A government effort to motivate Medicare patients to seek preventive medicine, by offering such services for free, has only slightly increased the number of older Americans getting cancer tests, key vaccines and other preventive care.

Some 5.5 million Medicare patients have used at least one preventive benefit since Medicare eliminated the charges in January, according to figures released Monday by the Department of Health and Human Services.

And as of early June, nearly 780,000 Medicare patients had an annual checkup, while 16,000 got counseling to quit smoking — two benefits added to the program for the first time. But for services that had been covered in the past, dropping the charges did not produce a large spike in their use, compared with last year, when patients still had to pay for them.

Eliminating co-payments and deductibles for preventive services in Medicare was part of the 2010 law to overhaul the health care system. Obama administration officials have touted the change as a way to improve the health of older Americans and lower spending on their care by catching medical problems early.

On Monday, HHS Secretary Kathleen Sebelius announced that the agency was launching a publicity campaign, known as “Share the News, Share the Health” to alert Medicare patients, their doctors and their relatives that the services are available at no charge. “Our job is to make sure every single Medicare beneficiary in the country knows,” Sebelius said.

Specifically, the figures show that as of early June, one in six patients in the traditional Medicare program had received some kind of preventive service this year. The figures exclude older Americans in private health plans through a part of the program called Medicare Advantage.

Compared with last year, the number of women in Medicare getting mammograms increased by about 150,000 to nearly 2.3 million. There have been similar small increases for bone density tests, screening for colon cancer, Pap tests and pelvic exams. The number getting vaccines against hepatitis B actually fell.