Several insurers report that about 80 percent of those who signed up for health insurance on the Affordable Care Act (ACA) marketplaces have made their initial premium payments, but they add that there are "many duplicate enrollments" among the 8 million the Obama administration claims enrolled by the deadline.

The duplicates arose when people frustrated at the site's many glitches sought again and again to sign up.

"It may be months before insurers know how many people activated their coverage by paying their share of premiums," observed Mark Pratt, a senior vice president for America's Health Insurance Plans, an industry trade group.

The enrollment-payment figures were released Tuesday on the eve of a House of Representatives hearing on the Affordable Care Act.

Aetna, which sold plans in 17 states, says of the 600,000 who signed up with the company, "roughly 500,000" have paid so far.