After several delays, Pfizer Inc. ( PFE ) received the much awaited approval from the US Food and Drug Administration (FDA) for its 13-valent pneumococcal conjugate vaccine, Prevnar 13. The vaccine is meant to prevent the invasive disease such as sepsis, bloodstream infections and meningitis, caused by 13 Streptococcus pneumoniae in infants and children of 6 weeks – 5 years of age. Prevnar 13, to be administered in four dosages at 2, 4, 6 and 12-15 months, is a new version of the currently available pneumococcal vaccine, Prevnar, one of the best selling vaccines worldwide. While Prevnar treats illness caused by 7 strains of pneumococcal bacteria, the new vaccine is expected to block 13 strains including the original 7. In another positive development, a panel of experts from the US Centers for Disease Control and Prevention (CDC) recommended Prevnar 13 to be administered to children between 2 – 59 months of age. It is estimated that Prevnar 13 would cover 92% of the invasive pneumococcal disease, compared to 81% covered by Prevnar. The US approval is based on data from 13 phase III studies carried out on more than 7,000 children. Pfizer has agreed to conduct certain post-marketing studies to further evaluate the safety profile of the vaccine, the prevention of overall invasive pneumococcal disease and reduction of ear infection. In addition to the US, Prevnar 13 is approved in 38 countries. The vaccine is also being studied in adults with the regulatory submission expected in 2010. Prevnar was added to Pfizer’s portfolio following its $67 billion acquisition of Wyeth which enabled it to diversify into vaccines and biotechnology medicines. Pfizer has been depending on Wyeth’s portfolio to help offset patent expirations, especially its highest selling drug Lipitor, which is slated to lose patent exclusivity in 2011. Read the full analyst report on "PFE" Zacks Investment Research