Are vaccines containing mercury safe?
Are vaccines containing mercury safe? A Chinese doctor shared his experience with a person: Some time ago, an old gentleman came to the clinic to get the flu vaccine and asked me if the vaccine contains no mercury. If it contains mercury, he would not take it. Before calling, he repeatedly confirmed that it contains no mercury. The doctor took out the instructions and he saw that it did not contain mercury, and he was relieved to get the vaccine. This is the first person in the clinic who cares about whether the vaccine contains mercury.
Why is mercury added to the vaccine?
Vaccines are a kind of preparation injected into the human body, and prevention of microbial contamination is a necessary safety requirement. The mercury added to the vaccine is called thimerosal, also called thimerosal sodium thiosalicylate, which is a broad-spectrum bacteriostatic agent, which has strong inhibitory ability against gram-positive bacteria, gram-negative bacteria and fungi. The purpose of the vaccine is to prevent potential contamination of harmful microorganisms, just as the purpose of adding antibiotics such as gentamicin and neomycin to the vaccine is the same.
Is mercury in vaccines harmful to humans?
Organic mercury is divided into methyl mercury and ethyl mercury, and methyl mercury is a neurotoxin. When thimerosal enters the human body, it is decomposed into ethyl mercury and sodium thiosalicylate. Although the two brothers of ethyl mercury and methyl mercury are only one word difference, the harm is far different. Ethyl mercury can enter the intestines actively and does not accumulate in the human body. It can be quickly converted into inorganic mercury. The toxicity of inorganic mercury to the brain is significantly less than that of ethyl mercury and methyl mercury, and it is excreted faster. Therefore, thimerosal does not produce any other reactions other than allergies to the human body.
Large doses of thimerosal can cause neurological and renal toxicity, and the content of thimerosal in vaccines is very, very low. The danger of small doses of thimerosal is mainly to cause allergic reactions.
After decades of close monitoring by the WHO Global Vaccine Safety Advisory Committee, it is believed that there is no evidence that infants, children or adults will experience mercury poisoning after being vaccinated with a vaccine containing thimerosal. Except for mild skin allergic reactions, there is no evidence of immunization. The adverse reactions can be attributed to thimerosal.
Before each vaccine is marketed, the State Drug Administration of China will strictly examine and approve the safety of the vaccine, including the vaccine strain and all the excipients. Only after it is qualified can it be marketed for vaccination. If thimerosal is harmful to the human body, the country will definitely not approve the listing.
With the improvement of living standards, people are becoming more and more concerned about mercury and other toxic heavy metals. In early November, the State Drug Administration issued a notice: from January 1, 2026, the production of mercury-containing thermometers and mercury-containing sphygmomanometers is prohibited.
Although there is no evidence that the thimerosal in vaccines has obvious harm to the human body, the American Academy of Pediatrics and the Public Health Agency issued a joint statement on thimerosal in July 1999, advocating the removal or reduction of thimerosal as a preservative in vaccines as soon as possible.
Since 2001, the US FDA no longer approves new vaccines containing thimerosal. Except for some formulas of influenza vaccines, vaccines for children recommended by the US CDC contain no or only trace amounts of thimerosal.
The 2015 edition of the Chinese Pharmacopoeia also requires preservatives, especially mercury-containing preservatives, to be avoided as much as possible in the intermediate and finished products of pharmaceuticals. In the future, there will be fewer and fewer mercury-containing vaccines. We also expect more and more “green vaccines” to be available on the market, so that parents can vaccinate their children with more confidence.
There is no problem with the safety of all vaccines on the market in China. If there is no contraindication to vaccination, vaccination according to regulations is the best way to prevent the corresponding infectious diseases.