45 CFR 46 Subpart D (Additional Protections for Children in Research)

45 CFR 46 Subpart D is the section of the Common Rule (§§46.401-46.409) that governs federally conducted or funded research involving children, sorting studies into four IRB risk categories and requiring parental permission plus the child’s own assent where the IRB finds the child capable.

Who Counts as a “Child” Under Subpart D

Section 46.402 defines “children” as persons who have not attained the legal age for consent to the treatments or procedures involved in the research, under the applicable law of the jurisdiction in which the research will be conducted. This is a legal-capacity test, not a fixed numeric age — the age of majority (and the age at which a minor can independently consent to specific procedures, e.g. certain reproductive or mental-health services in some states) varies by jurisdiction, so the same protocol can trigger Subpart D in one state and not another for subjects of the same chronological age.

The Four Risk Categories (§§46.404-46.407)

Every Subpart D protocol must be classified by the IRB into one of four categories before approval. The categories are cumulative gates, not alternatives the investigator picks — the IRB determines which one the protocol actually falls into based on risk and benefit profile, and each has its own required findings.

• §46.404 — No greater than minimal risk. The IRB may approve the research if it finds no greater than minimal risk to children is presented, and adequate provisions are made for soliciting child assent and parental/guardian permission under §46.408.
• §46.405 — Greater than minimal risk, with prospect of direct benefit. Permitted if the IRB finds the risk is justified by the anticipated benefit to the subjects, and the risk/benefit ratio is at least as favorable as that of available alternative approaches (e.g. a pediatric oncology trial testing an investigational therapy in children who have the disease).
• §46.406 — Greater than minimal risk, no prospect of direct benefit, but likely to yield generalizable knowledge. Requires four IRB findings: (1) the risk represents only a minor increase over minimal risk; (2) the intervention presents experiences reasonably commensurate with the subjects’ actual or expected medical, dental, psychological, social, or educational situations; (3) the research is likely to yield generalizable knowledge about the subjects’ disorder or condition that is of vital importance for understanding or ameliorating it; and (4) adequate provision is made for assent and permission under §46.408. A pediatric pharmacokinetic sub-study with no therapeutic intent is a typical §46.406 case.
• §46.407 — Not otherwise approvable, but presenting an opportunity to address a serious problem. A narrow escape valve: research that doesn’t satisfy 404-406 can still proceed only if the HHS Secretary, after consulting a panel of experts and providing an opportunity for public review and comment, determines the research presents a reasonable opportunity to further the understanding, prevention, or alleviation of a serious problem affecting the health or welfare of children, and will be conducted per sound ethical principles with §46.408 assent/permission requirements satisfied. This pathway is rarely invoked precisely because it requires Secretarial-level, public review.

Parental Permission and Child Assent (§46.408)

§46.408 requires the IRB to determine that adequate provisions are made for soliciting the assent of children, whenever the IRB judges the children capable of providing it — assent is the child’s own affirmative agreement to participate; a child’s silence or failure to object is not assent. Separately, the IRB must determine what parental/guardian permission is required:

• For §46.404 or §46.405 research, the IRB may find that the permission of one parent is sufficient.
• For §46.406 or §46.407 research, both parents must generally give permission, unless one parent is deceased, unknown, incompetent, or not reasonably available, or when only one parent has legal responsibility for the child’s care and custody.

The IRB can waive some or all assent requirements in narrow circumstances (e.g. the capability of some or all of the children is so limited that they cannot reasonably be consulted, or the intervention holds out a prospect of direct benefit important to the children’s health/well-being that is available only in the research context) — but it cannot waive parental permission on the same terms it can waive general adult informed consent, since Subpart D’s dual-consent structure is the population-specific protection the subpart exists to enforce.

Wards of the State (§46.409)

Children who are wards of the state or any other agency, institution, or entity get an additional layer of protection when enrolled in §46.406 or §46.407 research: such research must either relate specifically to their status as wards, or be conducted in schools, camps, hospitals, institutions, or similar settings in which the majority of children involved are not wards. When wards are included, the IRB must require appointment of an advocate for each child, in addition to any other individual representing the child, who is not associated with the research, the investigator, or the guardian organization.

Relationship to FDA-Regulated Research

FDA-regulated clinical investigations of drugs, biologics, and devices in pediatric subjects apply a structurally parallel set of protections at 21 CFR Part 50, Subpart D (“Additional Safeguards for Children in Clinical Investigations,” §§50.51-50.56), which largely mirrors the four HHS risk categories and the parental-permission/assent structure. A single pediatric trial subject to both a Common Rule agency’s funding and FDA oversight must satisfy both subparts; they are not interchangeable citations for the same requirement.

2024 Technical Update

HHS finalized a rule (Federal Register document 2024-24399), effective October 24, 2024, that amended Subparts B, C, and D of 45 CFR 46 for technical and conforming alignment with the 2018-revised Common Rule — updating cross-references and transition-provision language. HHS’s own characterization is that this update made no substantive change to which populations each subpart covers or to the underlying protections described above.

Frequently Asked Questions

Does Subpart D apply only to federally funded research?

By its own terms, Subpart D binds HHS-conducted or HHS-funded research. In practice its reach is much broader: institutions that hold a Federalwide Assurance (FWA) with OHRP commonly extend Common Rule protections, including Subpart D, to all human-subjects research they conduct regardless of funding source, and many non-HHS federal agencies have separately adopted the Common Rule (including Subpart D) for their own funded research.

Is child assent always required?

No. Assent is required only where the IRB judges the children capable of providing it, considering factors like age, maturity, and psychological state; the IRB can also waive assent under the limited conditions in §46.408(a), such as when a direct-benefit intervention is available only in the research context.

What is the difference between “minimal risk” and “minor increase over minimal risk”?

“Minimal risk” (defined at §46.102) is the baseline used across the whole Common Rule: risk no greater than that ordinarily encountered in daily life or during routine physical/psychological exams. “Minor increase over minimal risk” is a Subpart D-specific, higher threshold used only in the §46.406 finding, permitting a modest step above that baseline when the other three §46.406 findings are also met.

See also: Vulnerable Populations in Research, which situates Subpart D alongside Subparts B and C and the general §46.111(b) IRB safeguard criterion; OHRP (Office for Human Research Protections), the HHS office that administers and interprets the Common Rule including Subpart D; and the Informed Consent vs. Assent comparison for how the two concepts differ in practice.