism has a genetic basis. Researchers found that when one identical twin had autism, the chance that the other twin had autism was about 90 percent; for fraternal twins, the chance was less than 10 percent.

Second, although autism has a genetic basis, environmental factors can also cause the disease. For example, children whose mothers took thalidomide, a medication that used to be prescribed for nausea during pregnancy, had birth defects, including malformed ears and shortened limbs. But they also had a significantly greater incidence of autism than babies born to mothers who never took thalidomide.

Thalidomide clearly caused autism, but only if mothers took it early in pregnancy. If mothers took thalidomide in the second or third trimester of pregnancy, their babies weren't at increased risk of autism. The thalidomide experience showed that there was a vulnerable time early in pregnancy when a drug could possibly cause autism.

Echoes of the thalidomide story are found in babies infected with rubella virus. Babies born to mothers who suffered rubella early in their pregnancies develop birth defects involving the eyes, ears, brain and heart. They also are at greater risk of developing autism, but like thalidomide, only if the baby is exposed to rubella early during pregnancy. Babies don't develop autism if they are infected with the virus soon after birth.

These findings suggest that a virus or a drug can cause autism, and that there is a vulnerable time early during pregnancy when the baby is at risk. However, during the second or third trimester of pregnancy, or after the child is born, the window for environmental factors causing autism has apparently closed.

Women in the United States also occasionally received mercury when they were pregnant. It happened when doctors found that the mother's blood type was not compatible with their baby's blood type. However, consistent with the observation in Iraq, babies exposed to thimerosal in RhoGAM did not have a greater risk for autism than babies whose mothers never received RhoGAM. Although thalidomide and rubella virus can cause autism in pregnancy, scientific evidence clearly indicates that mercury doesn't.

Read more about autism and vaccines. Prevalence and characteristics of autism spectrum disorder among children aged 8 years—Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, MMWR ;65 3 Surveillance showed the ASD prevalence rate for children 8 years of age in which means they were born after thimerosal removal from childhood vaccines in was The prevalence of autism continues to rise despite the removal of thimerosal from childhood vaccinations.

A 9-year prospective birth cohort study in Poland. European Journal of Pediatrics ; The authors prospectively investigated the relationship between early exposure to thimerosal-containing vaccines and cognitive development in children during the first nine years of life by evaluating children who were vaccinated between birth and 6 months of age with hepatitis B and DTP vaccines using formulations with or without thimerosal.

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. 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 ; Simon et al. 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. FDA has actively addressed the issue of thimerosal as a preservative in vaccines.

The use of thimerosal as a preservative in U. Conducted in , this review found no evidence of harm from the use of thimerosal as a vaccine preservative, other than local hypersensitivity reactions Ball et al.

At the time of this review in , the maximum cumulative exposure to mercury from vaccines in the recommended childhood immunization schedule was within acceptable limits for the methylmercury exposure guidelines set by FDA, the Agency for Toxic Substances and Disease Registry, and the World Health Organization.

However, depending on the vaccine formulations used and the weight of the infant, some infants could have been exposed to cumulative levels of mercury during the first six months of life that exceeded Environmental Protection Agency EPA recommended guidelines for safe intake of methylmercury.

On July 1, , the FDA sent a letter to all licensed manufacturers of vaccines requesting their plans to remove thimerosal from U. Much progress has been made in removing or reducing thimerosal in vaccines. All vaccines routinely recommended for children 6 years of age and younger in the U.

In addition, vaccines that do not contain thimerosal as a preservative are available for adolescents and adults. No Link between Thimerosal in Vaccines and Autism. Although all vaccines routinely recommended for children 6 years of age and younger in the U. There is a robust body of peer-reviewed, scientific studies conducted in the United States and countries around the world that support the safety of thimerosal-containing vaccines.

