Bergwerk, Gonen, and colleagues identified 39 breakthrough infections of SARS-CoV-2 among 1497 healthcare workers who had been fully vaccinated with the Pfizer–BioNTech (BNT162b2 messenger RNA) vaccine. The majority (85%) of isolates from these infections were the B.1.1.7 alpha variant, which was the most widespread variant circulating in Israel at the time of the study. Healthcare workers who were symptomatic and/or had a known exposure were evaluated using multiple diagnostics, including RT-PCR, antigen-detecting RDTs, and serological tests. Investigators matched four or five controls with each of the 22 breakthrough cases for whom the study had peri-infection neutralizing antibody data available. In a comparison of titres during the peri-infection period, the case control analysis revealed lower neutralizing antibody tires among the patients with breakthrough infections compares to the controls (ratio 0.36, 95% CI 0.17, 0.79). Two thirds (67%) of cases had mild symptoms while the other third (33%) were asymptomatic. None of the breakthrough infections required patient hospitalization; however, 19% of cases had prolonged symptoms six weeks of infection.