Pregnancy outcomes in women with severe acute respiratory syndrome coronavirus 2 reinfections compared to those with a single infection: a retrospective cohort study.

BACKGROUND: To assess pregnancy outcomes in women with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection. METHODS: This was a retrospective cohort study that included pregnant women who contracted coronavirus disease 2019 (COVID-19) once or twice during pregnancy and who gave birth between 1 October 2022 and 15 August 2023 in Shanghai First Maternity and Infant Hospital (Shanghai, China). We collected their clinical data and compared the frequency of adverse pregnancy outcomes between the reinfection group and the primary infection group, such as preterm birth, fetal growth restriction (FGR), hypertensive disorders of pregnancy (HDP), common pregnancy-related conditions, birth weight, and neonatal unit admission. RESULTS: We observed a 7.7% reinfection rate among the 1,405 women who contracted COVID-19 during pregnancy. There were no significant differences in the frequency of preterm birth, FGR, HDP, other common pregnancy-related conditions, birth weight, or rate of neonatal unit admission between the reinfection and single infection groups. All our participants were unvaccinated, and all had mild symptoms. CONCLUSION: Our study showed no significant association between SARS-CoV-2 reinfection and adverse pregnancy outcomes.

Hepatitis C (HCV) Reinfection and Risk Factors among Clients of a Low-Threshold Primary Healthcare Service for People Who Inject Drugs in Sydney, Australia.

Hepatitis C (HCV) reinfection studies have not focused on primary healthcare services in Australia, where priority populations including people who inject drugs (PWID) typically engage in healthcare. We aimed to describe the incidence of HCV reinfection and associated risk factors in a cohort of people most at risk of reinfection in a real-world community setting. We conducted a secondary analysis of routinely collected HCV testing and treatment data from treatment episodes initiated with direct-acting antiviral (DAA) therapy between October 2015 and June 2021. The overall proportion of clients (N = 413) reinfected was 9% (N = 37), and the overall incidence rate of HCV reinfection was 9.5/100PY (95% CI: 6.3-14.3). Reinfection incidence rates varied by sub-group and were highest for Aboriginal and/or Torres Strait Islander people (20.4/100PY; 95% CI: 12.1-34.4). Among PWID (N= 321), only Aboriginality was significantly associated with reinfection (AOR: 2.73, 95% CI: 1.33-5.60, p = 0.006). High rates of HCV reinfection in populations with multiple vulnerabilities and continued drug use, especially among Aboriginal and Torres Strait Islander people, highlight the need for ongoing regular HCV testing and retreatment in order to achieve HCV elimination. A priority is resourcing testing and treatment for Aboriginal and/or Torres Strait Islander people. Our findings support the need for novel and holistic healthcare strategies for PWID and the upscaling of Indigenous cultural approaches and interventions.

Epidemiological characteristics and antibody kinetics of elderly population with booster vaccination following both Omicron BA.5 and XBB waves in China.

After the termination of zero-COVID-19 policy, the populace in China has experienced both Omicron BA.5 and XBB waves. Considering the poor antibody responses and severe outcomes observed among the elderly following infection, we conducted a longitudinal investigation to examine the epidemiological characteristics and antibody kinetics among 107 boosted elderly participants following the Omicron BA.5 and XBB waves. We observed that 96 participants (89.7%) were infected with Omicron BA.5, while 59 (55.1%) participants were infected with Omicron XBB. Notably, 52 participants (48.6%) experienced dual infections of both Omicron BA.5 and XBB. The proportion of symptomatic cases appeared to decrease following the XBB wave (18.6%) compared to that after the BA.5 wave (59.3%). Omicron BA.5 breakthrough infection induced lower neutralizing antibody titers against XBB.1.5, BA.2.86, and JN.1, while reinfection with Omicron XBB broadened the antibody responses against all measured Omicron subvariants and may alleviate the wild type-vaccination induced immune imprinting. Boosted vaccination type and comorbidities were the significant factors associated with antibody responses. Updated vaccines based on emerging severe acute respiratory syndrome coronavirus 2 variants are needed to control the Coronavirus Disease 2019 pandemic in the elderly.

