If an assembly or class of assemblies pose a significant threat to public safety, then it does not violate the right to peaceable assembly for government to limit or prohibit them (if the targeting is discriminatory on religious or other content grounds, there may be issues with religious freedom or free speech aspects of the first amendment, but that's not an issue here.)

That's why the right to peaceably assemble doesn't mean you can, e.g., freely blockade hospital entrances. Public health quarantines have been recognized as a legitimate state power by the US Supreme Court consistently, in cases running back to 1824 (Gibbons v. Ogden.)