WASHINGTON — Seven states have yet to participate in a federal program to buy antivirals for a potential influenza pandemic. Thirteen states do not have adequate plans to distribute vaccines and medical supplies from the Strategic National Stockpile.

Those findings and others are part of a new report on how well states have prepared for public health emergencies. The report concluded that states have made significant progress since the terrorist and anthrax attacks in 2001. However, critical gaps remain.

Seven states performed adequately in each of the 10 categories that were measured, which earned them a score of 10 from the Trust for America's Health, a research group. The top scores went to Illinois, Kentucky, Nebraska, New Jersey, Pennsylvania, Tennessee and Virginia.

The states that got the lowest score were Arkansas, Iowa, Mississippi, Nevada, Wisconsin and Wyoming.

The federal government has had a difficult time measuring progress when it comes to the billions of dollars it has sent states over the past six years to improve preparedness. The money went to upgrade laboratories, buy medical supplies and conduct training exercises.

The Bush administration has encouraged states to stock up on antivirals in the event of an influenza pandemic. Under one program, the federal government will pay for a quarter of the cost of buying Tamiflu or Relenza, and states pay the remainder for a combined investment of about $680 million.

Antivirals reduce the severity of influenza.

Seven states have so far declined to purchase any antivirals, according to the report: Colorado, Connecticut, Florida, Massachusetts, Mississippi, North Dakota and Rhode Island. Several more have bought only a fraction of what they're entitled to under the federal program.

"States that are not buying the full amount of antivirals we have allocated under this program are putting their own citizen at risk," said HHS Spokesman Bill Hall.

Pennsylvania has purchased 75 percent of its share of antiviral drugs available from the federal government to stockpile in case of a flu pandemic, according to the trust. Pennsylvania also just met the minimum threshold of enlisting sufficient volunteers for a "medical reserve corps" of doctors and other health-care professionals in case of a pandemic — 14 per 100,000 people.

It is among 43 states that can conduct lab tests during emergencies involving bioterrorism or infectious disease, and its lab can be staffed around the clock to analyze samples from bioterrorist attacks, natural disasters, or disease outbreaks, the trust said.