The anti-vaccine movement gained momentum more than a decade ago with the publication of a study (with 12 children) showing an association between the MMR vaccine and autism. Since then, the paper has been retracted (and its senior author discredited) because of data manipulation, and a dozen of large-scale studies (a recent one included more than 90.000 children) have conclusively shown that there is no link between the vaccine and autism. Nevertheless, the anti-vaxxers persist with a series of arguments for which there is no scientific evidence but that generate hesitancy among an increasing number of affluent and educated people who, due to the success of vaccination itself, have forgotten that not so long ago children were dying from diseases such as diphtheria, polio or measles.
1. “Vaccines contain toxic sustances such as aluminium and mercury”
In a normal day, we breathe, eat or drink 30-50 mg of aluminum, more than 20 times the maximum allowed dose in a vaccineAdjuvants are sometimes necessary to boost the immune response and decrease the dose of inactivated virus or bacteria in the vaccine. Aluminum salts are not the most effective adjuvant but have been used as such for more than 80 years and in thousands of millions of doses precisely because of their safety. In a normal day, we breathe, eat or drink 30-50 mg of aluminum, more than 20 times the maximum allowed dose in a vaccine (0.85 mg).
Thimerosal is a preservative that inhibits the growth of potentially lethal bacteria or fungi. It is metabolized into ethyl mercury (which is less toxic and eliminated more rapidly) and not methyl mercury (as anti-vaxxers claim). In 2001, thimerosal was taken out of childhood vaccines while other vaccines, with the exception of the influenza shot, contain only trace amounts. Even then, we are exposed to higher amounts of mercury (69 mcg) when eating one can of white tuna (180g) than with one dose of influenza vaccine (25 mcg maximum).
Formaldehyde is part of the vaccine manufacturing process and is present at residual quantities in the final product. Our body contains higher doses of circulating formaldehyde at any time than that contained in any vaccine. In fact, there is more formaldehyde in an apple than in the Hepatitis B, DTaP and polio vaccines together.
2. “Too many vaccines can overload the child’s immune system”
Children are exposed to a greater amount of environmental antigens in one single day than those contained in all the vaccines they receiveFrom the moment we are born, we are continuously exposed to a huge amount of virus and bacteria. Fortunately, our immune system is prepared to recognize and combat an almost unlimited number and diversity of antigens (protein fragments derived from any organism and capable of inducing an immune response). Children are exposed to a greater amount of environmental antigens in one single day than those contained in all the vaccines they receive, combined. In addition, the bacteria and virus within vaccines are inactivated.
3. “Natural immunity is better”
Indeed, for certain pathogens, naturally acquired immunity may last longer than that acquired through vaccination. However, the risk associated to a natural infection is not comparable to the risks associated to any vaccine. For example, measles causes 2 deaths out of 1000 infected individuals in developed countries (in low-resource countries the number can be up to 20 times higher), whereas the MMR vaccine causes one severe adverse reaction in one out of 1 million vaccinated individuals. The benefits of vaccinating largely outweigh the risks.
4. “Vaccines cause autoimmune disorders, asthma and allergies”
Not one single large-scale study has showed that vaccines increase the risk of autoimmune disroders or allergies Not one single large-scale study has showed that vaccines increase the risk of autoimmune disorders or allergies. MMR vaccination has been associated to cases of idiopathic trombocytopenia, an autoimmune disorder. However, several studies agree that the frequency of such disease in vaccinated children (1 in 30,000) is much lower than that observed in children that contract rubella (1 in 3,000) or measles (1 in 6,000). Likewise, two large scale studies conclude that there is no evidence for the supposed association between the Hepatitis B vaccine and multiple sclerosis that was reported in France between 1991 and 1997. Such vaccine has been used in more than 500 million people and is considered one of the safest vaccines yet developed.
It is true that the prevalence of asthma, allergies and autoimmune diseases is increasing, particularly in developed countries. But there is accumulating evidence that this phenomenon is due to the “hygienic” environment in which we live wherein we are exposed to less bacteria and parasites, particularly at an early age, and we are modifying our gut flora – whose diversity is key in maintaining a functional and “well-behaved” immune system – through an excessive use of antibiotics and the consumption of high-fat, low-fiber diets.
Admittedly, new parents have the right to question the risks and benefits of vaccinating their children. The scientific community has the obligation to listen and provide them with clear and transparent information. And we, as a society, have the responsibility of refusing any type of fanatism that denies scientific evidence, no matter how loudly they shout.
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