Investigation of epidemiological and clinical characteristics of people infected with SARS-CoV-2 during the second pandemic of COVID-19 in Chengdu, China.

Objective: This study investigated the epidemiological and clinical characteristics of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infected patients during the second pandemic of COVID-19 (coronavirus disease of 2019) in Chengdu, China. Furthermore, the differences between first infection and re-infection cases were also compared and analyzed to provide evidence for better prevention and control of SARS-CoV-2 re-infection. Methods: An anonymous questionnaire survey was conducted using an online platform (wjx.cn) between May 20, 2023 to September 12, 2023. Results: This investigation included 62.94% females and 32.97% of them were 18-30 years old. Furthermore, 7.19-17.18% of the participants either did not receive vaccination at all or only received full vaccination, respectively. Moreover, 577 (57.64%) participants were exposed to cluster infection. The clinical manifestations of these patients were mainly mild to moderate; 78.18% of participants had a fever for 1-3 days, while 37.84% indicated a full course of disease for 4-6 days. In addition, 40.66% of the participants had re-infection and 72.97% indicated their first infection approximately five months before. The clinical symptoms of the first SARS-CoV-2 infection were moderate to severe, while re-infection indicated mild to moderate symptoms (the severity of symptoms other than diarrhea and conjunctival congestion had statistically significant differences) (p < 0.05). Moreover, 70.53 and 59.21% of first and re-infection cases had fever durations of 3-5 and 0-2 days, respectively. Whereas 47.91 and 46.40% of first and re-infection cases had a disease course of 7-9 and 4-6 days. Conclusion: The SARS-CoV-2 infected individuals in Chengdu, China, during the second pandemic of COVID-19 had mild clinical symptoms and a short course of disease. Furthermore, compared with the first infection, re-infection cases had mild symptoms, low incidences of complications, short fever duration, and course of disease.

Pattern and predictor of hookworm re-infection among schoolchildren in three districts of Amhara Region, northwest Ethiopia.

BACKGROUND: Despite integrated prevention and control measures, the prevalence of hookworm is still high in Ethiopia. The re-infection rates and predictors are poorly addressed. Therefore, this study aimed to determine the patterns of hookworm re-infection rates and predictors among schoolchildren in northwest Ethiopia. METHODS: A prospective follow-up study was conducted among 86 schoolchildren from May to December 2022. Data on predictors was collected using a questionnaire. Stool samples were collected and processed via Kato-Katz, McMaster, and spontaneous tube sedimentation techniques. All hookworm-infected children were treated with albendazole and followed for six months. The re-infection rates of hookworm were checked in the 4th and 6th months. Data was entered into Epi-data version 3.1 and analysed using SPSS version 25. Descriptive statistics were used to compute the re-infection rate. The associations of predictors with hookworm re-infection rates were calculated by logistic regression. Variables with a p-value < 0.05 were considered statistically significant. RESULTS: Of the 86, 81 schoolchildren completed the study. The prevalence of hookworm re-infection in the 4th and 6th months was 23.5% and 33.3%, respectively. Living with family members greater than five (p = .017), poor utilization of latrine (p = .008), infrequent shoe wear (p = .039), and participating in irrigation (p = .020) were the predictors significantly associated with hookworm re-infections. CONCLUSIONS: The re-infection rate was high during the fourth and sixth months. Participating in irrigation, infrequent shoe wear, and poor latrine utilization were predictors of hookworm re-infection. Therefore, mass drug administration, regular shoe wearing, and health education should be advocated.

Dynamics of SARS-CoV-2 antibodies after natural infection: insights from a study on Pasteur Institute of Tunis employees.

