There are some statistical concerns with how Israel came up with their numbers, so I would put more faith in other countries results, at least for now. My best guess is that the 64% is for any detectable disease, not symptoms (i.e. you test positive but don't feel meaningfully different), which means the vaccines do their job at quickly eliminating the virus.
The more important result is although Delta is resistant to being neutralized by existing antibodies, it does not prevent it in serum-trials against vaccinated individuals, the like most biological systems the human immune system is exponential: starting from an effective antibody response, it can overwhelm any nascent infection (i.e. hospitalizations would not be expected to rise).
The number I've seen is a 3-5 fold reduction in the kinetics of neutralization [1] - this is concerning for whether you can spread it, but seems to my eye pretty consistent with hospitalization effectiveness remaining about the same.
Maybe. But I was commenting on the real hospitalization numbers and implied vaccine protection from comparing the ratios 1) hospitilized vaccinated vs hospitilized non-vaccinated [the linked spear sheet] and 2) vaccinated in relevant age brackets vs non-vaccinated in relevant age brackets.
