Risk and protective factors for SARS-CoV-2 reinfections, surveillance data, Italy, August 2021 to March 2022

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.

Immune responses and reinfection of SARS-CoV-2 Omicron variant in patients with lung cancer

A significant Omicron wave emerged in China in December 2022. To explore the duration of humoral and cellular response postinfection and the efficacy of hybrid immunity in preventing Omicron reinfection in patients with lung cancer, a total of 447 patients were included in the longitudinal study after the Omicron wave from March 2023 to August 2023. Humoral responses were measured at pre-Omicron wave, 3 months and 7 months postinfection. The detected severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibodies including total antibodies, anti-receptor binding domain (RBD) specific IgG, and neutralizing antibodies against SARS-CoV-2 wild type (WT) and BA.4/5 variant. T cell responses against SARS-CoV-2 WT and Omicron variant were evaluated in 101 patients by ELISpot at 3 months postinfection. The results showed that Omicron-infected symptoms were mild, while fatigue (30.2%), shortness of breath (34.0%) and persistent cough (23.6%) were long-lasting, and vaccines showed efficacy against fever in lung cancer patients. Humoral responses were higher in full or booster vaccinated patients than those unvaccinated (p < .05 for all four antibodies), and the enhanced response persisted for at least 7 months. T cell response to Omicron was higher than WT peptides (21.3 vs. 16.0 SFUs/106 PBMCs, p = .0093). Moreover, 38 (9.74%) patients were reinfected, which had lower antibody responses than non-reinfected patients (all p < .05), and those patients of unvaccinated at late stage receiving anti-cancer immunotherapy alone were at high risk of reinfection. Collectively, these data demonstrate the Omicron infection induces a high and durable immune response in vaccinated patients with lung cancer, which protects vaccinated patients from reinfection.

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 for progression to severe infection and prolonged viral clearance time in hospitalized elderly patients infected with the Omicron variant of SARS-CoV-2: a retrospective study at Shanghai Fourth People's Hospital, School of Medicine, Tongji University

Introduction

In elderly patients infected with the Omicron variant, disease progression to severe infection can result in poor outcomes. This study aimed to identify risk and protective factors associated with disease progression to severe infection and viral clearance time in elderly Omicron-infected patients.

Methods

Shanghai Fourth People's Hospital, School of Medicine, Tongji University, was officially designated to provide treatment to patients with COVID-19. This study was conducted on confirmed Omicron cases admitted to the hospital between 10 April 2022 and 21 June 2022. In total, 1,568 patients aged 65 years or older were included. We conducted a retrospective, observational study using logistic regression to analyze risk and protective factors for the development of severe disease and Cox proportional hazards regression models to analyze factors influencing viral clearance time.

Results

Aged over 80 years, having 2 or more comorbidities, combined cerebrovascular disease, chronic neurological disease, and mental disorders were associated with the development of severe disease, and full vaccination was a protective factor. Furthermore, aged over 80 years, combined chronic respiratory disease, chronic renal disease, cerebrovascular disease, mental disorders, and high viral load were associated with prolonged viral clearance time, and full vaccination was a protective factor.

Discussion

This study analyzed risk factors for progression to severe infection and prolonged viral clearance time in hospitalized elderly Omicron-infected patients. Aged patients with comorbidities had a higher risk of developing severe infection and had longer viral clearance, while vaccination protected them against the Omicron infection.

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.

SARS-CoV-2 Reinfection Cases in a Household-Based Prospective Cohort in Rio de Janeiro

This was a household-based prospective cohort study conducted in Rio de Janeiro, in which people with laboratory-confirmed coronavirus disease 2019 (COVID-19) and their household contacts were followed from April 2020 through June 2022. Ninety-eight reinfections were identified, with 71 (72.5%) confirmed by genomic analyses and lineage definition in both infections. During the pre-Omicron period, 1 dose of any COVID-19 vaccine was associated with a reduced risk of reinfection, but during the Omicron period not even booster vaccines had this effect. Most reinfections were asymptomatic or milder in comparison with primary infections, a justification for continuing active surveillance to detect infections in vaccinated individuals. Our findings demonstrated that vaccination may not prevent infection or reinfection with severe acute respiratory syndrome coronavirus 2 (SARS CoV-2). Therefore we highlight the need to continuously update the antigenic target of SARS CoV-2 vaccines and administer booster doses to the population regularly, a strategy well established in the development of vaccines for influenza immunization programs.