This study aimed to assess the kinetics of antibodies against the SARS-CoV-2, following natural infection in a cohort of employees of the Institut Pasteur de Tunis (IPT) and to assess the risk of reinfection over a 12-months follow-up period. A prospective study was conducted among an open cohort of IPT employees with confirmed SARS-CoV-2 infection that were recruited between September 2020 and March 2021. Sera samples were taken at 1, 3, 6, 9 and 12 months after confirmation of COVID-19 infection and tested for SARS-CoV-2-specific immunoglobulin G (IgG) antibodies to the spike (S-RBD) protein (IgG anti-S-RBD) and for neutralizing antibodies. Participants who had an initial decline of IgG anti-S-RBD and neutralizing antibodies followed by a subsequent rise in antibody titers as well as those who tested positive for SARS-CoV-2 by RT-PCR after at least 60 days of follow up were considered as reinfected. In total, 137 individuals were included with a mean age of 44.7 ± 12.3 years and a sex-ratio (Male/Female) of 0.33. Nearly all participants (92.7%) were symptomatic, and 2.2% required hospitalization. Among the 70 participants with three or more prospective blood samples, 32.8% were reinfected among whom 11 (47.8%) reported COVID-19 like symptoms. Up to 12 months of follow up, 100% and 42.9% of participants had detectable IgG anti-S-RBD and neutralizing antibodies, respectively. This study showed that humoral immune response following COVID-19 infection may persist up to 12 months after infection despite the potential risk for reinfection that is mainly explained by the emergence of new variants.

Long-term monitoring of SARS-CoV-2 seroprevalence and variants in Ethiopia provides prediction for immunity and cross-immunity.

Under-reporting of COVID-19 and the limited information about circulating SARS-CoV-2 variants remain major challenges for many African countries. We analyzed SARS-CoV-2 infection dynamics in Addis Ababa and Jimma, Ethiopia, focusing on reinfection, immunity, and vaccination effects. We conducted an antibody serology study spanning August 2020 to July 2022 with five rounds of data collection across a population of 4723, sequenced PCR-test positive samples, used available test positivity rates, and constructed two mathematical models integrating this data. A multivariant model explores variant dynamics identifying wildtype, alpha, delta, and omicron BA.4/5 as key variants in the study population, and cross-immunity between variants, revealing risk reductions between 24% and 69%. An antibody-level model predicts slow decay leading to sustained high antibody levels. Retrospectively, increased early vaccination might have substantially reduced infections during the delta and omicron waves in the considered group of individuals, though further vaccination now seems less impactful.

High Post-Infection Protection after COVID-19 among Healthcare Workers: A Population-Level Observational Study.

Background: Even though a few years have passed since the coronavirus disease 2019 (COVID-19) outbreak, information regarding certain aspects of the disease, such as post-infection immunity, is still quite limited. This study aimed to evaluate post-infection protection and COVID-19 features among healthcare workers (HCWs), during three successive surges, as well as the rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection, reactivation, re-positivity, and severity. Methods: This cross-sectional population-level observational study was conducted from 20 April 2020 to 18 February 2021. The study population included all HCWs in public or private hospitals in Fars Province, Southern Iran. The infection rate was computed as the number of individuals with positive polymerase chain reaction (PCR) tests divided by the total number of person-days at risk. The re-infection was evaluated after 90 days. Results: A total of 30,546 PCR tests were performed among HCWs, of which 13,749 (61.94% of total HCWs) were positive. Considering the applied 90-day threshold, there were 44 (31.2%) cases of reactivation and relapse, and 97 (68.8% of infected and 1.81% of total HCWs) cases of reinfection among 141 (2.64%) diagnosed cases who experienced a second episode of COVID-19. There was no significant difference in symptoms (P=0.65) or the necessity for ICU admission (P=0.25). The estimated protection against repeated infection after a previous SARS-CoV-2 infection was 94.8% (95% CI=93.6-95.7). Conclusion: SARS-CoV-2 re-positivity, relapse, and reinfection were rare in the HCW population. After the first episode of infection, an estimated 94.8% protection against recurring infections was achieved. A preprint version of this manuscript is available at DOI:10.21203/rs.3.rs-772662/v1 (https://www.researchsquare.com/article/rs-772662/v1).

