(AP Photo/Reed Saxon)

Health insurers have reported strong sales of individual health coverage outside of the public exchange system for the first quarter, according to analysts at the Henry J. Kaiser Family Foundation.

The analysts estimate that roughly 3 to 3.5 million people signed up for off-exchange coverage that began by the end of March.

That could bring the total number of people insured by individual and family plans to about 15 million, Kaiser analysts said.

Based on the analysts’ analysis, the number of people with individual coverage in effect at the end of March was about 29 percent higher than at the end of December.

Roughly one fourth of this growth was from new plans, including new insurers and CO-OP plans as well as insurers that had previously operated in other markets or states, the analysts said.

“This first look at the direction of enrollment suggests that, even accounting for people leaving the market, the number of people purchasing their own health coverage grew substantially and likely continued to grow toward the end of the enrollment period,” the Kaiser analysts reported.

Health carriers said they were providing individual major medical coverage for 11.3 million people in 2012, and the latest U.S. Census Bureau figures show that 19.4 million people said they had either individual major medical coverage or some other form of individual health insurance, such as a short-term health insurance policy, in 2012, according to an analyst at Mark Farrah Associates.

The Kaiser analysts used Mark Farrah data in their report, but they did not have access to 2013 or 2014 Census Bureau data or complete 2013 or first-quarter carrier enrollment filing data.

The Patient Protection and Affordable Care Act (PPPACA) now requires health insurers to sell coverage to individuals on a guaranteed-issue basis during annual open enrollment periods. Insurers cannot consider health status when enrolling consumers outside the open enrollment periods, but the applicants must show they qualify for “special enrollment periods” (SEPs).

See also: ‘Special’ health sales a mystery.

The Kaiser analysts studied off-exchange open enrollment period activity by looking at carrier reports to state regulators. The number of individual plan sales could be much higher, because filings only represent the number of people whose coverage began by March 31, the analysts said.

Some larger carriers haven’t yet filed their 2014 data, the analysts noted.

“Assuming the off-exchange market experienced a surge similar to the state marketplaces,” the net increase in individual market enrollment could ultimately be twice as large, once the next round of data becomes available, the analysts said.

However, in its report the analysts acknowledged that “many questions remain and we will need to wait for the next round of filings to get a more complete picture of overall enrollment, including capturing the late March enrollment surge.”

The administration said 8.1 million people have signed up for coverage through PPACA’s exchanges as of April.

Allison Bell contributed to this report.