Evaluation of disease severity during SARS-COV-2 reinfection, January 2020 to April 2021, England: an observational study

Risk of reinfection and severity with the predominant BA.5 Omicron subvariant China, from December 2022 to January 2023

Data on reinfection in large Asian populations are limited. In this study, we aimed to evaluate the reinfection rate, disease severity, and time interval between the infections in the symptomatic and asymptomatic populations which are firstl infected with BA.2 Omicron Variant. We retrospectively included adult patients with COVID-19 discharged from four designated hospitals between 27 April 2021 and 30 November 2022, who were interviewed via telephone from 29 January to 1 March 2023. Univariable and multivariable analyses were used to explore risk factors associated with reinfection. A total of 16,558 patients were followed up, during the telephone survey of an average of 310.0 days, 1610 (9.72%) participants self-reported reinfection. The mean time range of reinfection was 257.9 days. The risks for reinfection were analysed using multivariable logistic regression. Patients with severe first infection were at higher risk for reinfection (aORs, 2.50; P < 0.001). The male (aORs,0.82; P < 0.001), the elderly (aORs, 0.44; P < 0.001), and patients with full vaccination (aORs, 0.67; P < 0.001) or booster (aORs, 0.63; P < 0.001) had the lower risk of reinfection. Patients over 60 years of age (aORs,9.02; P = 0.006) and those with ≥2 comorbidities (aORs,11.51; P = 0.016). were at higher risk for severe reinfection. The number of clinical manifestations of reinfection increases in people with severe first infection (aORs, 2.82; P = 0.023). The overall reinfection rate was 9.72%, and the reinfection rate of Omicron-to-Omicron subvariants was 9.50% at one year. The severity of Omicron-Omicron reinfection decreased. Data from our clinical study may provide clinical evidence and bolster response preparedness for future COVID-19 reinfection waves.

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.

Changes in sick notes associated with COVID-19 from 2020 to 2022: a cohort study in 24 million primary care patients in OpenSAFELY-TPP

OBJECTIVES

Long-term sickness absence from employment has negative consequences for the economy and can lead to widened health inequalities. Sick notes (also called 'fit notes') are issued by general practitioners when a person cannot work for health reasons for more than 7 days. We quantified the sick note rate in people with evidence of COVID-19 in 2020, 2021 and 2022, as an indication of the burden for people recovering from COVID-19.

DESIGN

Cohort study.

SETTING

With National Health Service (NHS) England approval, we used routine clinical data (primary care, hospital and COVID-19 testing records) within the OpenSAFELY-TPP database.

PARTICIPANTS

People 18-64 years with a recorded positive test or diagnosis of COVID-19 in 2020 (n=365 421), 2021 (n=1 206 555) or 2022 (n=1 321 313); general population matched in age, sex and region in 2019 (n=3 140 326), 2020 (n=3 439 534), 2021 (n=4 571 469) and 2022 (n=4 818 870); people hospitalised with pneumonia in 2019 (n=29 673).

PRIMARY OUTCOME MEASURE

Receipt of a sick note in primary care.

RESULTS

Among people with a positive SARS-CoV-2 test or COVID-19 diagnosis, the sick note rate was 4.88 per 100 person-months (95% CI 4.83 to 4.93) in 2020, 2.66 (95% CI 2.64 to 2.67) in 2021 and 1.73 (95% CI 1.72 to 1.73) in 2022. Compared with the age, sex and region-matched general population, the adjusted HR for receipt of a sick note over the entire follow-up period (up to 10 months) was 4.07 (95% CI 4.02 to 4.12) in 2020 decreasing to 1.57 (95% CI 1.56 to 1.58) in 2022. The HR was highest in the first 30 days postdiagnosis in all years. Among people hospitalised with COVID-19, after adjustment, the sick note rate was lower than in people hospitalised with pneumonia.

CONCLUSIONS

Given the under-recording of postacute COVID-19-related symptoms, these findings contribute a valuable perspective on the long-term effects of COVID-19. Despite likely underestimation of the sick note rate, sick notes were issued more frequently to people with COVID-19 compared with those without, even in an era when most people are vaccinated. Most sick notes occurred in the first 30 days postdiagnosis, but the increased risk several months postdiagnosis may provide further evidence of the long-term impact.

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.

A mini review of reinfection with the SARS-CoV-2 Omicron variant

Background

COVID-19 has caused severe morbidity and mortality worldwide. After the end of the dynamic zero-COVID policy in China in December, 2022, concerns regarding reinfection were raised while little was known due to the lack of surveillance data in this country.

Aims

This study reviews the probability, risk factors, and severity of severe acute respiratory syndrome coronavirus 2 Omicron variant reinfection, as well as the interval between infections, risk of onward transmission by reinfected cases, and the role of booster vaccination against reinfection.

Sources

References for this review were identified through searches of PubMed and Web of Science up to September 24, 2023.

Results

The rate of reinfection ranges from 3.1% to 13.0%. Factors associated with a higher risk of reinfection include being female, having comorbidities, and being unvaccinated. Reinfection with the BA.4 or BA.5 variant occurs approximately 180 days after the initial infection. Reinfections are less clinically severe than primary infections, and there is evidence of lower transmissibility. The debate surrounding the effectiveness and feasibility of booster vaccinations in preventing reinfection continues.

Conclusions

The reinfection rate during the Omicron epidemic is significantly higher than in previous epidemic periods. However, the symptoms and infectivity of reinfection were weaker than those of the prior infection. Medical staff and individuals at high risk of reinfection should be vigilant. The efficacy of booster vaccinations in reducing reinfection is currently under debate.

What Influence Could the Acceptance of Visitors Cause on the Epidemic Dynamics of a Reinfectious Disease?: A Mathematical Model

The globalization in business and tourism becomes crucial more and more for the economical sustainability of local communities. In the presence of an epidemic outbreak, there must be such a decision on the policy by the host community as whether to accept visitors or not, the number of acceptable visitors, or the condition for acceptable visitors. Making use of an SIRI type of mathematical model, we consider the influence of visitors on the spread of a reinfectious disease in a community, especially assuming that a certain proportion of accepted visitors are immune. The reinfectivity of disease here means that the immunity gained by either vaccination or recovery is imperfect. With the mathematical results obtained by our analysis on the model for such an epidemic dynamics of resident and visitor populations, we find that the acceptance of visitors could have a significant influence on the disease's endemicity in the community, either suppressive or supportive.

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.