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.

Investigating mortality trends in Italy during the COVID-19 pandemic: life expectancy changes within provinces and vaccination campaign impact up to December 2022

OBJECTIVES

We used publicly available population data from 1 January 2019 up to 31 December 2022, to investigate mortality trends in Italy during the COVID-19 pandemic, evaluating changes in life expectancy (LE) at birth within provinces and the impact of COVID-19 vaccinations.

STUDY DESIGN

Aggregate data analysis.

METHODS

Annual period life tables were used to estimate sex-specific LEs within provinces from 2019 to 2022. We used Arriaga decomposition to analyze the contribution of age groups (<60 years and ≥60 years) to annual LE changes. We implemented a Quasi-Poisson regression model to estimate the number of averted deaths by the achieved COVID-19 vaccination rates from January 2021 up to December 2022, simulating a counterfactual scenario where vaccine doses were not administered.

RESULTS

The results revealed geographical heterogeneity in annual LE changes across Italian provinces during the pandemic. By the end of 2022, LE was below the prepandemic levels in 88% of provinces for females and in 76% for males. In addition, we estimated that the achieved vaccination rates averted 460,831 deaths (95% confidence interval: 250,976-707,920), corresponding to a 25% reduction in expected all-cause mortality.

CONCLUSIONS

Overall, the study highlighted the significant role of COVID-19 vaccinations in averting a considerable number of deaths and improving LE. However, by the end of 2022, LE had not fully recovered to prepandemic levels in many provinces. This could be attributed to concurrent factors, including enduring COVID-19 pandemic effects, intense summer heat waves and early onset of seasonal flu. Further research and continuous monitoring are essential to fully comprehend long-term mortality trends and optimize public health strategies.

Reinfection rates, change in antibody titers and adverse events after COVID-19 vaccination among patients previously infected with COVID-19 in Metro Manila, Philippines: a secondary analysis of a completed cohort study

BACKGROUND

Variation in immune response to COVID-19 vaccines is observed among different ethnicities. We aimed to describe the reinfection rates, change in antibody titers, and adverse events among Filipinos.

METHODS

This is a secondary analysis of a cohort study of 307 participants within one year of having COVID-19 infection. We measured COVID-19 antibody levels at pre-determined timepoints (Days 21, 90, 180, 270, and 360 from initial infection). We monitored for COVID-19 symptoms and obtained details on COVID-19 vaccination. An adjudication committee classified the participants as probable, possible, or unlikely COVID-19 reinfection. We determined the probable reinfection rate, adverse events, and the geometric mean titer (GMT) ratio of pre- and post-vaccination antibody levels according to type and brand of COVID-19 vaccine.

RESULTS

At the end of the follow-up period, 287 (93.5%) out of 307 study participants were fully vaccinated, 1 was partially vaccinated (0.3%), and 19 were unvaccinated (6.2%). Among the fully vaccinated participants, those given mRNA vaccines had the lowest reinfection rate (19.2 cases/100 person-years, 95% CI 9.6, 38.4), followed by viral vector vaccines (29.8 cases/100 person-years, 95% CI 16.9, 52.4). We observed the highest reinfection rate among those given inactivated virus vaccines (32.7 cases/100 person-years, 95% CI 23.6, 45.3). The reinfection rate was 8.6 cases/100 person-years (95% CI 4.1, 17.9) for unvaccinated participants and 3.6 cases/100 person-years (95% CI 0.5, 25.3) for partially vaccinated participants. We observed the largest rise in antibody titers among those given mRNA vaccines (GMT ratio 288.5), and the smallest rise among those given inactivated virus vaccines (GMT ratio 16.7). We observed the highest percentage of adverse events following immunization with viral vector vaccines (63.8%), followed by mRNA vaccines (62.7%), and the lowest for inactivated virus vaccines (34.7%). No serious adverse events were reported.

