Associations between vaccine breakthrough cases and infection by SARS coronavirus 2 (SARS-CoV-2) variants have remained largely unexplored. Here we analyzed SARS-CoV-2 whole-genome sequences and viral loads from 1,373 persons with COVID-19 from the San Francisco Bay Area from February 1 to June 30, 2021, of which 125 (9.1%) were vaccine breakthrough infections. Fully vaccinated were more likely than unvaccinated persons to be infected by variants carrying mutations associated with decreased antibody neutralization (L452R, L452Q, E484K, and/or F490S) (78% versus 48%, p = 1.96e-08), but not by those associated with increased infectivity (L452R and/or N501Y) (85% versus 77%, p = 0.092). Differences in viral loads were non-significant between unvaccinated and fully vaccinated persons overall (p = 0.99) and according to lineage (p = 0.09 - 0.78). Viral loads were significantly higher in symptomatic as compared to asymptomatic vaccine breakthrough cases (p < 0.0001), and symptomatic vaccine breakthrough infections had similar viral loads to unvaccinated infections (p = 0.64). In 5 cases with available longitudinal samples for serologic analyses, vaccine breakthrough infections were found to be associated with low or undetectable neutralizing antibody levels attributable to immunocompromised state or infection by an antibody-resistant lineage. These findings suggest that vaccine breakthrough cases are preferentially caused by circulating antibody-resistant SARS-CoV-2 variants, and that symptomatic breakthrough infections may potentially transmit COVID-19 as efficiently as unvaccinated infections, regardless of the infecting lineage.

We compared the antigenemia assay (AA) with tandem shell vial cultures (SVCs) and tube cultures (TCs) for detection of cytomegalovirus (CMV) in 343 blood specimens. For 249 specimens, the AA was performed in duplicate with two different commercially available monoclonal antibody reagents (Biotest Diagnostic Corporation and Argene Biosoft). Specimens considered true positives were positive in either culture system or both AAs. Only specimens which were negative in both cultures and positive in a single AA were tested retrospectively with a CMV PCR assay. CMV recovery rates were also calculated to determine if increased specimen age resulted in decreased positivity. CMV recovery rates for the AA and the combination of both cultures were 20.0 and 5.0% at 3 to 18 h, 20.2 and 14.0% at 18 to 35 h, 12.5 and 7.8% at 36 to 52 h, and 18.8 and 6.3% at 64 to 75 h, respectively. The sensitivities and specificities of the Biotest AA, the Argene AA, SVC, and TC were 84.4 and 100.0, 100.0 and 99.6, 44.4 and 100.0, and 46.0 and 100.0%, respectively. The AA was significantly more sensitive than either culture method alone and was also more sensitive than the two culture methods used in tandem (the tandem culture sensitivity was 63.5%); the Argene AA identified more positives than the Biotest AA.

On Saturday, July 3, 2021, the Sonoma County Health Department was alerted to three cases of COVID-19 among residents of a homeless shelter in Santa Rosa, California. Among 153 shelter residents, 83 (54%) were fully vaccinated; 71 (86%) vaccinated residents had received the Janssen COVID-19 vaccine and 12 (14%) received an mRNA (Pfizer BioNTech or Moderna) COVID-19 vaccine. Within 1 month, 116 shelter residents (76%) received positive SARS-CoV-2 test results, including 66 (80%) of 83 fully vaccinated residents and 50 (71%) of 70 residents who were not fully vaccinated. Nine (14%) of 66 fully vaccinated cases, compared with 1 of 50 (2%) of unvaccinated cases, were hospitalized with COVID-19. All hospitalized cases had at least one underlying medical condition. Two deaths occurred, one in a vaccinated resident and one in a resident who was not fully vaccinated. Specimens from 52 residents underwent whole genome sequencing; all were identified as SARS-CoV-2 (the virus that causes COVID-19) AY.13, a sublineage of the B.1.617.2 (Delta) variant. These findings suggest that comprehensive measures including routine testing, individual quarantine, mask wearing, and physical distancing are needed in addition to vaccination in homeless shelters and other similar congregate settings, particularly those with residents who are at high risk for severe COVID-19.