Impact of vaccination on morbidity and mortality in adults hospitalized with COVID-19 during the omicron wave in the Jazan Region, Saudi Arabia

OBJECTIVES

To evaluate the impact of coronavirus disease-19 (COVID-19) vaccination on morbidity and mortality in adults hospitalized with COVID-19 during the omicron wave in the Jazan Region, Saudi Arabia.

METHODS

A 6-month record-based historical prospective study enrolled COVID-19 adult patients admitted between January and June 2022. Individuals were classified into 3 groups according to their immunity status (immunized, partially immunized, and not immunized). Death, intensive care unit (ICU) admission, and mechanical ventilation were identified as the primary outcomes, collectively referred to as "serious outcomes". On the other hand, the length of hospital stays longer than 5 days was categorized as a secondary outcome. Multiple logistic regression analysis was used to evaluate independent factors and the relationship between the outcomes and vaccination status.

RESULTS

Among the 634 COVID-19 patients admitted to Jazan hospitals, 46.4% were fully immunized, 19.7% were partially immunized, and 33.9% were not immunized. Not being immunized was significantly associated with ICU admission (odds ratio [OR]=1.91, 95% confidence interval [CI]: [1.17-3.11]; p=0.009), mechanical ventilation (OR=2.11, 95% CI: [1.25-3.56]; p=0.005), increased length of hospital stays (OR=1.79, 95% CI: [1.24-2.59]; p=0.002), and death (OR=3.03, 95% CI: [1.85-4.98]; p<0.001).

CONCLUSION

Our study underscores the importance of a comprehensive approach for managing COVID-19 patients that includes vaccination against the disease.

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.

Influence of Prior SARS-CoV-2 Infection on COVID-19 Severity: Evidence from the National COVID Cohort Collaborative

Background

A large share of SARS-CoV-2 infections now occur among previously infected individuals. In this study, we sought to determine whether prior infection modifies disease severity relative to no prior infection.

Methods

We used data from first and second COVID-19 episodes in the National COVID Cohort Collaborative, a nationwide collection of de-identified electronic health records. We used nested logistic regressions of monthly cohorts weighted on the inverse probability of prior infection to assess risk of hospitalization, death, and increased severity in the first versus second infection cohorts.

Results

We included a total of 2,058,274 individuals in the analysis, 147,592 of whom had two recorded infections. The impact of prior infection differed meaningfully between months. Prior infection was largely protective prior to March 2022, with odds ratios (ORs) as low as 0.66 (95% confidence interval: 0.51 to 0.86) in November 2021 for hospitalization. and as low as 0.23 (0.06 to 0.86) in June 2021 for death. However, prior infection was associated with an increased risk of hospitalization and death, mostly after March 2022 when the ORs were as high as 1.87 (1.26 to 2.80) and 2.99 (1.65 to 5.41) in April 2022, respectively. The overall OR for more severe disease was 1.06 (1.03 to 1.10) among previously infected individuals.

Conclusion

In the pandemic's first two years, previously infected patients generally had less severe disease than people without prior infection. During the Omicron era, however, previously infected patients had the same or worse severity of disease as patients without prior 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.

Changes in the intrinsic severity of severe acute respiratory syndrome coronavirus 2 according to the emerging variant: a nationwide study from February 2020 to June 2022, including comparison with vaccinated populations

BACKGROUND

As the population acquires immunity through vaccination and natural infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), understanding the intrinsic severity of coronavirus disease (COVID-19) is becoming challenging. We aimed to evaluate the intrinsic severity regarding circulating variants of SARS-CoV-2 and to compare this between vaccinated and unvaccinated individuals.

METHODS

With unvaccinated and initially infected confirmed cases of COVID-19, we estimated the case severity rate (CSR); case fatality rate (CFR); and mortality rate (MR), including severe/critical cases and deaths, stratified by age and compared by vaccination status according to the period regarding the variants of COVID-19 and vaccination. The overall rate was directly standardized with age.

RESULTS

The age-standardized CSRs (aCSRs) of the unvaccinated group were 2.12%, 5.51%, and 0.94% in the pre-delta, delta, and omicron period, respectively, and the age-standardized CFRs (aCFRs) were 0.60%, 2.49%, and 0.63% in each period, respectively. The complete vaccination group had lower severity than the unvaccinated group over the entire period showing under 1% for the aCSR and 0.5% for the aCFR. The age-standardized MR of the unvaccinated group was 448 per million people per month people in the omicron period, which was 11 times higher than that of the vaccinated group. In terms of age groups, the CSR and CFR sharply increased with age from the 60 s and showed lower risk reduction in the 80 s when the period changed to the omicron period.

CONCLUSIONS

The intrinsic severity of COVID-19 was the highest in the delta period, with over 5% for the aCSR, whereas the completely vaccinated group maintained below 1%. This implies that when the population is vaccinated, the impact of COVID-19 will be limited, even if a new mutation appears. Moreover, considering the decreasing intrinsic severity, the response to COVID-19 should prioritize older individuals at a higher risk of severe disease.

Risk Factors Contributing to Reinfection by SARS-CoV-2: A Systematic Review

This article aims to systematize the evidence regarding risk factors associated with COVID-19 reinfection. We conducted a systematic review of all the scientific publications available until August 2022. To ensure the inclusion of the most recent and relevant information, we searched the PubMed and Scopus databases. Thirty studies were reviewed, with a significant proportion being analytical observational case-control and cohort studies. Upon qualitative analysis of the available evidence, it appears that the probability of reinfection is higher for individuals who are not fully immunized when exposed to a new variant, females, those with pre-existing chronic diseases, individuals aged over 60, and those who have previously experienced severe symptoms of the disease or are immunocompromised. In conclusion, further analytical observational case-control studies are necessary to gain a better understanding of the risk factors associated with SARS-CoV-2 (COVID-19) reinfection.

Neutralization against Omicron subvariants after BA.5/BF.7 breakthrough infection weakened as virus evolution and aging despite repeated prototype-based vaccination1

BACKGROUND

Omicron had swept the mainland China between December 2022 and January 2023, while SARS-CoV-2 still continued to evolve. To fully prepare for the next wave, it's urgent to evaluate the humoral immune response post BA.5/BF.7 breakthrough infection against predominant sub-lineages among existing vaccination strategies and the elders.

METHOD

This study enrolled a longitudinal young-adult cohort from 2/3-dose vaccination to 1 month after breakthrough infection, and an elder cohort at 1 month after breakthrough infection. Seral samples were collected and tested for humoral immune response to SARS-CoV-2 subvariants including WT, BA.2, BA.5, BF.7, BQ.1.1, CH.1.1, XBB.1.5.

