The middle of the last century was a boom time for vaccine makers. Many common diseases, especially of childhood, began to resemble a distant memory. Researchers and manufacturers were eyeing up a shopping list of future targets. But then things went wrong. Some diseases proved much more complex. Litigation prompted by real or imagined side effects began to worry the drug companies. Profits started to slide. Many manufactures got out of the business. The best idea ever for preventing disease seemed to be going nowhere. That's now changed. Advances in biotechnology and the advent of a couple of new, commercially successful vaccines have injected a new confidence into the industry. In spite of repeated failures to deal with two of the highest profile diseases, malaria and HIV, vaccine researchers have rewritten their shopping list. This now includes not just the traditional targets - the classic infectious diseases - but even some types of cancer, autoimmune disease and smoking! Geoff Watts reviews past ups and down of vaccine making, and explains why its fortunes have now changed. Examining the enterprise in commercial as well as scientific terms, he investigates whether the commerce and the science of vaccine development are likely to confront new hurdles - or if the future really does offer the prospect of hitherto unattained levels of immunity, a new golden age for vaccines. PRODUCER: Martin Redfern.