The symptoms and interval of Omicron SARS-CoV-2 reinfection among healthcare workers in a hospital of Southern China: a cross-sectional study.

BACKGROUND: The prevalence and distinction between first Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and reinfection with the Omicron variant among healthcare workers (HCWs) remain unclear. METHODS: A cross-sectional study was conducted at a hospital in Southern China. The study included 262 HCWs who were infected with SARS-CoV-2 between April and June 2023, with 101 cases of first infection and 161 ones of reinfection. Student's t-test, Analysis of Variance (ANOVA), and Mann-Whitney U tests were used based on the distribution of quantitative variables. Pearson's chi-square and Fisher's exact tests were used based on the expected frequencies of categorical variables. RESULTS: The reinfection rate among HCWs was 11.5% (161/1406). The majority of the infected HCWs were female (212/262, 80.9%, first infection vs. reinfection: 76.2% vs. 83.9%). The nursing staff, had the highest percentage of SARS-CoV-2 infection (42.0%), especially of its reinfection (47.8%). Out of the 262 infected individuals, 257 had received SARS-CoV-2 vaccination, primarily inactivated vaccines (243/257, 91.1%). The first infection group, which received four doses (24, 23.8%), was significantly higher than that in the reinfection group (6, 3.7%) (P < 0.001). The proportion of asymptomatic infections among HCWs in the two groups was 1.0% and 1.2%. The main symptoms during the first infection and reinfection were fever (83.2% and 50.9%) and sore throat (78.2% and 77.0%). There were significant differences in the prevalence of fever (83.2% vs. 50.9%), rhinorrhea (45.5% vs. 60.9%) and myalgia (56.4% vs. 37.9%) between the first infection and reinfection (P < 0.05). The average interval for SARS-CoV-2 reinfection was 149.9 (range: 114-182, SD = 11.9) days. Notably, physicians had the shortest average interval of 142.8 (8.8) days, while management and administrative staff had the longest average interval of 153.8 (13.5) days. CONCLUSIONS: Although the symptoms of HCWs during reinfection with SARS-CoV-2 were milder, the high reinfection rate and short interval between infections indicate the need to enhance monitoring and protective measures for HCWs during the epidemic.

Stuck in pandemic uncertainty: a review of the persistent effects of COVID-19 infection in immune-deficient people.

BACKGROUND: People who are immune-deficient/disordered (IDP) are underrepresented in COVID-19 studies. Specifically, there is limited research on post-SARS-CoV-2 infection outcomes, including viral persistence and long-term sequelae in these populations. OBJECTIVES: This review aimed to examine the published literature on the occurrence of persistent SARS-CoV-2 positivity, relapse, reinfections, variant coinfection, and post-acute sequelae of COVID-19 in IDP. Although the available literature largely centred on those with secondary immunodeficiencies, studies on people with inborn errors of immunity are also included. SOURCES: PubMed was searched using medical subject headings terms to identify relevant articles from the last 4 years. Articles on primary and secondary immunodeficiencies were chosen, and a special emphasis was placed on including articles that studied people with inborn errors of immunity. The absence of extensive cohort studies including these individuals has limited most articles in this review to case reports, whereas the articles focusing on secondary immunodeficiencies include larger cohort, case-control, and cross-sectional studies. Articles focusing solely on HIV/AIDS were excluded. CONTENT: Scientific literature suggests that IDP of any age are more likely to experience persistent SARS-CoV-2 infections. Although adult IDP exhibits a higher rate of post-acute sequelae of COVID-19, milder COVID-19 infections in children may reduce their risk of experiencing post-acute sequelae of COVID-19. Reinfections and coinfections may occur at a slightly higher rate in IDP than in the general population. IMPLICATIONS: Although IDP experience increased viral persistence and inter-host evolution, it is unlikely that enough evidence can be generated at the population-level to support or refute the hypothesis that infections in IDP are significantly more likely to result in variants of concern than infections in the general population. Additional research on the relationship between viral persistence and the rate of long-term sequelae in IDP could inform the understanding of the immune response to SARS-CoV-2 in IDP and the general population.

