I thought you might be interested in the Medical Research Council's current guidance on research involving children.
1. Research should only include children where the relevant knowledge cannot by obtained by research in adults.
2. The purpose of the research is to obtain knowledge relevant to the health, wellbeing or healthcare needs of children.
3. Researchers can only involve competent children if they have obtained their informed consent beforehand.
4. A child's refusal to participate or continue in research should always be respected.
5. If a child becomes upset by a procedure, researchers must accept this as a valid refusal.
6. Researchers should involve parents/guardians in the decision to participate wherever possible, and in all cases where the child is not yet competent.
7. Researchers should attempt to avoid any pressures that might lead the child to volunteer for research or that might lead parents to volunteer their children, in the expectation of direct benefit (whether therapeutic or financial).
8. Research involves partnership with the child and/or family, who should be kept informed and consent to separate stages of the project. Obtaining consent is a continuing process, rather than a one-off occurrence. Children and their families are likely to appreciate some recognition of their role in this partnership, such as a certificate of participation.
9. Researchers must take account of the cumulative medical, emotional, social and psychological consequences of the child being involved in research. Children with certain conditions may be exposed to a sequence of research projects. It is advisable to consider the risks of a particular research procedure in the context of the child's overall involvement in projects by different researchers.
Well, there you are. And if your response in the "covid" context is a sentence beginning, "Ah, but ..." forget it.