Only about a third of seniors were vaccinated in 2008 against pneumonia, a complication of seasonal flu, according to the report released by the Trust For America's Health, the Infectious Diseases Society of America and the Robert Wood Johnson Foundation.

Merck and Co makes a vaccine called Pneumovax to protect adults against Streptococcus pneumoniae infections, which cause pneumonia and a range of other illnesses. But U.S. health officials say only about a quarter of adults who should get it ever do.

Children are protected against seven strains of S. pneumoniae bacteria with Pfizer Inc's Prevnar.

Overall, adult vaccination rates are particularly low for minority groups, according to the report.

Sixty-nine percent of older whites received the seasonal flu vaccine in 2008, compared to 53 percent of older African Americans and 51 percent of older Hispanics, the report found.

Only 36 percent of all adults were vaccinated against the seasonal flu in 2008 and only about 2 percent of adults had tetanus, diphtheria, and whooping cough vaccines, the report found.

Limited health insurance coverage, high out-of-pocket costs and limited access are major reasons adults skip vaccinations, but misinformation is also an obstacle, the report said.

Despite the evidence of safety and effectiveness of vaccines, many adults are unaware that they need certain vaccinations or are misinformed about vaccines, the report said.

Millions of American adults go without routine vaccinations every year, leading to as many as 50,000 preventable deaths and thousands of preventable diseases, the report said.

Pneumococcal disease alone kills more than 1.6 million people worldwide each year, including 800,000 children.

Diseases that can be prevented by vaccines add an estimated $10 billion a year to U.S. healthcare costs, according to the U.S. Centers for Disease Control and Prevention.

The immunization report says adults need vaccinations for new diseases and booster shots for diseases they were vaccinated against as children, because the immunity may wane over time.

(Editing by Eric Beech)