The scientific evidence collected over the past 15 years does not show any evidence of harm, including serious neurodevelopmental disorders, from use of thimerosal in vaccines. Specifically, the Institute of Medicine now known as the National Academy of Medicine , and others have concluded that the evidence favors rejection of a link between thimerosal and autism. Scientific studies of the risk of other serious neurodevelopmental disorders have failed to support a causal link with thimerosal.

As with pediatric vaccines, vaccines for adolescents and adults are available in formulations that do not contain thimerosal. Note- one vaccine, Tetanus and Diphtheria Toxoids Adsorbed, single-dose presentation, manufactured by Mass Biologics utilizes thimerosal as part of its manufacturing process, not as a preservative, and a trace remains in the final presentation.

FDA-approved seasonal influenza vaccines are available in single-dose presentations that do not contain thimerosal as a preservative for use in infants, children, adults, the elderly and pregnant women.

Vaccines with trace amounts of thimerosal contain 1 microgram or less of mercury per dose. Title 21 of the Code of Federal Regulations, Part An assessment of thimerosal use in childhood vaccines. Pediatrics ; Reliable Sources of Immunization Information. Evidence Shows Vaccines Unrelated to Autism. View All Handouts for Vaccine Confidence. Ask the Experts: Vaccine Safety. VISs are information sheets produced by CDC that explain both the benefits and risks of a vaccine to vaccine recipients.

Vaccine Basics: Vaccine Safety. The Vaccine Basics gateway page on vaccineinformation. Understanding Thimerosal, Mercury, and Vaccine Safety. Timeline: Thimerosal in Vaccines Timeline shows key activities of government agencies concerning thimerosal in vaccines from to Listing of studies, including description, study design, publication date, and objective.

Information about thimerosal and summary of studies that show no link between thimerosal in vaccines and autism. Thimerosal: What You Should Know. Thimerosal and Vaccines. Vaccine Safety: Examine the Evidence. List and links to articles that show there is no link between vaccines and autism. Vaccine Ingredients: Is there mercury in vaccines? Easy-to-understand explanation of ingredients included in vaccines.

Vaccine Research: Thimerosal and Autism. The National Academy of Medicine, formerly known as the Institute of Medicine IOM , is an impartial group of the world's leading experts that advises Congress on science issues. Fact sheet provides key facts, overview, safety, and WHO response.

Thiomersal and Vaccines. Thimerosal in Vaccines. Straight talk about why parents don't need to worry about mercury in childhood vaccines. Countless studies have shown no link between vaccines and an increased risk of autism spectrum disorder. Video FAQs: Is there mercury thimerosal in vaccines? Vaccine Questions? IAC in the News. IAC History through Film. Repository of Resources. Hep B Birth Dose. MenB Vaccination for Colleges. Subscribe to IAC Express. Needle Tips Archive. Vaccinate Adults Archive.

Vaccinate Women Archive. DVD Immunization Techniques. Thimerosal does not stay in the body a long time so it does not build up and reach harmful levels. When thimerosal enters the body, it breaks down to ethylmercury and thiosalicylate, which are readily eliminated. Thimerosal use in medical products has a record of being very safe.

Data from many studies show no evidence of harm caused by the low doses of thimerosal in vaccines. The most common side-effects are minor reactions like redness and swelling at the injection site. Although rare, some people may be allergic to thimerosal. Research does not show any link between thimerosal in vaccines and autism , a neurodevelopmental disorder. Many well conducted studies have concluded that thimerosal in vaccines does not contribute to the development of autism.

Even after thimerosal was removed from almost all childhood vaccines, autism rates continued to increase, which is the opposite of what would be expected if thimerosal caused autism.

Measles, mumps, and rubella MMR vaccines do not and never did contain thimerosal. Varicella chickenpox , inactivated polio IPV , and pneumococcal conjugate vaccines have also never contained thimerosal. Influenza flu vaccines are currently available in both thimerosal-containing for multi-dose vaccine vials and thimerosal-free versions.