Neutralizing Antibody Responses Among Residents and Staff of Long-Term Care Facilities in the State of New Jersey During the First Wave of the COVID-19 Pandemic.

Expanding a previous study of the immune response to SARS-CoV-2 in 10 New Jersey long-term care facilities (LTCFs) during the first wave of the pandemic, this study characterized the neutralizing antibody (NAb) response to infection and vaccination among residents and staff. Sera from the original study were tested using the semi-quantitative enzyme-linked immunosorbent cPass neutralization-antibody detection assay. Almost all residents (97.8%) and staff (98.1%) who were positive for IgG S antibody to the spike protein were positive for NAb. In non-vaccinated subjects with a history of infection (positive polymerase chain reaction (PCR) or antigen test), the distribution of mean intervals from infection to serology date was not significantly different for S antibody positives versus negatives. More than 80% of both were positive at 10 months. Similarly, the mean NAb titer for residents and staff was not associated with interval from PCR/antigen positive to serology date, F = 0.1.01, Pr > F = 0.4269 and F = 0.77, Pr > F = 0.6548 respectively. Titers remained high as the interval reached 10 months. In vaccinees who had no history of infection, the NAb titer was near the test maximum when the serum was drawn seven or more days after the second vaccine dose. In staff the mean NAb titer increased significantly as the vaccine number increased from one to two doses, F = 11.69, Pr > F < 0.0001. NAb titers to SARS-CoV-2 in residents and staff of LTCFs were consistently high 10 months after infection and after two doses of vaccine. Ongoing study is needed to determine whether this antibody provides protection as the virus continues to mutate.

Antibody duration after infection from SARS-CoV-2 in the Texas Coronavirus Antibody Response Survey.

Understanding the duration of antibodies to the SARS-CoV-2 virus that causes COVID-19 is important to controlling the current pandemic. Participants from the Texas Coronavirus Antibody REsponse Survey (Texas CARES) with at least one nucleocapsid protein antibody test were selected for a longitudinal analysis of antibody duration. A linear mixed model was fit to data from participants (n= 4,553) with one to three antibody tests over 11 months (10/1/2020-9/16/2021), and models fit showed that expected antibody response after COVID-19 infection robustly increases for 100 days post-infection, and predicts individuals may remain antibody positive from natural infection beyond 500 days, depending on age, body mass index, smoking or vaping use, and disease severity (hospitalized or not; symptomatic or not).

The duration and breadth of antibody responses to 3-dose of inactivated COVID-19 vaccinations in healthy blood donors: An observational study.

Objectives: We aimed to evaluate the duration and breadth of antibodies elicited by inactivated COVID-19 vaccinations in healthy blood donors. Methods: We performed serological tests on 1,417 samples from 658 blood donors who received two (n=357), or three (n=301) doses of COVID-19 inactivated vaccine. We also accessed the change in antibody response before and after booster vaccination in 94 participants and their neutralization breadth to the current variants after the booster. Results: Following vaccination, for either the 2- or 3-dose, the neutralizing antibodies (nAbs) peaked with about 97% seropositivity approximately within one month but subsequently decreased over time. Of plasmas collected 6-8 months after the last immunization, the nAb seropositivities were 37% and 85% in populations with 2-dose and 3-dose vaccinations, respectively. The nAbs of plasma samples (collected between 2-6 weeks after the 3rd dose) from triple-vaccinated donors (n=94) showed a geometric mean titer of 145.3 (95% CI: 117.2 to 180.1) against the ancestral B.1, slightly reduced by 1.7-fold against Delta variant, but markedly decreased by 4-6 fold in neutralizing Omicron variants, including the sub-lineages of BA.1 (5.6-fold), BA.1.1 (6.0-fold), BA.2 (4.2-fold), B.2.12.1 (6.2-fold) and BA.4/5 (6.5-fold). Conclusion: These findings suggested that the 3rd dose of inactivated COVID-19 vaccine prolongs the antibody duration in healthy populations, but the elicited-nAbs are less efficient in neutralizing circulating Omicron variants.

Over 1-year duration and age difference of SARS-CoV-2 antibodies in convalescent COVID-19 patients.

Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglouilin G (IgG) and immunoglouilin M (IgM) antibodies have been widely used to assist clinical diagnosis. Our previous study reported a discrepancy in SARS-CoV-2 antibody response between male and female coronavirus disease 2019 (COVID-19) patients. However, the duration and discrepancy between ages as well as sexes of SARS-CoV-2 antibody in convalescent COVID-19 patients have not been clarified. In this study, a total of 538 health-examination individuals who were confirmed with SARS-CoV-2 infection a year ago were enrolled. Blood samples were collected and detected for IgM and IgG antibodies. Among these convalescent patients, 12.80% were detected positive for IgM antibodies. The positive rates for IgM antibody were close between sexes: for males, this is 9.17% and for females 13.75%. However, the IgG antibody was detected positive in as much as 82.90% convalescent patients and the positive rates were nearly the same between males (82.57%) and females (82.98%). Besides this, the level of IgM and IgG antibodies showed no difference between male and female convalescent patients. The level of IgG antibodies showed a significant difference between ages. The elder patients (over 35 years old) maintained a higher level of IgG antibody than the younger patients (under or equal 35 years old) after recovering for 1 year. In addition, IgG antibody was more vulnerable to disappear in younger patients than in elder patients. Overall, our study identified over 1-year duration of SARS-CoV-2 antibody and age difference of IgG antibody response in convalescent COVID-19 patients. These findings may provide new insights into long-term humoral immune response, vaccines efficacy and age-based personalized vaccination strategies.

Evaluation of a SARS-CoV-2 Capture IgM Antibody Assay in Convalescent Sera.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for a global pandemic with over 152 million cases and 3.19 million deaths reported by early May 2021. Understanding the serological response to SARS-CoV-2 is critical to determining the burden of infection and disease (coronavirus disease 2019 [COVID-19]) and transmission dynamics. We developed a capture IgM assay because it should have better sensitivity and specificity than the commonly used indirect assay. Here, we report the development and performance of a capture IgM enzyme-linked immunosorbent assay (ELISA) and a companion indirect IgG ELISA for the spike (S) and nucleocapsid (N) proteins and the receptor-binding domain (RBD) of S. We found that among the IgM ELISAs, the S ELISA was positive in 76% of 55 serum samples from SARS-CoV-2 PCR-positive patients, the RBD ELISA was positive in 55% of samples, and the N ELISA was positive in 15% of samples. The companion indirect IgG ELISAs were positive for S in 89% of the 55 serum samples, RBD in 78%, and N in 85%. While the specificities for IgM RBD, S, and N ELISAs and IgG S and RBD ELISAs were 97% to 100%, the specificity of the N IgG ELISA was lower (89%). RBD-specific IgM antibodies became undetectable by 3 to 6 months, and S IgM reached low levels at 6 months. The corresponding IgG S, RBD, and N antibodies persisted with some decreases in levels over this time period. These capture IgM ELISAs and the companion indirect IgG ELISAs should enhance serologic studies of SARS-CoV-2 infections. IMPORTANCE Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has inflicted tremendous loss of lives, overwhelmed health care systems, and disrupted all aspects of life worldwide since its emergence in Wuhan, China, in December 2019. Detecting current and past infection by PCR or serology is important to understanding and controlling SARS-CoV-2. With increasing prevalence of past infection or vaccination, IgG antibodies are less helpful in diagnosing a current infection. IgM antibodies indicate a more recent infection and can supplement PCR diagnosis. We report an alternative method, capture IgM, to detect serum IgM antibodies, which should be more sensitive and specific than most currently used methods. We describe this capture IgM assay and a companion indirect IgG assay for the SARS-CoV-2 spike (S), nucleocapsid (N), and receptor-binding domain (RBD) proteins. These assays can add value to diagnostic and serologic studies of coronavirus disease 2019 (COVID-19).

A mathematical model for COVID-19 pandemic-SIIR model: Effects of asymptomatic individuals.

A new mathematical model called SIIR model is constructed to describe the spread of infection by taking account of the characteristics of COVID-19 and is verified by the data from Japan. The following features of COVID-19: (a) there exist presymptomatic individuals who have infectivity even during the incubation period, (b) there exist asymptomatic individuals who can freely move around and play crucial roles in the spread of infection, and (c) the duration of immunity may be finite, are incorporated into the SIIR model. The SIIR model has the advantage of being able to explicitly handle asymptomatic individuals who are delayed in discovery or are extremely difficult to be discovered in the real world. It is shown that the conditions for herd immunity in the SIIR model become more severe than those in the SIR model; that is, the presence of asymptomatic individuals increases herd immunity threshold (HIT).