As stockpiles of government-purchased vaccines ran out, insurance companies began picking up the cost for Americans insured under public plans such as Medicare, and under most private plans as well. These costs are being borne by insurers, and it's likely those costs will be shifted to consumers and purchasers in some way, even if there isn't an up-front charge for booster shots.

 The new strain

The most recent COVID strain to gain attention is the EG.5 variant, which has been nicknamed "Eris." In August, the World Health Organization (WHO) classified Eris as a "variant of interest," which means that health officials should monitor the spread of this strain because of mutations that might make it more contagious or severe.

Eris is now the dominant strain in the U.S., according to the Centers for Disease Control and Prevention, although there remains a lack of data on the strain, due to its relatively recent detection.

The good news is that Eris does not seem to be causing more significant illness than earlier strains, officials said. "While EG.5 has shown increased prevalence, growth advantage, and immune escape properties, there have been no reported changes in disease severity to date," said the WHO.

The vaccine boosters coming in the fall should also be helpful in preventing infection with this strain and limiting its severity, even though its newness means that the boosters aren't specifically targeted to Eris. According to a report in Prevention.com. "The updated COVID vaccine will target XBB.1.5, which is a subvariant of Omicron and is similar to EG.5 (a.k.a. "Eris," also a subvariant of Omicron), said Richard Watkins, M.D., an infectious disease physician and professor of medicine at the Northeast Ohio Medical University. In other words, the boosters that will be available this fall have been updated to fight subvariants of Omicron that have been dominant since last year."

Employer-based plans should cover booster shots

According to an analysis by the Kaiser Family Foundation (KFF), booster shots will most likely be covered as a preventive service, just as initial vaccine shots are required to be covered by the ACA.

"Most people with health insurance will still be able to get COVID-19 vaccines, including boosters, for free even after the federally purchased supplies are depleted," the report said. "In addition, … there is also the cost of vaccine administration which could range from about $25 to $40 per dose, as well as a potential physician visit fee. For insured people, these costs would be covered by the insurer, as they are currently."

The U.S. Department of Health and Human Services also indicates that vaccines, including boosters, will continue to be covered: "Most forms of private health insurance, including all Affordable Care Act-compliant plans, must continue to cover without cost-sharing COVID-19 vaccines furnished by an in-network health care provider," the HHS website said. "People with private health insurance may need to pay part of the cost if an out-of-network provider vaccinates them."

Related: HHS awards $1.4B in grants for future vaccines, antibody

The KFF report also noted that the uninsured may face some new costs for boosters. "While most consumers with public and private insurance will be protected from having to pay directly for vaccine costs, those who are uninsured and underinsured may face cost barriers when the federally purchased vaccine doses are depleted. In addition, as private payers take on more of the cost of vaccinations and boosters, this could have a small upward effect on health insurance premiums."