Vaccines are one of the biggest successes of modern medicine. They save up to 3 million people worldwide every year. From research and discovery to product development, it can cost up to a billion dollars to make one vaccine, and that process — can last up to 15 years. During the past few decades the number of companies producing vaccines has dwindled to just a handful. The four big drug companies that now dominate the market are Merck, Pfizer, Sanofi Pasteur and GlaxoSmithKline.