RESULTS

BA.5/BF.7 breakthrough infection induced higher neutralization activity than solely vaccination in all SARS-CoV-2 strains, while the latest Omicron subvariants, BQ.1.1, CH.1.1, XBB.1.5, exhibited the strongest neutralization evasion ability. There was a negative correlation between age and humoral immune response in WT, BA.5, BQ.1.1, and XBB.1.5. Compared to non-vaccination groups, breakthrough infection in two-dose vaccination groups had significantly higher neutralizing antibody against WT, BA.2, BA.5, BF.7 but not to BQ.1.1, CH.1.1, XBB.1.5 while booster dose against the prototype prior-breakthrough would not further significantly enhance individual's humoral responses against the latest Omicron subvariants.

CONCLUSIONS

Newer variants manifest increasing immune evasion from neutralization and repeated prototype-based booster vaccines may not further enhance neutralizing antibody against emerging new variants. Older adults have lower levels of neutralizing antibody. Future vaccination strategies should aim to enhance effective neutralization to contemporary variants.

Incidence and outcome of SARS-CoV-2 reinfection in the pre-Omicron era: A global systematic review and meta-analysis

Background

With the emergence of new variants and sub-lineages of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), reinfections can significantly impact herd immunity, vaccination policies, and decisions on other public health measures. We conducted a systematic review and meta-analysis to synthesise the global evidence on SARS-CoV-2 reinfections in the pre-Omicron era.

Methods

We searched five global databases (MEDLINE, Embase, CINAHL Plus, Global Health, WHO COVID-19) on 12 May 2022 and 28 July 2023 and three Chinese databases (CNKI, Wanfang, CQvip) on 16 October 2022 for articles reporting incidence and outcomes of SARS-CoV-2 reinfection before the period of Omicron (B.1.1.529) predominance. We assessed risk of bias using Joanna Briggs Institute critical appraisal tools and conducted meta-analyses with random effects models to estimate the proportion of SARS-CoV-2 reinfection among initially infected cases and hospitalisation and mortality proportions among reinfected ones.

Results

We identified 7593 studies and extracted data from 64 included ones representing 21 countries. The proportion of SARS-CoV-2 reinfection was 1.16% (95% confidence interval (CI) = 1.01-1.33) based on 11 639 247 initially infected cases, with ≥45 days between the two infections. Healthcare providers (2.28%; 95% CI = 1.37-3.40) had a significantly higher risk of reinfection than the general population (1.00%; 95% CI = 0.81-1.20), while young adults aged 18 to 35 years (1.01%; 95% CI = 0.8-1.25) had a higher reinfection burden than other age groups (children <18 years old: 0.57%; 95% CI = 0.39-0.79, older adults aged 36-65 years old: 0.53%; 95% CI = 0.41-0.65, elderly >65 years old: 0.37%; 95% CI = 0.15-0.66). Among the reinfected cases, 8.12% (95% CI = 5.30-11.39) were hospitalised, 1.31% (95% CI = 0.29-2.83) were admitted to the intensive care unit, and 0.71% (95% CI = 0.02-2.01) died.

Conclusions

Our data suggest a relatively low risk of SARS-CoV-2 reinfection in the pre-Omicron era, but the risk of hospitalisation was relatively high among the reinfected cases. Considering the possibility of underdiagnosis, the reinfection burden may be underestimated.

Registration

PROSPERO: CRD42023449712.

Prior SARS-CoV-2 infection may not alter the clinical course of COVID-19 in lung transplant recipients: A single-center experience

BACKGROUND

In the general population, prior infection with SARS-CoV-2 reduces the risk of severe COVID-19; however, studies in lung transplant recipients (LTRs) are lacking. We sought to describe the clinical course of COVID-19 recurrence and compare outcomes between the first and second episodes of COVID-19 in LTRs.

METHODS

We conducted a retrospective, single-center cohort study of LTRs with COVID-19 between January 1, 2022, and September 30, 2022, during the Omicron wave. We compared the clinical course of a second episode of COVID-19 to that of the patients' own first episode and to that of LTRs who developed a first episode during the study period.

RESULTS

During the study period, we identified 24 LTRs with COVID-19 recurrence and another 75 LTRs with a first episode of COVID-19. LTRs who survived the initial episode of COVID-19 had a similar disease course with recurrence, with a trend toward reduced hospitalization (10 (41.6%) vs. 4 (16.7%), p = .114). Furthermore, compared to LTRs with a primary infection during the Omicron wave, those with a reinfection had a non-statistically significant trend toward reduced hospitalizations (aOR .391, 95% CI [.115-1.321], p = .131), shorter lengths-of-stay (median, 4 vs. 9 days, p = .181), and reduced intensive care unit admissions, intubations, and COVID-19-related mortality.

CONCLUSIONS

LTRs who survive the first episode of COVID-19 are likely to have a similar clinical course with recurrent episodes. Although recurrent COVID-19 may be milder, larger, well-powered studies are needed to confirm this observation. Ongoing precautions are warranted.

Risk of SARS-CoV-2 Reinfection 3 Years after the Start of the Pandemic: A Population-Level Observational Study

The risk of SARS-CoV-2 reinfections changes as new variants emerge, but the follow-up time for most of the available evidence is shorter than two years. This study evaluated SARS-CoV-2 reinfection rates in the total population of an Italian province up to three years since the pandemic's start. This retrospective cohort study used official National Healthcare System data on SARS-CoV-2 testing and vaccinations, demographics, and hospitalizations in the Province of Pescara, Italy, from 2 March 2020 to 31 December 2022. A total of 6541 (5.4%) reinfections and 33 severe and 18 lethal COVID-19 cases were recorded among the 121,412 subjects who recovered from a primary infection. There were no severe events following reinfection in the young population, whereas 1.1% of reinfected elderly died. A significantly higher reinfection risk was observed among females; unvaccinated individuals; adults (30-59 y); and subjects with hypertension, COPD, and kidney disease. Up to three years after a primary SARS-CoV-2 infection, the majority of the population did not experience a reinfection. The risk of severe COVID-19 following a reinfection was very low for young and adult individuals but still high for the elderly. The subjects with hybrid immunity showed a lower reinfection risk than the unvaccinated.

Risk Factors Related to COVID-19 Reinfection and Fatality During the Omicron (BA.1/BA.2) Period in Korea

BACKGROUND

This study aimed to investigate the deaths due to coronavirus disease 2019 (COVID-19) reinfection and related risk factors.

