[Brown University School of Public Health dean Dr. Ashish] Jha said he is troubled by the fact that young, healthy people would get so-called breakthrough infections within a few months of vaccination. Scientists expected ["]protection["] to wane over time, and they expected the vaccines to be less effective among older people and those with pre-existing health conditions. But that's not who got sick in this study.
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The good news is none of the 39 [Israeli] people who got infected passed the coronavirus on to anyone else, according to the study, published Wednesday in the New England Journal of Medicine.

He said current vaccines are great at preventing serious infection deep in the lungs, but not at blocking infection in the upper airways [cranial olfactory bulb "blood-brain barrier"]. What's needed, he said, is a nasal-spray vaccine that would stop the coronavirus from taking hold at all.
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The study followed about 1,500 Israeli health care workers for four months after they received the Pfizer-BioNTech vaccine. Anyone who tested positive more than 11 days after the second dose was considered a breakthrough case.

Most had the alpha variant of the virus, which is more contagious than the original version [?], but less infectious than the delta variant that now accounts for most cases in the United States.