I wonder if an ideal vaccine would mimic natural infection. A natural infection grows and grows and grows until the immune system finally gets going and snuffs if out, over the course of days or weeks.
Perhaps a slow-release vaccine would work better than a multi dose regimen? Two or three huge doses doesn’t really mimic anything like what an infection actually looks like.
There's always a balancing act between vaccine safety and efficacy. The smallpox vaccine mimics a natural infection, but it's extremely dangerous because people who get vaccinated can actually spread real smallpox to others for a period of time, so they have to stay isolated.
Pre-Covid coronavirus vaccines tested in animals induced antibody-dependent enhancement and were thus deemed unsafe for human trials. A safe, effective Covid vaccine was always a long shot. Maybe one day we'll get one, but maybe we won't. Thankfully, there are multiple other drugs that are effective at preventing and treating Covid.
Perhaps a slow-release vaccine would work better than a multi dose regimen? Two or three huge doses doesn’t really mimic anything like what an infection actually looks like.