METHODS

National cohort data were collected for a six-month period when omicron BA.1/BA.2 variant was dominant in South Korea.

RESULTS

The long-term care facility residents (adjusted odds ratio, 3.11; 95% confidence interval [CI], 2.98-3.25) had significantly higher risk of reinfection than the general population. The risk of reinfection was significantly lower for persons with 2 or more vaccine doses compared to the unvaccinated. The risk of death was significantly higher in the reinfection group than in the primary infection group for persons in the 60-74 years age group (adjusted relative risk [aRR], 1.62; 95% CI, 1.19-2.20), and immunocompromised group (aRR, 4.56; 95% CI, 2.34-8.90).

CONCLUSION

In these data, vaccination history was significantly related to reduced COVID-19 reinfection and severe progression, and scheduled vaccinations were important even with a history of infection.

The Infection of Healthcare Workers and the Reinfection of Patients by Omicron Variant - Jiangsu Province, China, December 2022 to January 2023

What is already known about this topic?

Healthcare workers (HCWs) and previously infected patients (PIPs) may experience a wave of epidemic following the modification of the country's coronavirus disease (COVID)-zero policy in China.

What is added by this report?

As of early January 2023, the initial wave of the COVID-19 pandemic among HCWs had effectively subsided, with no statistically significant differences observed in infection rates compared to those of their co-occupants. The proportion of reinfections among PIPs was relatively low, particularly in those with recent infections.

What are the implications for public health practice?

Medical and health services have resumed normal operations. For patients who have recently experienced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, appropriate relaxation of policies may be considered.

Global prevalence of coronavirus disease 2019 reinfection: a systematic review and meta-analysis

BACKGROUND

In December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged with a high transmissibility rate and resulted in numerous negative impacts on global life. Preventive measures such as face masks, social distancing, and vaccination helped control the pandemic. Nonetheless, the emergence of SARS-CoV-2 variants, such as Omega and Delta, as well as coronavirus disease 2019 (COVID-19) reinfection, raise additional concerns. Therefore, this study aimed to determine the overall prevalence of reinfection on global and regional scales.

METHODS

A systematic search was conducted across three databases, PubMed, Scopus, and ProQuest Central, including all articles pertaining to COVID-19 reinfection without language restriction. After critical appraisal and qualitative synthesis of the identified relevant articles, a meta-analysis considering random effects was used to pool the studies.

RESULTS

We included 52 studies conducted between 2019 and 2022, with a total sample size of 3,623,655 patients. The overall prevalence of COVID-19 reinfection was 4.2% (95% confidence interval [CI]: 3.7-4.8%; n = 52), with high heterogeneity between studies. Africa had the highest prevalence of 4.7% (95% CI: 1.9-7.5%; n = 3), whereas Oceania and America had lower estimates of 0.3% (95% CI: 0.2-0.4%; n = 1) and 1% (95% CI: 0.8-1.3%; n = 7), respectively. The prevalence of reinfection in Europe and Asia was 1.2% (95% CI: 0.8-1.5%; n = 8) and 3.8% (95% CI: 3.4-4.3%; n = 43), respectively. Studies that used a combined type of specimen had the highest prevalence of 7.6% (95% CI: 5.8-9.5%; n = 15) compared with those that used oropharyngeal or nasopharyngeal swabs only that had lower estimates of 6.7% (95% CI: 4.8-8.5%; n = 8), and 3.4% (95% CI: 2.8-4.0%; n = 12) respectively.

CONCLUSION

COVID-19 reinfection occurs with varying prevalence worldwide, with the highest occurring in Africa. Therefore, preventive measures, including vaccination, should be emphasized to ensure control of the pandemic.

Incidence and Risk Factors of the COVID-19 Pandemic: An Epidemiological Approach

After three years of the COVID-19 pandemic, it is certain that the SARS-CoV-2 virus has been a turning point for humanity in both developed and developing countries [...].

SARS-CoV-2 Reinfection and Severity of the Disease: A Systematic Review and Meta-Analysis

Since the discovery of SARS-CoV-2, changes in genotype and reinfection with different variants have been observed in COVID-19-recovered patients, raising questions around the clinical pattern and severity of primary infection and reinfection. In this systematic review, we summarize the results of 23 studies addressing SARS-CoV-2 reinfections. A total of 23,231 reinfected patients were included, with pooled estimated reinfection rates ranging from 0.1 to 6.8%. Reinfections were more prevalent during the Omicron variant period. The mean age of reinfected patients was 38.0 ± 6. years and females were predominant among reinfected patients (M/F = 0.8). The most common symptoms during the first and second infection were fever (41.1%), cough (35.7% and 44.6%), myalgia (34.5% and 33.3%), fatigue (23.8% and 25.6%), and headaches (24.4% and 21.4%). No significant differences of clinical pattern were observed between primary infection and reinfection. No significant differences in the severity of infection were observed between primary infection and reinfection. Being female, being a patient with comorbidities, lacking anti-nucleocapsid IgG after the first infection, being infected during the Delta and Omicron wave, and being unvaccinated were associated with a higher risk of reinfection. Conflicting age-related findings were found in two studies. Reinfection with SARS-CoV-2 suggests that natural immunity is not long-lasting in COVID-19 patients.

Effectiveness of Molnupiravir and Nirmatrelvir-Ritonavir in Hospitalized Patients With COVID-19 : A Target Trial Emulation Study

BACKGROUND

Whether hospitalized patients benefit from COVID-19 oral antivirals is uncertain.

OBJECTIVE

To examine the real-world effectiveness of molnupiravir and nirmatrelvir-ritonavir in hospitalized patients with COVID-19 during the Omicron outbreak.

DESIGN

Target trial emulation study.

SETTING

Electronic health databases in Hong Kong.

PARTICIPANTS

The molnupiravir emulated trial included hospitalized patients with COVID-19 aged 18 years or older between 26 February and 18 July 2022 (n = 16 495). The nirmatrelvir-ritonavir emulated trial included hospitalized patients with COVID-19 aged 18 years or older between 16 March and 18 July 2022 (n = 7119).

INTERVENTION

Initiation of molnupiravir or nirmatrelvir-ritonavir within 5 days of hospitalization with COVID-19 versus no initiation of molnupiravir or nirmatrelvir-ritonavir.

MEASUREMENTS

Effectiveness against all-cause mortality, intensive care unit (ICU) admission, or use of ventilatory support within 28 days.

