High Post-infection Protection after COVID-19 Among Healthcare Workers: A Population-Level Observational Study Regarding SARS-CoV-2 Reinfection, Reactivation, and Re-positivity and its Severity

Introduction: Even though over a year has passed since the coronavirus 2019 (COVID-19) outbreak, our information regarding certain aspects of the disease, such as post-infection immunity is still very limited. This study aimed to evaluate post-infection protection and COVID-19 features among healthcare workers (HCWs), during three subsequent surges.Method: The study population consisted of all HCWs in either public or private hospitals in Fars province, Southern Iran from 20 April 2020 up to 20th February 2021. We calculated the rate of infection as the number of individuals with positive PCR tests divided by the cumulative number of person-days at risk. Poisson regression was utilized to calculate the adjusted rate ratio and estimated protection. Results: During the study period, a total of 30,546 PCR tests were performed among HCWs, of which 13,749 HCWs were positive. Among a total of 141 diagnosed cases who experienced a second episode of COVID-19, 44 (31.2%) cases of reactivation and relapse, and 97 (68.8% of infected and 1.81% of total HCWs) cases of reinfection was observed. The daily rate of infection was 4.72 for previously infected HCWs, while 2.20 for HCWs without previous infection. The estimated protection against repeat infection after a previous SARS-CoV-2 infection was 94.8% (95% CI: 93.6-95.7).Conclusion: Re-positivity, relapse, and reinfection of SARS-CoV-2 are quite rare in the population of HCWs. Also, after a first episode of infection, estimated protection of 94.8% was achieved against repeat infections.

ROLE OF REPEAT INFECTION IN THE DYNAMICS OF A SIMPLE MODEL OF WANING AND BOOSTING IMMUNITY

Some infectious diseases produce lifelong immunity while others only produce temporary immunity. In the case of short-lived immunity, the level of protection wanes over time and may be boosted upon re-exposure, via infection or vaccination. Previous work developed a simple model capturing waning and boosting immunity, known as the Susceptible-Infectious-Recovered-Waned-Susceptible (SIRWS) model, which exhibits rich dynamical behavior including supercritical and subcritical Hopf bifurcations among other structures. Here, we extend the bifurcation analyses of the SIRWS model to examine the influence of all parameters on these bifurcation structures. We show that the bistable region, involving both a stable fixed point and a stable limit cycle, exists only for a small region of biologically realistic parameter space. Furthermore, we contrast the SIRWS model with a modified version, where immune boosting may involve the occurrence of a secondary infection. Analysis of this extended model shows that oscillations and bistability, as found in the SIRWS model, depend on strong assumptions about infectivity and recovery rate from secondary infection. Understanding the dynamics of models of waning and boosting immunity is important for accurately assessing epidemiological data.

Dynamics of neutralizing antibody responses to SARS-CoV-2 in patients with COVID-19: an observational study

Our understanding of the protective immunity, particularly the long-term dynamics of neutralizing antibody (NAbs) response to SARS-CoV-2, is currently limited. We enrolled a cohort of 545 COVID-19 patients from Hubei, China, who were followed up up to 7 months, and determined the dynamics of NAbs to SARS-CoV-2 by using a surrogate virus neutralization test (sVNT). In our validation study, sVNT IC50 titers and the neutralization rate measured at a single dilution (1:20) were well correlated with FRNT titers (r = 0.85 and 0.84, respectively). The median time to seroconversion of NAbs was 5.5 days post onset of symptoms. The rate of positive sVNT was 52% in the first week, reached 100% in the third week, and remained above 97% till 6 months post onset. Quantitatively, NAbs peaked in the fourth week and only a quarter of patients had an estimated peak titer of >1000. NAbs declined with a half-time of 61 days (95% CI: 49–80 days) within the first two months, and the decay deaccelerated to a half-time of 104 days (95% CI: 86–130 days) afterward. The peak levels of NAbs were positively associated with severity of COVID-19 and age, while negatively associated with serum albumin levels. The observation that the low-moderate peak neutralizing activity and fast decay of NAbs in most naturally infected individuals called for caution in evaluating the feasibility of antibody-based therapy and vaccine durability. NAbs response positively correlated with disease severity, warning for the possibility of repeat infection in patients with mild COVID-19.

