RESUMO
Memory B cells (MBCs) represent a second layer of immune protection against SARS-CoV-2. Whether MBCs elicited by mRNA vaccines can recognize the Omicron variant is of major concern. We used bio-layer interferometry to assess the affinity against the receptor-binding-domain (RBD) of Omicron spike of 313 naturally expressed monoclonal IgG that were previously tested for affinity and neutralization against VOC prior to Omicron. We report here that Omicron evades recognition from a larger fraction of these antibodies than any of the previous VOCs. Additionally, whereas 30% of these antibodies retained high affinity against Omicron-RBD, our analysis suggest that Omicron specifically evades antibodies displaying potent neutralizing activity against the D614G and Beta variant viruses. Further studies are warranted to understand the consequences of a lower memory B cell potency on the overall protection associated with current vaccines.
RESUMO
How a previous SARS-CoV-2 infection may amplify and model the memory B cell (MBC) response elicited by mRNA vaccines was addressed by a comparative longitudinal study of two cohorts, naive individuals and disease-recovered patients, up to 2 months after vaccination. The quality of the memory response was assessed by analysis of the VDJ repertoire, affinity and neutralization against variants of concerns (VOC), using unbiased cultures of 2452 MBCs. Upon boost, the MBC pool of recovered patients selectively expanded, further matured and harbored potent neutralizers against VOC. Maturation of the MBC response in naive individuals was much less pronounced. Nevertheless, and as opposed to their weaker neutralizing serum response, half of their RBD-specific MBCs displayed high affinity towards multiple VOC and one-third retained neutralizing potency against B.1.351. Thus, repeated vaccine challenges could reduce these differences by recall of affinity-matured MBCs and allow naive vaccinees to cope efficiently with VOC.
RESUMO
ImportanceNursing home (NH) residents are particularly vulnerable to SARS-CoV-2 infections and coronavirus disease 2019 (COVID-19) lethality. However, excess deaths in this population have rarely been documented. ObjectivesThe primary objective was to assess the number of excess deaths among NH residents during the first wave of the COVID-19 pandemic in France. The secondary objectives were to determine the number of excess deaths as a proportion of the total excess deaths in the general population and determine whether a harvesting effect was present. DesignWe studied a cohort of 494,753 adults (as of March 1st, 2020) aged 60 and over in 6,515 NHs in mainland France. This cohort was exposed to the first wave of the COVID-19 pandemic (from March 1st to May 31st, 2020) and was compared with the corresponding, reference cohorts from 2014 to 2019 (using data from the French National Health Data System). Main outcome and measuresThe main outcome was all-cause death. Weekly excess deaths and standardized mortality ratios (SMRs) were estimated. ResultThere were 13,505 excess deaths among NH residents. Mortality increased by 43% (SMR: 1.43). The mortality excess was higher among males than among females (SMR: 1.51 and 1.38, respectively) and decreased with age (SMRs in females: 1.61 in the 60-74 age group, 1.58 for 75-84, 1.41 for 85-94, and 1.31 for 95 or over; Males: SMRs: 1.59 for 60-74, 1.69 for 75-84, 1.47 for 85-94, and 1.41 for 95 or over). We did not observe a harvesting effect (up until August 30th, 2020). By extrapolating to all NH residents nationally (N=570,003), the latter accounted for 51% of the total excess deaths in the general population (N=15,114 out of 29,563). ConclusionNH residents accounted for about half of the total excess deaths in France during the first wave of the COVID-19 pandemic. The excess death rate was higher among males than females and among younger residents than among older residents. We did not observe a harvesting effect. A real-time mortality surveillance system and the identification of individual and environmental risk factors might help to design the future model of care for older dependent adults. Key pointsO_LIDuring the first wave of the COVID-19 pandemic in France, the mortality among nursing home residents increased by 43%. C_LIO_LINursing home residents accounted for 51% of the total excess deaths in France. C_LIO_LIThe excess mortality was higher among younger residents than among older residents. C_LIO_LIThe excess mortality was higher among males than among females. C_LIO_LIWe did not observe a harvesting effect during the study period (ending on August 30th, 2020, i.e., three months after the end of the first wave). C_LI
