Nonetheless, the us states of Iowa and California passed legislations in favour of mercury-free vaccines. The uproar was not restricted to the us: the Danish parliament, in 1992, banned the heavy metal from vaccines. The uk has recently passed a similar legislation. At the root of the problem is thimerosal: this preservative with a 50 per cent mercury constituent is a key ingredient of multi-dose vaccines. These vials are about 10 times cheaper than single-dose vials, making it easier for international agencies to procure vaccines for programmes in developing countries including India. In 2000, for instance, about 80 per cent of vaccines administered globally were supplied in multi-dose vials.
But these vials require preservatives because they are used over longer periods. Thimerosal fits this requirement. So, it’s not surprising that international bodies such as the World Health Organization (who) and unicef recommend this preservative. Even those vaccine manufacturers based in developed countries who make mercury-free vaccines for domestic consumption use this heavy metal in their products for developing countries.
What are the implications?
Most vaccines used for the country’s universal immunisation programme (uip) have a thimerosal content of 25 µg per five millilitres. Half of that, 12.5 µg, is mercury. A six-week old infant in many parts of the country is administered two vaccines, dpt ( diphtheria, pertussis and tetanus ) and Hepatitis b. T his exposes the child to 25 µg of mercury. Infants getting vaccinated at a private clinic are also administered the haemophilus influenza type b vaccine, as per the Indian Academy of Paediatricians’ protocol. This results in a total exposure of 37.5 µg. According to the us Environment Protection Agency, the human body can, in a day, safely tolerate 0.1 µg of mercury for every kg of its body weight. So, an average six-week infant, weighing 7 kg, can tolerate an exposure of 0.7 µg of mercury. The child is exposed to mercury levels much higher than this recommended amount on innoculation day.
The risk of mercury is even higher for the undernourished — and underweight — Indian children. At a who meet of the Global Advisory Committee on Vaccine Safety in 2003, it was pointed out that little is known of susceptibility to thimerosal in infants who weigh less than 2.5 kg. Moreover, children are less equipped to handle the toxic load because they do not produce sufficient levels of bile, needed to remove mercury from the body.
However, many experts contend that ethyl mercury used in vaccines is not as toxic as methyl mercury, commonly blamed for maladies such as the Minamata disease. But there are others who dispute this argument.
Dubious methods
Thimerosal was developed in the 1930s by the us- based vaccine major, El Lilly and Company. For years the company has manipulated studies to demonstrate the safety of this mercury-based preservative. In fact, when thimerosal was introduced, the company did have it tested, but only on 22 patients with terminal meningitis. And quite conveniently meningitis was blamed for the death of all those injected with the preservative.
More recently, Eli Lilly used the us government’s paranoia against bio-terrorism to its advantage. Along with other vaccine companies, it persuaded the us government to introduce a clause in the Homeland Security Act — brought in response to the 9/11 attacks — stipulating that these companies can be challenged only in vaccine courts, and not in civil courts. Anxious to ensure vaccine supplies against any anthrax or smallpox attacks, the us government complied.
