The problem is that this may not be temporary. Even if a democrat is elected next time or a pro-vaccine health secretary appointed, reversing previous policies may not happen. Cutting funding for treatment of foreign children is much easier than switching it back on. Any subsequent administration will probably prioritise domestic policies over foreign aid. Even if democrats win both houses and the presidency, there still may be attempts at legislative blocks.Kennedy Withdraws U.S. Funding Pledge to International Vaccine Agency
Full story at the New York Times. (Article wasn't paywalled for me. Your mileage may vary.)
If Europe switches up military spending then their ability to compensate for cuts in US aid will be limited. China (and India?), may become more dominant.