Comparative outcomes of SARS-CoV-2 primary and reinfection in older adult patients.

Background: The outcomes of older adult people acquiring SARS-CoV-2 reinfection was unclear. This study aimed to compare the outcomes of older adult patients with COVID-19 reinfection and those with primary infection. Methods: This retrospective cohort study used electronic medical records from the TriNetX Research Network. Older adult patients (aged ≥65 years) with COVID-19 between January 1, 2022, and December 31, 2022, were included in the study. The patients were subsequently categorized into reinfection or primary infection groups, according to whether they manifested two distinct COVID-19 episodes with an intervening period of more than 90 days. Propensity score matching was performed for covariate adjustment between the reinfection and primary infection groups. The primary outcome was a composite outcome, including emergency department visits, hospitalization, intensive care unit admission, mechanical ventilation use, and mortality, following primary infection and reinfection. Results: After matching, 31,899 patients were identified in both the reinfection and primary infection groups. The risk of primary composite outcomes was 7.15% (n = 2,281) in the reinfection group and 7.53% (n = 2,403) in the primary infection group. No significant difference in the primary outcome was observed between groups (HR, 0.96; 95% CI, 0.91 to 1.02, p = 0.17). In addition, there was no significant differences between the reinfection and primary infection groups in terms of emergency department visit (HR, 1.03; 95% CI, 0.95 to 1.11, p = 0.49), all-cause hospitalization (HR, 0.94; 95% CI, 0.86 to 1.02, p = 0.14), intensive care unit admission (HR, 0.92; 95% CI, 0.67 to 1.28, p = 0.62), mechanical ventilation use (HR,1.35 95% CI, 0.69 to 2.64 p = 0.38), and all-cause mortality (HR, 0.94; 95% CI, 0.74 to 1.20, p = 0.62). Conclusion: There were no significant differences in clinical outcomes between older adult patients with COVID-19 reinfection and those with primary infection.

Risk of SARS-CoV-2 reinfection during multiple Omicron variant waves in the UK general population.

SARS-CoV-2 reinfections increased substantially after Omicron variants emerged. Large-scale community-based comparisons across multiple Omicron waves of reinfection characteristics, risk factors, and protection afforded by previous infection and vaccination, are limited. Here we studied ~45,000 reinfections from the UK's national COVID-19 Infection Survey and quantified the risk of reinfection in multiple waves, including those driven by BA.1, BA.2, BA.4/5, and BQ.1/CH.1.1/XBB.1.5 variants. Reinfections were associated with lower viral load and lower percentages of self-reporting symptoms compared with first infections. Across multiple Omicron waves, estimated protection against reinfection was significantly higher in those previously infected with more recent than earlier variants, even at the same time from previous infection. Estimated protection against Omicron reinfections decreased over time from the most recent infection if this was the previous or penultimate variant (generally within the preceding year). Those 14-180 days after receiving their most recent vaccination had a lower risk of reinfection than those >180 days from their most recent vaccination. Reinfection risk was independently higher in those aged 30-45 years, and with either low or high viral load in their most recent previous infection. Overall, the risk of Omicron reinfection is high, but with lower severity than first infections; both viral evolution and waning immunity are independently associated with reinfection.

SARS-CoV-2 reinfection with Omicron variant in Shaanxi Province, China: December 2022 to February 2023.

