An executive order signed by Donald Trump with little fanfare on Friday could have a huge impact on the health of US children, as it instructs the Centers for Disease Control and Prevention (CDC) to cut the number of recommended childhood vaccines almost in half.

The vague language of the order, which refers to “a scientific assessment that compared United States childhood immunization recommendations with those of peer nations” published in January by anti-vaccine activist Robert F Kennedy’s health and human services department, does not explicitly state that the new recommendation removes vaccines against seven diseases from the schedule.

The assessment, co-authored by the subsequently fired vaccine skeptic Dr Tracy Beth Høeg, concluded that the CDC director should update the childhood immunization schedule “to keep vaccines for 10 diseases – measles, mumps, rubella, polio, pertussis, tetanus, diphtheria, Haemophilus influenzae type B (Hib), pneumococcal disease, and human papillomavirus (HPV) – for which peer, developed nations share international consensus, as well as varicella (chickenpox) … in the category of vaccines recommended for all children”.

Implementing that recommendation would mean removing vaccines for these diseases from the recommended schedule:

• hepatitis A

• hepatitis B

• meningitis

• rotavirus

• influenza

• Covid-19

The assessment also recommended cutting the number of doses of the human papillomavirus, or HPV, vaccine from two or three (depending on the child’s age) to one.

The order directs the CDC and its Advisory Committee on Immunization Practices (ACIP) to review the HHS assessment and clinical data to update the vaccine schedule for children and adolescents.

“It is the policy of the United States that the core childhood vaccine schedule should be aligned with scientific evidence and best practices from peer, developed countries while preserving access to vaccines currently available to Americans,” the White House said.

Fifteen states with Democratic governors are suing the HHS and Robert F Kennedy Jr over the administration’s proposed changes to the federal vaccine recommendations, arguing that stripping “vaccines of their universally recommended status, in favor of senseless complexity and equivocation that will make children sicker and strain state resources”. The suit also complained of a CDC memo downgrading the recommendation for a vaccine against respiratory syncytial virus, or RSV.

“There seems to be little scientific basis for altering the recommendations that have gone through,” Dr William Schaffner, a professor of medicine at the Vanderbilt University school of medicine and a former member of ACIP, told the Association of American Medical Colleges in January.

“If we do not progressively vaccinate children from certain diseases, sooner or later we will see the resurgence of these diseases, just as we are seeing with recent outbreaks of measles,” Schaffner added. “The consequences of that will be more sick children, more visits to the doctor and more hospitalizations.”

The lawsuit from the states also noted that the health department assessment supposedly aligning the US vaccine schedule with those “peer countries” had “a particular focus on Denmark”.

“But Denmark is not a ‘peer country’ in relation to vaccines because, among other things, unlike the US, it has a small, homogenous population and universal healthcare,” attorneys for the 15 states argued. “And Denmark’s vaccine policies are a global outlier that cannot be retrofitted to the US.”

“Even Danish health officials are baffled by Defendants’ reliance on Denmark,” the attorneys added, referring to comments to the New York Times from an official at Denmark’s equivalent of the CDC.

“It’s not at all fair to say look at Denmark unless you can match the other characteristics of Denmark,” the Danish official, Dr Anders Hviid, told the Times in December.

In that interview, Hviid also noted the irony in Kennedy’s health department relying on Denmark, given that he and other Danish health officials had debunked Kennedy’s theories of vaccine harm.

Reuters contributed reporting