All-cause pneumonia hospitalizations per 100,000 US adults, 3a. Annual rates, 1997–2009; 3b. Average annual rates, 1997–1999, 2001–2006, 2007–2009; the year of 7-valent pneumococcal conjugate vaccine (PCV7) introduction, 2000 is not included. * p<.05 for rate decline from pre-PCV7 years; +p<.05 for rate increase from pre-PCV7 years