BACKGROUND: Prior to December 2022, there were no reports of reinfection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Shaanxi province, China. Since then, China has refined its strategy in response to coronaviruses. The purpose of this study was to determine the incidence of SARS-CoV-2 reinfections and its contributing factors, as well as to compare clinical characteristics between first and second episodes of infection in Shaanxi Province, China between December 2022 and February 2023. METHODS: We conducted a cross-sectional study using an epidemiological survey system and electronic questionnaires to investigate the incidence of SARS-CoV-2 reinfection among previously infected individuals during the epidemic wave owing to the Omicron variant that began in December 2022. A logistic regression model was used to determine those factors influencing SARS-CoV-2 reinfections. RESULTS: According to the virus variant that caused the first infection, the rate of reinfection for the Omicron variants was 1.28%, 1.96%, and 5.92% at 2-3 months, 4-5 months, and 7-9 months after the primary infection, respectively. The rate of reinfection for the Delta variants was 25.10% 11-12 months after the primary infection. Females, adults between 18 and 38 years and being a medical worker were associated with an increased risk of reinfection. Fever, cough, sore throat and fatigue were the four most common clinical symptoms during both first and second COVID-19 infections. CONCLUSIONS: In our study, the rate of SARS-CoV-2 reinfection increased over time during epidemic waves predominantly involving the Omicron variant in Shaanxi province, China. Large-scale infections are less likely in subsequent Omicron epidemic waves. Nevertheless, it is essential to continuously monitor cases of infection as well as continue surveillance for emerging SARS-CoV-2 variants.

Breakthrough infection and reinfection in patients with mpox.

Recently, patients with Mpox breakthrough infection or reinfection were constantly reported. However, the induction, risk factors, and important clinical symptoms of breakthrough infection and reinfection of Mpox virus (MPXV), as well as the factors affecting the effectiveness of Mpox vaccine are not characterized. Herein, a literature review was preformed to summarize the risk factors and important clinical symptoms of patients with Mpox breakthrough infection or reinfection, as well as the factors affecting the effectiveness of smallpox vaccine against Mpox. Results showed that MSM sexual behavior, condomless sexual behavior, multiple sexual partners, close contact, HIV infection, and the presence of comorbidity are important risk factors for Mpox breakthrough infection and reinfection. Genital ulcers, proctitis, and lymphadenopathy are the important clinical symptoms of Mpox breakthrough infection and reinfection. The effectiveness of emergent vaccination of smallpox vaccine for post-exposure of MPXV is associated with smallpox vaccination history, interval between exposure and vaccination, and history of HIV infection. This review provides a better understanding for the risk factors and important clinical symptoms of Mpox breakthrough infection and reinfection, as well as the formulation of Mpox vaccine vaccination strategies.

HIV Infection Modifies the Role of Prior Treponema pallidum Infection in the Clinical Presentation of Early Syphilis Among Adult Patients From Sexually Transmitted Infection Clinics in Peru.

BACKGROUND: We aimed to compare the clinical presentations (symptomatic vs. asymptomatic) with prior Treponema pallidum infection status (first infection vs. reinfection) among people with early syphilis. METHODS: We used data from PICASSO, a cohort study in Peru that enrolled people with active syphilis from May 2019 to August 2021. Study participants had early syphilis and a prior syphilis serological test result within the prior 12 months to determine prior T. pallidum infection status. We calculated prevalence ratios (PRs) of symptomatic clinical presentation (primary or secondary syphilis) by prior T. pallidum infection status, stratified by HIV infection status. In addition, we explored the association of prior T. pallidum infection status and lesion presentation, stratified by primary and secondary syphilis cases, using the Fisher exact test. RESULTS: We include 84 T. pallidum reinfection cases and 61 first infection cases. We found increased frequency of symptomatic clinical presentation among first-infection cases (39% vs. 20%; PR, 1.94; P = 0.014). This association was stronger among persons living without HIV infection (38% vs. 7%; adjusted PR, 6.63; P = 0.001) in comparison to those living with HIV infection (45% vs. 34%; adjusted PR, 1.38; P = 0.458). Among secondary syphilis cases, more participants from the reinfection group reported that their lesions improved 1 week after treatment (100% vs. 29%, P = 0.045) compared with those with a first infection. Among the primary syphilis cases, all participants reported that their lesions improved 1 week after treatment. CONCLUSIONS: Prior syphilis was associated with a decreased prevalence of symptomatic reinfection, especially among persons not living with HIV infection.

