As respiratory virus season nears and fall vaccination drives get underway, more than half of US children are facing uncertainty over access to this year’s COVID-19 shot. The Centers for Disease Control and Prevention has unexpectedly delayed the distribution of the shots to a key federal program and some states.

Usually, the CDC would allow states to order the newly available seasonal COVID-19 vaccines through the federal Vaccine for Children (VFC) program, which provides vaccines at no cost to children who are uninsured, underinsured, Medicaid-eligible, or Indigenous people in the US. Approximately 52 percent of all US children are eligible for vaccines through the program.

Additionally, The Guardian reports that at least 11 states and one US territory are part of a universal vaccine purchase program, in which they buy all vaccines for children—regardless of their ability to pay or insurance status—through contracts otherwise for the VFC. The 11 states and one territory include: Alaska, Connecticut, Hawaii, Maine, Massachusetts, New Hampshire, New Mexico, Rhode Island, Vermont, Washington, Wyoming, and American Samoan.

“The delay in VFC means delays in these states’ ability to get vaccine for all children,” Demetre Daskalakis, former director of the CDC’s National Center for Immunization and Respiratory Diseases and chief medical officer at Callen-Lorde Community Health Center, told The Guardian.

Kennedy’s track record

In a statement, the Department of Health and Human Services told Ars Technica that “CDC has not yet finalized procurement decisions for COVID-19 vaccines through the Vaccines for Children and Section 317 programs.” The department—currently run by ardent anti-vaccine activist Robert F. Kennedy Jr.—declined to answer the question of why there was a delay in the decision. But the statement suggested that Trump officials were questioning whether children should get the vaccine.

“HHS and CDC are committed to … ensuring that vaccines purchased through federally funded programs are appropriate for the populations those programs serve,” the department said in the statement. It added that additional information about the decision will be released “soon.”

The unexplained delay fits with Kennedy’s well-established disdain for COVID-19 vaccines, which he has falsely called “the deadliest vaccine[s] ever made,” and has actively tried to blame them for the deaths of children, despite no evidence to support the allegations.