RESULTS

The use of oral antivirals in hospitalized patients with COVID-19 was associated with a lower risk for all-cause mortality (molnupiravir: hazard ratio [HR], 0.87 [95% CI, 0.81 to 0.93]; nirmatrelvir-ritonavir: HR, 0.77 [CI, 0.66 to 0.90]) but no significant risk reduction in terms of ICU admission (molnupiravir: HR, 1.02 [CI, 0.76 to 1.36]; nirmatrelvir-ritonavir: HR, 1.08 [CI, 0.58 to 2.02]) or the need for ventilatory support (molnupiravir: HR, 1.07 [CI, 0.89 to 1.30]; nirmatrelvir-ritonavir: HR, 1.03 [CI, 0.70 to 1.52]). There was no significant interaction between drug treatment and the number of COVID-19 vaccine doses received, thereby supporting the effectiveness of oral antivirals regardless of vaccination status. No significant interaction between nirmatrelvir-ritonavir treatment and age, sex, or Charlson Comorbidity Index was observed, whereas molnupiravir tended to be more effective in older people.

LIMITATION

The outcome of ICU admission or need for ventilatory support may not capture all severe COVID-19 cases; unmeasured confounders, such as obesity and health behaviors, may exist.

CONCLUSION

Molnupiravir and nirmatrelvir-ritonavir reduced all-cause mortality in both vaccinated and unvaccinated hospitalized patients. No significant reduction in ICU admission or the need for ventilatory support was observed.

PRIMARY FUNDING SOURCE

Health and Medical Research Fund Research on COVID-19, Government of the Hong Kong Special Administrative Region; Research Grants Council, Collaborative Research Fund; and Health Bureau, Government of the Hong Kong Special Administrative Region.

Development and external validation of prediction models for critical outcomes of unvaccinated COVID-19 patients based on demographics, medical conditions and dental status

Background

Multiple prediction models were developed for critical outcomes of COVID-19. However, prediction models using predictors which can be easily obtained in clinical practice and on dental status are scarce.

Aim

The study aimed to develop and externally validate prediction models for critical outcomes of COVID-19 for unvaccinated adult patients in hospital settings based on demographics, medical conditions, and dental status.

Methods

A total of 285 and 352 patients from two hospitals in the Netherlands were retrospectively included as derivation and validation cohorts. Demographics, medical conditions, and dental status were considered potential predictors. The critical outcomes (death and ICU admission) were considered endpoints. Logistic regression analyses were used to develop two models: for death alone and for critical outcomes. The performance and clinical values of the models were determined in both cohorts.

Results

Age, number of teeth, chronic kidney disease, hypertension, diabetes, and chronic obstructive pulmonary diseases were the significant independent predictors. The models showed good to excellent calibration with observed: expected (O:E) ratios of 0.98 (95%CI: 0.76 to 1.25) and 1.00 (95%CI: 0.80 to 1.24), and discrimination with shrunken area under the curve (AUC) values of 0.85 and 0.79, based on the derivation cohort. In the validation cohort, the models showed good to excellent discrimination with AUC values of 0.85 (95%CI: 0.80 to 0.90) and 0.78 (95%CI: 0.73 to 0.83), but an overestimation in calibration with O:E ratios of 0.65 (95%CI: 0.49 to 0.85) and 0.67 (95%CI: 0.52 to 0.84).

Conclusion

The performance of the models was acceptable in both derivation and validation cohorts. Number of teeth was an additive important predictor of critical outcomes of COVID-19. It is an easy-to-apply tool in hospitals for risk stratification of COVID-19 prognosis.

Oral Nirmatrelvir and Ritonavir in Nonhospitalized Vaccinated Patients With Coronavirus Disease 2019

BACKGROUND

Treatment of coronavirus disease 2019 (COVID-19) with nirmatrelvir plus ritonavir (NMV-r) in high-risk nonhospitalized unvaccinated patients reduced the risk of progression to severe disease. However, the potential benefits of NMV-r among vaccinated patients are unclear.

METHODS

We conducted a comparative retrospective cohort study using the TriNetX research network. Patients ≥18 years of age who were vaccinated and subsequently developed COVID-19 between 1 December 2021 and 18 April 2022 were included. Cohorts were developed based on the use of NMV-r within 5 days of diagnosis. The primary composite outcome was all-cause emergency room (ER) visit, hospitalization, or death at a 30-day follow-up. Secondary outcomes included individual components of primary outcomes, multisystem symptoms, COVID-19-associated complications, and diagnostic test utilization.

RESULTS

After propensity score matching, 1130 patients remained in each cohort. A primary composite outcome of all-cause ER visits, hospitalization, or death in 30 days occurred in 89 (7.87%) patients in the NMV-r cohort compared with 163 (14.4%) patients in the non-NMV-r cohort (odds ratio: .5; 95% confidence interval: .39-.67; P < .005) consistent with 45% relative risk reduction. A significant reduction in multisystem symptom burden and subsequent complications, such as lower respiratory tract infection, cardiac arrhythmia, and diagnostic radiology testing, were noted in NMV-r-treated patients. There was no apparent increase in serious complications between days 10 and 30.

CONCLUSIONS

Treatment with NMV-r in nonhospitalized vaccinated patients with COVID-19 was associated with a reduced likelihood of ER visits, hospitalization, or death. Complications and overall resource utilization were also decreased.

Severity and Outcomes of SARS-CoV-2 Reinfection Compared with Primary Infection: A Systematic Review and Meta-Analysis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection has brought new challenges to the global prevention and control of coronavirus disease 2019 (COVID-19) pandemic; however, current studies suggest that there is still great uncertainty about the risk of severe COVID-19 and poor outcomes after SARS-CoV-2 reinfection. Random-effects inverse-variance models were used to evaluate the pooled prevalence (PP) and its 95% confidence interval (CI) of severity, outcomes and symptoms of reinfection. Random-effects were used to estimate the pooled odds ratios (OR) and its 95%CI of severity and outcomes between reinfections and primary infections. Nineteen studies involving a total of 34,375 cases of SARS-CoV-2 reinfection and 5,264,720 cases of SARS-CoV-2 primary infection were included in this meta-analysis. Among those SARS-CoV-2 reinfection cases, 41.77% (95%CI, 19.23-64.31%) were asymptomatic, and 51.83% (95%CI, 23.90-79.76%) were symptomatic, only 0.58% (95%CI, 0.031-1.14%) manifested as severe illness, and 0.04% (95%CI, 0.009-0.078%) manifested as critical illness. The PPs for SARS-CoV-2 reinfection-related hospitalization, admission to ICU, and death were, respectively, 15.48% (95%CI, 11.98-18.97%), 3.58% (95%CI, 0.39-6.77%), 2.96% (95%CI, 1.25-4.67%). Compared with SARS-CoV-2 primary infection cases, reinfection cases were more likely to present with mild illness (OR = 7.01, 95%CI, 5.83-8.44), and the risk of severe illness was reduced by 86% (OR = 0.14, 95%CI, 0.11-0.16). Primary infection provided some protection against reinfection and reduces the risk of symptomatic infection and severe illness. Reinfection did not contribute to extra risk of hospitalization, ICU, or death. It is suggested to scientifically understand the risk of reinfection of SARS-CoV-2, strengthen public health education, maintain healthy habits, and reduce the risk of reinfection.