Frequency and risk of SARS-CoV-2 reinfections in Norway: a nation-wide study, February 2020 to January 2022.

BACKGROUND: SARS-CoV-2 reinfection rates have been shown to vary depending on the circulating variant, vaccination status and background immunity, as well as the time interval used to identify reinfections. This study describes the frequency of SARS-CoV-2 reinfections in Norway using different time intervals and assesses potential factors that could impact the risk of reinfections during the different variant waves. METHODS: We used linked individual-level data from national registries to conduct a retrospective cohort study including all cases with a positive test for SARS-CoV-2 from February 2020 to January 2022. Time intervals of 30, 60, 90 or 180 days between positive tests were used to define potential reinfections. A multivariable Cox regression model was used to assess the risk of reinfection in terms of variants adjusting for vaccination status, demographic factors, and underlying comorbidities. RESULTS: The reinfection rate varied between 0.2%, 0.6% and 5.9% during the Alpha, Delta and early Omicron waves, respectively. In the multivariable model, younger age groups were associated with a higher risk of reinfection compared to older age groups, whereas vaccination was associated with protection against reinfection. Moreover, the risk of reinfection followed a pattern similar to risk of first infection. Individuals infected early in the pandemic had higher risk of reinfection than individuals infected in more recent waves. CONCLUSIONS: Reinfections increased markedly during the Omicron wave. Younger individuals, and primary infections during earlier waves were associated with an increased reinfection risk compared to primary infections during more recent waves, whereas vaccination was a protective factor. Our results highlight the importance of age and post infection waning immunity and are relevant when evaluating vaccination polices.

Impact on the time elapsed since SARS-CoV-2 infection, vaccination history, and number of doses, on protection against reinfection.

SARS-CoV-2 reinfections have been frequent, even among those vaccinated. The aim of this study is to know if hybrid immunity (infection + vaccination) is affected by the moment of vaccination and number of doses received. We conducted a retrospective study in 746 patients with a history of COVID-19 reinfection and recovered the dates of infection and reinfection and vaccination status (date and number of doses). To assess differences in the time to reinfection(tRI) between unvaccinated, vaccinated before 6 months, and later; and comparing one, two or three doses (incomplete, complete and booster regime) we performed the log-rank test of the cumulative incidence calculated as 1 minus the Kaplan-Meier estimator. Also, an adjusted Cox-regression was performed to evaluate the risk of reinfection in all groups. The tRI was significantly higher in those vaccinated vs. non-vaccinated (p < 0.001). However, an early incomplete regime protects similar time than not receiving a vaccine. Vaccination before 6 months after infection showed a lower tRI compared to those vaccinated later with the same regime (adj-p < 0.001). Actually, early vaccination with complete and booster regimes provided lower length of protection compared to vaccinating later with incomplete and complete regime, respectively. Vaccination with complete and booster regimes significantly increases the tRI (adj-p < 0.001). Vaccination increases the time it takes for a person to become reinfected with SARS-CoV-2. Increasing the time from infection to vaccination increases the time in which a person could be reinfected and reduces the risk of reinfection, especially in complete and booster regimes. Those results emphasize the role of vaccines and boosters during the pandemic and can guide strategies on future vaccination policy.

Risk of SARS-CoV-2 Reinfection in Children Within the 12 Months Following Mild COVID-19: Insights From a Survey Study.

Understanding the correlation between immune response and protection from COVID-19 will play a pivotal role in predicting the effectiveness of vaccines in children. We studied SARS-CoV-2 reinfection risk in children 12 months post-mild COVID-19. Children under 5 years old exhibited lower reinfection risk than older infected or vaccinated siblings during 12 months postimmunization.

