Relative COVID-19 viral persistence and antibody kinetics

ImportanceThe COVID-19 antibody response is a critical indicator for evaluating immunity and also serves as the knowledge base for vaccine development. The picture is still not clear because of many limitations including testing tools, time of sampling, and the unclear impact of varying clinical status. In addition to these problems, antibody levels may not be equivalent to protective capacity.ObjectiveTo define the key factor for the different patterns of COVID-19 antibody response.DesignWe elucidated the antibody response with time-series throat and serum samples for viral loads and antibody levels, then used a neutralization test to evaluate protectiveness.SettingA medical center that typically cares for patients with moderate to severe diseases. Because of the low prevalence of COVID-19 in Taiwan and local government policy, however, we also admit COVID-19 patients with mild disease or even those without symptoms for inpatient care.ParticipantsRT-PCR-confirmed COVID-19 patients.ResultsWe found that only patients with relative persistence of virus at pharynx displayed strong antibody responses that were proportional to the pharyngeal viral load. They also had proportional neutralization titers per unit of serum. Although antibody levels decreased around 2 weeks after symptom onset, the neutralization efficacy per unit antibody remained steady and even continued to increase over time. The antibody response in patients with rapid virus clearance was weak, but the neutralization efficacy per unit antibody in these patients was comparable to those with persistent presence of virus. The deceased were with higher viral load, higher level of antibody, and higher neutralization titers in the serum, but the neutralization capacity per unit antibody is relatively low.Conclusions and RelevanceStrong antibody response depends on the relative persistence of the virus, instead of the absolute virus amount. The antibody response is still weak if large amount of virus is cleared quickly. The neutralization efficacy per unit antibody is comparable between high and low antibody patterns. Strong antibody response contains more inefficient and maybe even harmful antibodies. Low antibody response is also equipped with a capable B cell pool of efficient antibodies, which may expand with next virus encounter and confer protection.Key pointsQuestionThe key factor for the different “patterns” of COVID-19 antibody response.FindingsStrong antibody response depends on the relative persistence of the virus, instead of the absolute virus amount. The antibody response is still weak if large amount of virus is cleared quickly. The neutralization efficacy per unit antibody is comparable between high and low antibody patterns. High antibody level contains more inefficient antibodies.MeaningStrong response contains inefficient and maybe harmful antibodies. Low antibody response is also equipped with a capable B cell pool of efficient antibodies, which may expand with next virus encounter and confer protection.

Community Attraction and Avoidance in Chicago

We argue that the relative persistence of racial segregation is due, at least in part, to the process of residential search and the perceptions upon which those searches are based—a critical but often-ignored component of the residential sorting process. We examine where Chicago-area residents would “seriously consider” and “never consider” living, finding that community attraction and avoidance are highly racialized. Race most clearly shapes the residential perceptions and preferences of whites, and matters the least to blacks. Latinos would seriously consider moving to numerous neighborhoods, but controls for demographics and distance from the respondents’ home make Latino preferences much like those of whites. Critically, the geography of existing segregation begets further segregation: distance from current community significantly affects perceptions of the communities into which respondents might move. While neighborhood perception may cause persistent segregation, it may also offer hope for integration with appropriate policy interventions.

An Empirical Investigation of the Relationship between Profitability Persistence and Firms' Choice of Business Model: Evidence from the U.S. Airline Industry

ABSTRACT This paper examines the influence of a firm's business model on the relative persistence of profitability in the U.S. airline industry. The strategic management literature describes a firm's business model as reflecting how that firm chooses to compete in the marketplace. Given this linkage between business model, competition, and the marketplace, we conjecture that the persistence of profit margin and asset turnover ratios will be influenced by firms' choices of business model. Further, we hypothesize that this choice of business model influences the relative persistence of the individual revenue and expense components of current profit margin and asset turnover ratios for future profitability ratios. We test these conjectures by (1) partitioning our sample firms according to business model (network carriers versus low-cost carriers), and (2) decomposing sample firms' profit margin and asset turnover ratios into components relating to pricing policy, input cost control, and productivity. We find that the profit margin and asset turnover ratios of network carriers tend to be more persistent than those of low-cost carriers, and that this differential persistence is reflected in the associations between current revenue and expense components, and future profit margin and asset turnover ratios.