Heavy metal

Vaccines with mercury can cause autism, but removing the metal is uneconomical for developing countries such as India

In the 1980s, worried parents and medical researchers in the US alleged that mercury in vaccines was responsible for the growing number of autism cases among children in the country. The issue was debated in medical circles, wheels moved in many western countries, but developing countries still don’t have a choice — because without mercury, vaccination is expensive.

There was pressure on the US government for legislation against mercury in vaccines. At the same time, a combative vaccine industry brandished studies vouching the safety of mercury in vaccines. 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.

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