The updates to the IHR are even worse than the treaty. And unlike the treaty, there is no legal argument for congress needing to approve the changes since congress already approved the initial regulations years ago.

Best defenses are:

Assertion of religious liberty and the unwavering defense of it to object to further unwanted medical treatments.

Unwillingness for businesses and local magistrates to uphold international rules. This is tough because the federal government and other governments around the world can use a lot more leverage to punish businesses and local regions that do not comply than they even had during covid.

10th amendment being upheld in the courts and the courts recognizing that international treaties may be equally as binding as the constitution but treaty provisions that violate the constitution are void. This point is tricky because there isn't a ton of legal precedent in this area but it is a route I can imagine being taken.

The president withdrawing from the WHO. Least likely scenario. Unless Trump is elected I don't see this happening. RFK jr would alao probably wothdraw but i dont really see him being elected as likely at all. Only reason I think Trump would do it is because he withdrew from the WHO a few months prior to leaving office but first thing Biden did was join again. Then the admin was one that proposed the changes to the IHR that radically reduce national sovereignty. The changes to the IHRare still being ironed out and may not reflect the admin's proposals but it is all being done in secret so we havemo idea where negotiations are at the moment.