COVID-19 Reinfection Has Better Outcomes Than the First Infection in Solid Organ Transplant Recipients.

BACKGROUND: Solid organ transplant recipients face an increased risk of severe coronavirus disease 2019 (COVID-19) and are vulnerable to repeat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. In nonimmunocompromised individuals, SARS-CoV-2 reinfections are milder likely because of cross-protective immunity. We sought to determine whether SARS-CoV-2 reinfection exhibits milder manifestations than primary infection in transplant recipients. METHODS: Using a large, prospective cohort of adult transplant patients with COVID-19, we identified patients with SARS-CoV-2 reinfections. We performed a 1:1 nearest neighbor propensity score matching to control potential confounders, including the COVID-19 variant. We compared outcomes including oxygen requirement, hospitalization, and intensive care unit admission within 30 d after diagnosis between patients with reinfection and those with the first episode of COVID-19. RESULTS: Between 2020 and 2023, 103 reinfections were identified in a cohort of 1869 transplant recipients infected with SARS-CoV-2 (incidence of 2.7% per year). These included 50 kidney (48.5%), 27 lung (26.2%), 7 heart (6.8%), 6 liver (5.8%), and 13 multiorgan (12.6%) transplants. The median age was 54.5 y (interquartile range [IQR], 40.5-65.5) and the median time from transplant to first infection was 6.6 y (IQR, 2.8-11.2). The time between the primary COVID-19 and reinfection was 326 d (IQR, 226-434). Three doses or more of SARS-CoV-2 vaccine are received by 87.4% of patients. After propensity score matching, reinfections were associated with significantly lower hospitalization (5.8% versus 19.4%; risk ratio, 0.3; 95% CI, 0.12-0.71) and oxygen requirement (3.9% versus 13.6%; risk ratio, 0.29; 95% CI, 0.10-0.84). In a within-patient analysis only in the reinfection group, the second infection was milder than the first (3.9% required oxygen versus 19.4%, P < 0.0001), and severe first COVID-19 was the only predictor of severe reinfection. CONCLUSIONS: Transplant recipients with COVID-19 reinfection present better outcomes than those with the first infection, providing clinical evidence for the development of cross-protective immunity.

Risk factors and mortality of SARS-CoV-2 reinfection during the Omicron era in Taiwan: A nationwide population-based cohort study.

BACKGROUND: Prior to 2022, Taiwan had effectively contained the domestic COVID-19 epidemic. However, during 2022, the country encountered multiple large outbreaks of COVID-19, with patients experiencing their first or second infection (reinfection) were both predominantly caused by the Omicron variant. Data are lacking on the risk factors and mortality of COVID-19 reinfection in Omicron era. METHODS: In this retrospective population-based cohort study, we recruited COVID-19 patients with their first episode confirmed between April 1, 2022 and June 11, 2022. A reinfection patient was defined as an individual who infected again by SARS-CoV-2 with an interval of more than 90 days. Demographic characteristics, severity of underlying diseases, and vaccination status were adjusted to identify risk factors for reinfection and to further evaluate the hazard of all-cause mortality within 30 days between reinfection and non-reinfection patients. RESULTS: There were 28,588 reinfection patients matched with 142,940 non-reinfection patients included in this study. We found that being female, younger in age, having more severe underlying diseases, and not being fully vaccinated against COVID-19 were risk factors for reinfection. After adjusting for confounding factors, reinfection patients were at a significantly higher risk of all-cause mortality within 30 days (aHR = 4.29, 95% CI: 3.00-6.12, p < 0.001) comparing with non-reinfection patients. CONCLUSION: During the SARS-CoV-2 Omicron era, reinfection patients were observed to have an increased risk of all-cause mortality. To reduce the disease burden and minimize the risk of reinfection, it is crucial for vulnerable patients to receive full vaccination and adhere to recommended precautions.