The Federal government was not at issue in Jacobson. The challenge was to the authority of the State of Massachusetts to enact a vaccination requirement. The court held that public health requirements are an element of "police powers", and since those are not specifically reserved to the federal government by the Constitution, they are powers of the state....and therefore the requirement was legal.
I think it could be argued that since Jacobson held that the vaccination is a power of the state, it
cannot be a broad power of the federal government. In other words, the President can't enact a requirement that all US citizens/residents be vaccinated.
However...the Federal government
can regulate interstate commerce - although to what extent is up for debate - so that creates some authority to impose working standards. They can also make vaccination a condition of employment, contracting, or funding (which they're doing), and that action covers an awful lot of workers. OSHA is also charged with protecting employees from hazards, including health hazards, and has authority to impose protections as well.
Problem I see with the OSHA approach is that there's no precedent I'm aware of for OSHA-mandated vaccination. The only vaccination I can think of in their worker standards are the hepatitis vaccine for people exposed to bloodborne pathogens, but workers are allowed to opt out of it - and don't have to provide any reason to do so. There are some worker settings where there are additional protections, but OSHA rules rely on preventing exposure, rather than on vaccination. The only way I can see this rule sticking requires that:
- COVID be defined as a "grave danger" in the workplace. Based on precedent, they'll need to state (and support how they determined) that workers will be exposed in the workplace and will die as a direct result of that exposure without the rule.
- They'll have to explain why COVID is more dangerous than hepatitis, measles, flu, MRSA, tuberculosis, Ebola, and every other contagious illness that we don't have mandatory vaccination for.
- They'll have to indicate - and support - how their rule will prevent the exposures and deaths mentioned in #1. They'll also have to show that those exposures and deaths can't reasonably be prevented using other methods.
The rule will be issued and will go into effect before it's challenged, but I see very little likelihood of it standing up to challenge. Most of OSHA's previous emergency rules have failed in the courts, including one about asbestos protections.
Bottom line, I think the OSHA path fails. While tying Federal funding to vaccination goes a long way, ultimately state requirements would be the most effective way to implement a mandate.