Will there be a third COVID-19 wave? A SVEIRD model based study of Indian situation.

Since first patient detected in India in late February, 2020, SARS-CoV-II virus is playing havoc on India. After the first wave, India is now riding the 2nd wave. As was in the case of European countries like Italy and UK, the 2nd wave is more contagious and at the time of writing this paper, the per day infection is as high as 400,000. The alarming thing is it is not uncommon that people is getting infected multiple time. On the other hand, mass vaccination has started step by step. There is also growing danger of potential 3rd wave is unavoidable, which can even infect kids and minors. In this situation, an estimation of the dynamics of SARS-CoV-2 is absolutely necessary to combat the pandemic. We have used a modified SEIRD model, that includes vaccination and repeat infection as well. We have studied India and 8 Indian states with varying SARS-CoV-2 infection. We have shown that, Covid-19 wave will be repeated time to time, but the intensity will slow down with time. In most possible situation, our calculation shows COVID-19 will remain as endemic for foreseeable future, unless we are able to increase our vaccination rate manifold.

MO976GENDER AND AGE DISPARITY IN INFECTIOUS COMPLICATIONS AFTER KIDNEY TRANSPLANTATION

Background and Aims Number of older patients with end stage kidney disease has been increasing, therefore there are increased number of older kidney transplant recipients. Potent immunosuppression (IS) used in patients after kidney transplantation (KTx) lowered the incidence of acute kidney rejection but increased the risk of post-transplant infection and sepsis as the most common non-cardiac cause of death. Older adults are at high risk of infections due to functional impairment and multiple comorbidities leading to poor outcome after KTx. Nowadays, no change in IS or prophylactic therapy is recommended based on the age of an adult KTx recipient. Female gender may be risk factor for infection after KTx due immunomodulatory effect of sex hormones such as estradiol. Methods The aim of our analysis was to find whether there are sex differences in the incidence of single and repeat infection and whether there is increased incidence of single and recurrent infectious complications in older kidney transplant recipients. Results Our analysis consisted of 100 patients after KTx (66 males, 34 females), average age 47,5 ± 12,6 years, treated with anti-thymocyte globulin as an induction IS. Male gender was a protective factor for the incidence of following infections in the 1st month after KTx: infection in general (P = 0.0054), recurrent infection (P = 0.0239), bacterial (P = 0.0125) and mycotic infection (P = 0.0103), recurrent bacterial infection (P = 0.0258). From the 1st to 6th month after KTx, female gender was identified as a risk factor for the incidence of infection in general (P = 0.0218), bacterial (P = 0.0186) and mycotic infection (P = 0.0318), repeat infection (P = 0.0216), recurrent bacterial infection (P = 0.0368). From 6th to 12th month after KTx, female gender was found as a risk factor for the incidence of bacterial infection (P = 0.0144), single infection (P = 0.0355), recurrent infection (P = 0.0007), single bacterial infection (P = 0.0309). Age > 60 years was not found as a risk factor for the incidence of single, repeat infection regarding its etiology. In our analysis we did not found correlation between gender and the incidence of single or recurrent infection of any etiology, we did not find significant differences in the severity of infections reflected by need for hospitalization, intensive care unit or use of vasopressors neither in gender, nor in older patients. In our study we did not confirm gender or age as a risk factor for the acute kidney rejection. Conclusion In our analysis, we found significant sex differences in the incidence of bacterial, viral, mycotic, single and repeat infection in different time intervals after kidney transplantation, while we did not confirmed age > 60 years is a risk factor for the infectious complications after KTx.

