Wal-Mart Stores, Inc. (NYSE: WMT), the world's largest retailer, is expanding its immunization offerings in the U.S. to help lift revenue to levels it is achieving outside the U.S.

The Bentonville, Ark.-based company's U.S. health care business is already a significant contributer to revenue -- it accounted for 11 percent of last year's $264 billion in net sales. But Wal-Mart aims to boost that percentage, especially in view of the fact that overseas sales growth far outpaces its domestic sales growth: In the three months ended July 31, U.S. sales rose a mere 3.8 percent compared with a 6.4 percent gain overseas.

Beginning Monday, the company will add flu and pneumonia injections to its currently available lineup of inoculations. Specifically, U.S. customers will be able to get vaccinations for hepatitis A and B, chickenpox, HPV, shingles, MMR (measles, mumps and rubella), meningitis and Tdap (tetanus, diphtheria and pertussis). 

The company didn't say how much the new immunizations will cost. It currently charges $25 for the flu and pneumonia injections. It has contracted Mollen Immunization Clinics of Scottsdale, Ariz., to handle the network of registered nurses that will be deployed to approximately 2,700 store locations from Monday until Nov. 15. 

"Many adults are not up to date with recommended life-saving immunizations. Vaccinations may not be top-of-mind while the weather is still warm, but they are a critical part of public health, especially in light of recent outbreaks of whooping cough and shingles," said John Aqwunobi, M.D., president of Walmart U.S. Health and Wellness and former U.S. assistant secretary for health.

As Aqwunobi's title suggests, Wal-Mart is serious about its efforts to expand into health care services. In 2010, the company launched a successful prescription drug program with Louisville, Ky.-based Humana Inc. (NYSE: HUM) that offers a stand-alone prescription drug plan for people on Medicare. In 2006, it rolled out a generic-drug program.

Not all its efforts to expand into the health care field have been immediate successes. The company failed in its plan to open 2,000 health clinics by this year; it currently considers its 150 clinics a pilot program. When Wal-Mart began soliciting information from health care providers about prospects for primary care services -- such as management of diabetes and HIV infections -- it quickly backed down after the solicitations were made public. Aqwunobi had to issue a clarification that the solicitation letter was "overwritten and incorrect."

Wal-Mart shares fell 21 cents to $71.56.