Passage: Alternative medicine proponents gain from promoting vaccine conspiracy theories through the sale of ineffective and expensive medications, supplements, and procedures such as chelation therapy and hyperbaric oxygen therapy, sold as able to cure the 'damage' caused by vaccines. Homeopaths in particular gain through the promotion of water injections or 'nosodes' that they allege have a 'natural' vaccine-like effect. Additional bodies with a vested interest in promoting the "unsafeness" of vaccines may include lawyers and legal groups organizing court cases and class action lawsuits against vaccine providers. Conversely, alternative medicine providers have accused the vaccine industry of misrepresenting the safety and effectiveness of vaccines, covering up and suppressing information, and influencing health policy decisions for financial gain.In the late 20th century, vaccines were a product with low profit margins, and the number of companies involved in vaccine manufacture declined. In addition to low profits and liability risks, manufacturers complained about low prices paid for vaccines by the CDC and other US government agencies. In the early 21st century, the vaccine market greatly improved with the approval of the vaccine Prevnar, along with a small number of other high-priced blockbuster vaccines, such as Gardasil and Pediarix, which each had sales revenues of over $1 billion in 2008.

Question: What happened to the vaccine market when Prevnar was approved by the CDC?
greatly improved