Repeat infection with SARS COV-2, a worrisome situation: report of two cases from India

Number of COVID cases and mortalities are still growing globally. There is no single treatment method found effective in reducing the disease severity. Several vaccines have been developed recently and most of them are under clinical trial only. Availability of an effective vaccine and its use at the community level is the only hope left with us. However, the emergence of re-infective cases from various part of the world has put a big question on the ongoing vaccination research and its use. Most of these re-infection cases reported were not studied for viral genome, different mutated virus causing repeat infection have been isolated in few reports only. In these situations, either a newer vaccine has to be developed every time for a new mutated virus or the multiple doses of the vaccine have to be administered if same strain of the virus is causing the re-infection. We report two cases from India who acquired repeat SARS COV 2 infection, adding up the much-required information in the current scenario.

COVID-19 Reinfection: A Case Series

Coronovirus Disease 2019 (COVID-19) manifests with a varied spectrum of symptoms ranging from asymptomatic disease to Acute Respiratory Distress Syndrome (ARDS) and death. Contrary to the expectation of the herd immunity in controlling the pandemic, reinfection with COVID-19 poses a new threat in the control of the pandemic. Authors hereby have described three cases who developed COVID-19 infection for the second time after complete recovery from the first infection. All three patients were less than 50 years of age with no co-morbidities. First case developed the second infection three weeks after having recovered from the first infection whereas second and third case developed repeat infection after two and four months of recovery respectively. The severity of the repeat infection along with the duration between the two infections has been discussed in this article.

Pathogens Associated With Repeat Versus Single Central-Line–Associated Bloodstream Infections, Acute-Care Hospitals, NHSN

Background: The NHSN is the nation’s largest surveillance system for healthcare-associated infections. Since 2011, acute-care hospitals (ACHs) have been required to report intensive care unit (ICU) central-line–associated bloodstream infections (CLABSIs) to the NHSN pursuant to CMS requirements. In 2015, this requirement included general medical, surgical, and medical-surgical wards. Also in 2015, the NHSN implemented a repeat infection timeframe (RIT) that required repeat CLABSIs, in the same patient and admission, to be excluded if onset was within 14 days. This analysis is the first at the national level to describe repeat CLABSIs. Methods: Index CLABSIs reported in ACH ICUs and select wards during 2015–2108 were included, in addition to repeat CLABSIs occurring at any location during the same period. CLABSIs were stratified into 2 groups: single and repeat CLABSIs. The repeat CLABSI group included the index CLABSI and subsequent CLABSI(s) reported for the same patient. Up to 5 CLABSIs were included for a single patient. Pathogen analyses were limited to the first pathogen reported for each CLABSI, which is considered to be the most important cause of the event. Likelihood ratio χ2 tests were used to determine differences in proportions. Results: Of the 70,214 CLABSIs reported, 5,983 (8.5%) were repeat CLABSIs. Of 3,264 nonindex CLABSIs, 425 (13%) were identified in non-ICU or non-select ward locations. Staphylococcus aureus was the most common pathogen in both the single and repeat CLABSI groups (14.2% and 12%, respectively) (Fig. 1). Compared to all other pathogens, CLABSIs reported with Candida spp were less likely in a repeat CLABSI event than in a single CLABSI event (P < .0001). Insertion-related organisms were more likely to be associated with single CLABSIs than repeat CLABSIs (P < .0001) (Fig. 2). Alternatively, Enterococcus spp or Klebsiella pneumoniae and K. oxytoca were more likely to be associated with repeat CLABSIs than single CLABSIs (P < .0001). Conclusions: This analysis highlights differences in the aggregate pathogen distributions comparing single versus repeat CLABSIs. Assessing the pathogens associated with repeat CLABSIs may offer another way to assess the success of CLABSI prevention efforts (eg, clean insertion practices). Pathogens such as Enterococcus spp and Klebsiella spp demonstrate a greater association with repeat CLABSIs. Thus, instituting prevention efforts focused on these organisms may warrant greater attention and could impact the likelihood of repeat CLABSIs. Additional analysis of patient-specific pathogens identified in the repeat CLABSI group may yield further clarification.Funding: NoneDisclosures: None