2012 Vaccine revenue: $4.11 billion

Pfizer ($PFE) continues to stand tall on the enormous success of its pneumococcal conjugate vaccine Prevnar 13, the world's best-selling vaccine. The product is approved in 120 countries and continues to nab expansions. In 2012 sales of the product hit $3.72 billion, up from $3.66 billion in 2011. Analysts anticipate revenue to hit a whopping $6.75 billion by 2018. If so, it would remain the best-selling vaccine and outsell the next-best-selling vaccine, Sanofi's ($SNY) PENTAct-HIB, by more than 3 to 1.

With such a leg to stand on, Pfizer has some wiggle room when it comes to developing new products. In December the company sold a vaccine to protect against meningitis, sepsis and pneumonia to startup Nuron Biotech for an undisclosed amount. And the company is now racing against GlaxoSmithKline ($GSK) and NovaDigm Therapeutics to come up with a vaccine to stop methicillin-resistant Staphylococcus aureus (MRSA), which kills more people in the United States than skin cancer. Two other companies failed to make an effective vaccine of this kind--most recently Merck ($MRK) in 2011. Pfizer has two candidates in early trials.

For more:
FDA expands use of Pfizer's Prevnar 13
Pfizer's Prevenar 13 gets shot in arm with WHO approval
Nuron acquires Pfizer's meningitis vaccine

-- Alison Bryant