WE should be cautious about putting animal blood products into people (MS sufferer's new drug hope, The Press, December 27).

Modern science still cannot guarantee that these animal-derived substances will be free of contaminants that may result in disease or allergies.

The fact that our health authorities still approve such "unsafe" science in the 21st century raises some troubling questions. It was public pressure - and not the Government - that led to a ban on the use of animal-derived polio vaccine in UK babies in the wake of the "mad cow" crisis. The vaccine had been grown in serum from calves. Sadly, some scientists continue to rely on animals as biological factories instead of much safer non-animal methods. There is no reason why medical progress cannot go hand in hand with safer science.

Andre Menache MRCVS, Scientific consultant to Animal Aid, The Old Chapel, Bradford Street, Tonbridge.