T-Cell Immunity in COVID-19-Recovered Individuals and Individuals Vaccinated with the Combined Vector Vaccine Gam-COVID-Vac

The COVID-19 pandemic has required extensive research on the new coronavirus SARS-CoV-2 and the creation of new highly effective vaccines. The presence of T-cells in the body that respond to virus antigens suggests adequate antiviral immunity. We investigated T-cell immunity in individuals who recovered from mild and moderate COVID-19 and in individuals vaccinated with the Gam-COVID-Vac combined vector vaccine. The ELISPOT method was used to determine the number of T-cells responding with IFN-γ synthesis to stimulation by peptides containing epitopes of the S-protein or N-, M-, ORF3, and ORF7 proteins, using peripheral blood mononuclear cells (PBMCs). At the same time, the multiplex method was used to determine the accumulation of IFN-γ and other cytokines in the culture medium. According to the data obtained, the proportion of positive conclusions about the T-cell immune response to SARS-CoV-2 antigens in control, recovered, and vaccinated individuals was 12%, 70%, and 52%, respectively. At the same time, more than half of the vaccinated individuals with a T-cell response were sensitized to the antigens of N-, M-, ORF3, and ORF7 proteins not produced by Gam-COVID-Vac, indicating a high likelihood of asymptomatic SARS-CoV-2 infection. Increased IFN-γ release by single sensitized T-cells in response to specific stimulation in recovered and vaccinated individuals did not result in the accumulation of this and other cytokines in the culture medium. These findings suggest a balance between cytokine production and utilization by immunocompetent cells as a prerequisite for providing a controlled cytokine signal and avoiding a "cytokine storm".

Risk Factors of Severe COVID-19: A Review of Host, Viral and Environmental Factors

The clinical course and outcome of COVID-19 are highly variable, ranging from asymptomatic infections to severe disease and death. Understanding the risk factors of severe COVID-19 is relevant both in the clinical setting and at the epidemiological level. Here, we provide an overview of host, viral and environmental factors that have been shown or (in some cases) hypothesized to be associated with severe clinical outcomes. The factors considered in detail include the age and frailty, genetic polymorphisms, biological sex (and pregnancy), co- and superinfections, non-communicable comorbidities, immunological history, microbiota, and lifestyle of the patient; viral genetic variation and infecting dose; socioeconomic factors; and air pollution. For each category, we compile (sometimes conflicting) evidence for the association of the factor with COVID-19 outcomes (including the strength of the effect) and outline possible action mechanisms. We also discuss the complex interactions between the various risk factors.

Patterns of reported infection and reinfection of SARS-CoV-2 in England

One of the key features of any infectious disease is whether infection generates long-lasting immunity or whether repeated reinfection is common. In the former, the long-term dynamics are driven by the birth of susceptible individuals while in the latter the dynamics are governed by the speed of waning immunity. Between these two extremes a range of scenarios is possible. During the early waves of SARS-CoV-2, the underlying paradigm was for long-lasting immunity, but more recent data and in particular the 2022 Omicron waves have shown that reinfection can be relatively common. Here we investigate reported SARS-CoV-2 cases in England, partitioning the data into four main waves, and consider the temporal distribution of first and second reports of infection. We show that a simple low-dimensional statistical model of random (but scaled) reinfection captures much of the observed dynamics, with the value of this scaling, k, providing information of underlying epidemiological patterns. We conclude that there is considerable heterogeneity in risk of reporting reinfection by wave, age-group and location. The high levels of reinfection in the Omicron wave (we estimate that 18% of all Omicron cases had been previously infected, although not necessarily previously reported infection) point to reinfection events dominating future COVID-19 dynamics. This manuscript was submitted as part of a theme issue on "Modelling COVID-19 and Preparedness for Future Pandemics".

How and when to manage respiratory infections out of hospital

Lower respiratory infections include acute bronchitis, influenza, community-acquired pneumonia, acute exacerbation of COPD and acute exacerbation of bronchiectasis. They are a major cause of death worldwide and often affect the most vulnerable: children, elderly and the impoverished. In this paper, we review the clinical presentation, diagnosis, severity assessment and treatment of adult outpatients with lower respiratory infections. The paper is divided into sections on specific lower respiratory infections, but we also dedicate a section to COVID-19 given the importance of the ongoing pandemic. Lower respiratory infections are heterogeneous entities, carry different risks for adverse events, and require different management strategies. For instance, while patients with acute bronchitis are rarely admitted to hospital and generally do not require antimicrobials, approximately 40% of patients seen for community-acquired pneumonia require admission. Clinicians caring for patients with lower respiratory infections face several challenges, including an increasing population of patients with immunosuppression, potential need for diagnostic tests that may not be readily available, antibiotic resistance and social aspects that place these patients at higher risk. Management principles for patients with lower respiratory infections include knowledge of local surveillance data, strategic use of diagnostic tests according to surveillance data, and judicious use of antimicrobials.

Who Is at Higher Risk of SARS-CoV-2 Reinfection? Results from a Northern Region of Italy

