while looking at info about re-infections, found this interesting article
Moriah Bergwerk, etc Covid-19 Breakthrough Infections in Vaccinated Health Care Workers. New England Journal of Medicine, July 2021 reporting on 1500 vaccinated health care workers. Here are interesting tidbits: 2.5% (40 cases) of them got infected (Covid-alpha) in 14 weeks. Of these, 1/3- no symptoms, 2/3 – mild.
Likely source of infection – 100% unvaccinated persons (60% – household member, 30% – other healthcare worker or patient: 7 out of 11 from just one patient)
Most who got infection had low antibody levels – thus antibody level can serve as a marker of risk (contrary to “asinine” CDC recommendation not to do these tests)