The SARS-CoV-2 pandemic continues to spread worldwide, generating a high impact on healthcare systems. The aim of the study was to examine the epidemiological burden of SARS-CoV-2 reinfections and to identify potential related risk factors. A retrospective observational study was conducted in Liguria Region, combining data from National Vaccines Registry and Regional Chronic Condition Data Warehouse. In the study period (September 2021 to May 2022), 335,117 cases of SARS-CoV-2 infection were recorded in Liguria, of which 15,715 were reinfected once. During the Omicron phase (which predominated from 3 January 2022), the risk of reinfection was 4.89 times higher (p < 0.001) than during the Delta phase. Unvaccinated and vaccinated individuals with at least one dose for more than 120 days were at increased risk of reinfection compared with vaccinated individuals with at least one dose for ≤120 days, respectively (odds ratio (OR) of 1.26, p < 0.001; OR of 1.18, p < 0.001). Healthcare workers were more than twice as likely to be reinfected than non-healthcare workers (OR of 2.38, p < 0.001). Lower ORs were seen among people aged 60 to 79 years. Two doses or more of vaccination were found to be protective against the risk of reinfection rather than a single dose (mRNA vaccines: OR of 0.06, p < 0.0001, and OR of 0.1, p < 0.0001; vector vaccines: OR of 0.05, p < 0.0001). Patients with chronic renal failure, cardiovascular disease, bronchopneumopathy, neuropathy and autoimmune diseases were at increased risk of reinfection (OR of 1.38, p = 0.0003; OR of 1.09, p < 0.0296; OR of 1.14, p = 0.0056; OR of 1.78, p < 0.0001; OR of 1.18, p = 0.0205). Estimating the epidemiological burden of SARS-CoV-2 reinfections and the role played by risk factors in reinfections is relevant for identifying risk-based preventive strategies in a pandemic context characterized by a high circulation of the virus and a high rate of pathogen mutations.

Rapid Increase in Suspected SARS-CoV-2 Reinfections, Clark County, Nevada, USA, December 2021

Genetic differences between SARS-CoV-2 variants raise concerns about reinfection. Public health authorities monitored the incidence of suspected reinfection in Clark County, Nevada, USA, during March 2020-March 2022. Suspected reinfections, defined as a second positive PCR test collected >90 days after an initial positive test, were monitored through an electronic disease surveillance system. We calculated the proportion of all new cases per week that were suspected reinfections and rates per 1,000 previously infected persons by demographic groups. The rate of suspected reinfection remained <2.7% until December 2021, then increased to ≈11%, corresponding with local Omicron variant detection. Reinfection rates were higher among adults 18-50 years of age, women, and minority groups, especially persons identifying as American Indian/Alaska Native. Suspected reinfection became more common in Clark County after introduction of the Omicron variant, and some demographic groups are disproportionately affected. Public health surveillance could clarify the SARS-CoV-2 reinfection burden in communities.

Comparative Assessment of Severe Acute Respiratory Syndrome Coronavirus 2 Variants in the Ferret Model

The continued spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in humans necessitates evaluation of variants for enhanced virulence and transmission. We used the ferret model to perform a comparative analysis of four SARS-CoV-2 strains, including an early pandemic isolate from the United States (WA1), and representatives of the Alpha, Beta, and Delta lineages. While Beta virus was not capable of pronounced replication in ferrets, WA1, Alpha, and Delta viruses productively replicated in the ferret upper respiratory tract, despite causing only mild disease with no overt histopathological changes. Strain-specific transmissibility was observed; WA1 and Delta viruses transmitted in a direct contact setting, whereas Delta virus was also capable of limited airborne transmission. Viral RNA was shed in exhaled air particles from all inoculated animals but was highest for Delta virus. Prior infection with SARS-CoV-2 offered varied protection against reinfection with either homologous or heterologous variants. Notable genomic variants in the spike protein were most frequently detected following WA1 and Delta virus infection.

Risk and severity of SARS-CoV-2 reinfections during 2020–2022 in Vojvodina, Serbia: A population-level observational study

Background

Data on the rate and severity of SARS-CoV-2 reinfections in real-world settings are scarce and the effects of vaccine boosters on reinfection risk are unknown.

Methods

In a population-level observational study, registered SARS-CoV-2 laboratory-confirmed Vojvodina residents, between March 6, 2020 and October 31, 2021, were followed for reinfection ≥90 days after primary infection. Data were censored at the end of follow-up (January 31, 2022) or death. The reinfection risk was visualized with Kaplan-Meier plots. To examine the protective effect of vaccination, the subset of individuals with primary infection in 2020 (March 6–December 31) were matched (1:2) with controls without reinfection.

Findings

Until January 31, 2022, 13,792 reinfections were recorded among 251,104 COVID-19 primary infections (5.49%). Most reinfections (86.77%, 11,967/13,792) were recorded in January 2022. Reinfections were mostly mild (99.17%, 13,678/13,792). Hospitalizations were uncommon [1.08% (149/13,792) vs. 3.66% (505/13,792) in primary infection] and COVID-19 deaths were very rare (20/13,792, case fatality rate 0.15%). The overall incidence rate of reinfections was 5.99 (95% CI 5.89–6.09) per 1000 person-months. The reinfection risk was estimated as 0.76% at six months, 1.36% at nine months, 4.96% at 12 months, 16.68% at 15 months, and 18.86% at 18 months. Unvaccinated (OR=1.23; 95%CI=1.14–1.33), incompletely (OR=1.33; 95%CI=1.08–1.64) or completely vaccinated (OR=1.50; 95%CI=1.37–1.63), were modestly more likely to be reinfected compared with recipients of a third (booster) vaccine dose.

Interpretation

SARS-CoV-2 reinfections were uncommon until the end of 2021 but became common with the advent of Omicron. Very few reinfections were severe. Boosters may modestly reduce reinfection risk.

Funding

No specific funding was obtained for this study.

Measuring T-Cell Responses against SARS-CoV-2 Is of Utility for Disease and Vaccination Management

The measurement of specific T-cell responses can be a useful tool for COVID-19 diagnostics and clinical management. In this study, we evaluated the IFN-γ T-cell response against the main SARS-CoV-2 antigens (spike, nucleocapsid and membrane) in acute and convalescent individuals classified according to severity, and in vaccinated and unvaccinated controls. IgG against spike and nucleocapsid were also measured. Spike antigen triggered the highest number of T-cell responses. Acute patients showed a low percentage of positive responses when compared to convalescent (71.6% vs. 91.7%, respectively), but increased during hospitalization and with severity. Some convalescent patients showed an IFN-γ T-cell response more than 200 days after diagnosis. Only half of the vaccinated individuals displayed an IFN-γ T-cell response after the second dose. IgG response was found in a higher percentage of individuals compared to IFN-γ T-cell responses, and moderate correlations between both responses were seen. However, in some acute COVID-19 patients specific T-cell response was detected, but not IgG production. We found that the chances of an IFN-γ T-cell response against SARS-CoV-2 is low during acute phase, but may increase over time, and that only half of the vaccinated individuals had an IFN-γ T-cell response after the second dose.

Clinical Characteristics and Implications of Bradycardia in COVID-19 Patients Treated with Remdesivir: A Single-Center Retrospective Cohort Study

Background and Objectives

Remdesivir is an antiviral drug used to treat coronavirus disease 2019 (COVID-19) with a relatively obscure cardiac effect profile. Previous studies have reported bradycardia associated with remdesivir, but few have examined its clinical characteristics. The objective of this study was to investigate remdesivir associated bradycardia and its associated clinical characteristics and outcomes.

Methods

This is a single-institution retrospective study that investigated bradycardia in 600 patients who received remdesivir for treatment of COVID-19. A total of 375 patients were included in the study after screening for other known causes of bradycardia (atrioventricular [AV] nodal blockers). All patients were analyzed for episodes of bradycardia from when remdesivir was initiated up to 5 days after completion, a time frame based on the drug’s putative elimination half-life. Univariate and multivariate statistical tests were conducted to analyze the data.

Results

The mean age of the sample was 56.63 ± 13.23 years. Of patients who met inclusion criteria, 49% were found to have bradycardia within 5 days of remdesivir administration. Compared to the cohort without a documented bradycardic episode, patients with bradycardia were significantly more likely to experience inpatient mortality (22% vs 12%, p = 0.01). The patients with bradycardia were found to have marginally higher serum D-dimer levels (5.2 vs 3.4 µg/mL, p = 0.05) and were more likely to undergo endotracheal intubation (28% vs 14%, p = 0.008). Male sex, hyperlipidemia, and bradycardia within 5 days of completing remdesivir were significant predictors of inpatient mortality. No significant differences in length of stay were found.

Conclusions

Bradycardia that occurs during or shortly after remdesivir treatment in COVID-19 patients may be associated with an increased rate of in-hospital mortality. However, COVID-19 and its cardiac complications cannot be excluded as potential contributors of bradycardia in the present study. Future studies are needed to further delineate the cardiac characteristics of COVID-19 and remdesivir.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40261-022-01187-x.

Lower Levels of ABO Anti-A and Anti-B of IgM, IgG and IgA Isotypes in the Serum but Not the Saliva of COVID-19 Convalescents

Individuals with ABO type O, naturally possessing anti-A and anti-B antibodies in their serum, are underrepresented among patients infected with SARS-CoV-2 compared with healthy controls. The ABO antibodies might play a role in the viral transmission. Therefore, we aimed to quantify anti-A/anti-B, including their subclasses IgM, IgG and IgA, in the serum and saliva of Caucasians (n = 187) after mild COVID-19 to compare them with individuals who had never been infected with SARS-CoV-2. Two samples were collected within two months after the diagnosis (median days: 44) and two months later. ABO antibodies were determined by flow cytometry. Additionally, total IgA in saliva and antibodies specific to SARS-CoV-2 were tested by ELISA. COVID-19 convalescents had significantly lower levels of anti-A/anti-B IgM, IgG and IgA in their serum than control subjects (p < 0.001). Interestingly, no significant differences were observed in saliva. ABO antibody levels remained stable over the period considered. No relation of ABO to the level of SARS-CoV-2-specific antibodies was observed. Total IgA was lower in convalescents than in controls (p = 0.038). Whereas ABO antibodies in the saliva may not contribute to the pathogenesis of COVID-19, individual pre-existing high serum concentrations of anti-A/anti-B may have a protective effect against SARS-CoV-2 infection.

Protective effect of a first SARS-CoV-2 infection from reinfection: a matched retrospective cohort study using PCR testing data in England

The duration of immunity after first severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the extent to which prior immunity prevents reinfection is uncertain and remains an important question within the context of new variants. This is a retrospective population-based matched observational study where we identified the first polymerase chain reaction (PCR) positive of primary SARS-CoV-2 infection case tests between 1 March 2020 and 30 September 2020. Each case was matched by age, sex, upper tier local authority of residence and testing route to one individual testing negative in the same week (controls) by PCR. After a 90-day pre-follow-up period for cases and controls, any subsequent positive tests up to 31 December 2020 and deaths within 28 days of testing positive were identified, this encompassed an essentially vaccine-free period. We used a conditional logistic regression to analyse the results. There were 517 870 individuals in the matched cohort with 2815 reinfection cases and 12 098 first infections. The protective effect of a prior SARS-CoV-2 PCR-positive episode was 78% (odds ratio (OR) 0.22, 0.21-0.23). Protection rose to 82% (OR 0.18, 0.17-0.19) after a sensitivity analysis excluded 933 individuals with a first test between March and May and a subsequent positive test between June and September 2020. Amongst individuals testing positive by PCR during follow-up, reinfection cases had 77% lower odds of symptoms at the second episode (adjusted OR 0.23, 0.20-0.26) and 45% lower odds of dying in the 28 days after reinfection (adjusted OR 0.55, 0.42-0.71). Prior SARS-CoV-2 infection offered protection against reinfection in this population. There was some evidence that reinfections increased with the alpha variant compared to the wild-type SARS-CoV-2 variant highlighting the importance of continued monitoring as new variants emerge.

Clinical and Biochemical Characteristics of COVID-19 in a Primary Care Center in the South Batinah Region of Oman

Objectives

The main purpose of this study was to identify the clinical and biochemical profile of coronavirus disease 2019 (COVID-19) and sex differences in Rustaq Polyclinic in South Batinah Governorate.

Methods

This study is a retrospective chart review of COVID-19 patients diagnosed in Rustaq Polyclinic in the South Batinah region of Oman. The medical charts of 150 patients from November 10, 2020, to November 24, 2021, at Rustaq Polyclinic were retrospectively reviewed, and clinical and laboratory parameters were extracted. Information regarding the patients’ demographics, risk factors, clinical symptoms or signs, and laboratory findings on admission were obtained. Statistical analysis was performed using the Statistical Package for Social Sciences (SPSS) software version 24.0 (IBM Corp., Armonk, NY, USA).

Results

A total of 150 study participant data were added to the analysis. Of those, 97 (64.7%) were male and 53 (35.3%) were female, with a median age of 32 and 39 among males and females, respectively. Male and female age (p=0.017) and marital status (p=0.003) were significantly different. No significant difference (p≥0.05) was observed between male and female study participants regarding their history of travel, history of contact with COVID-19-positive patients, diabetes, hypertension, stroke, and home management. Similarly, no significant difference (p≥0.05) was observed between males and females regarding their clinical presentations.

Conclusion

Many symptomatic patients have shown influenza-like symptoms such as fever, respiratory symptoms such as cough, sore throat, headache, myalgia, and loss of smell. The spectrum of symptomatic infection ranges from mild to severe, and most infections are not severe. It is imperative to equip ourselves with adequate understanding and protective measures such as vaccination and diverse treatment modalities against the constantly changing nature of novel coronaviruses.