CONCLUSION

Vaccinees given the mRNA vaccines had the lowest reinfection rate and the highest rise in antibody titers. Vaccinees given inactivated virus vaccines had the highest reinfection rate, smallest rise in antibody titers, and lowest percentage of adverse events. The small sample size and imbalanced distribution of the type of vaccines received limits the external generalizability of our results.

STUDY REGISTRATION

The cohort study was registered at the Philippine Health Research Registry on December 14, 2020 (PHRR201214-003199).

Clinical characteristics and factors for serious outcomes among outpatients infected with the Omicron subvariant BF.7

To evaluate clinical characteristics and identify risk factors associated with severe outcomes in outpatients infected with the Omicron subvariant BF.7, data were collected from outpatients diagnosed with Corona Virus Disease 2019 from December 19, 2022 to January 5, 2023. Clinical characteristics were analyzed using descriptive statistics. Univariate and multivariate logistic regression analyses were conducted to identify factors associated with serious outcomes. Variables with a p < 0.10 in the univariate analysis were included in the multivariate model. Our study analyzed 770 patients, of whom 380 (49.4%) were male, with a median age of 59. The most common symptoms reported were cough (71.2%), fever (64.7%), and sore throat (37.7%). Fever lasted an average of 5.93 ± 3.37 days for the general population and 10.64 ± 7.12 days for impaired-immunity patients. Most cases were mild (68.7%), followed by moderate (27.1%). Severe cases accounted for 2.2%, with 0.5% critically ill. Serious outcomes occurred in 4.2% of cases, with 11 deaths during follow-up. Underlying-diseases patients had a higher rate of serious outcomes. Factors associated with serious outcomes included receiving a three-dose vaccination (odds ratio [OR] = 0.324, 95% confidence interval [CI]: 0.113-0.932, p = 0.037), male gender (OR = 2.890, 95% CI: 1.107-7.548, p = 0.030), age (OR = 1.060, 95% CI: 1.024-1.097, p = 0.001), and chest tightness or dyspnea at the time of visit (OR = 4.861, 95% CI: 2.054-11.507, p < 0.001). Our study found that cough, fever, and sore throat were the most common symptoms reported by patients. Receiving a three-dose vaccination was protective, while male gender, age, and chest tightness or dyspnea were identified as risk factors for serious outcomes.

The prevalence of and factors related to reinfection with COVID-19 in Ahvaz, Iran: A comparative cross-sectional study

Background and Aims

Reinfection with the coronavirus disease 2019 (COVID-19) virus may be as serious as the first infection, exposing people to risks such as admission to hospital or even death. This study aimed to evaluate the prevalence of and the factors related to reinfection in Ahvaz, Iran.

Methods

This was a comparative cross-sectional study that was conducted on 200 reinfected individuals and 200 people who had once been infected with COVID-19. Infection with COVID-19 was confirmed using the polymerase chain reaction (PCR) test, and those with reinfection had to have a negative PCR test after recovery from the first infection and a positive PCR test for COVID-19 > 90 days after the first infection. Data was collected using a questionnaire and a checklist. Data were analyzed using the Chi-square test, independent t-test, and logistic regression test.

Results

Around 7000 reinfections were observed in this study, and the prevalence of reinfection was 0.59% in Ahvaz City. A large proportion of the participants in the control group, 133 (66.5%) received two doses of COVID-19 vaccines compared with 110 (55%) in the reinfected group (p = 0.003), and 43 (21.5%) of reinfected participants did not receive any vaccine. Older people were 0.982 times more likely to get reinfected with COVID-19 (95% confidence interval [CI]: 0.966-0.997). Also, those receiving vaccination once or twice were 2.311 and 2.498 times less likely to get reinfected with COVID-19, respectively (95% CI: 1.093-4.887 and 1.281-4.872, respectively).

Conclusion

The findings of this study showed that the prevalence of reinfection among people in Ahvaz City was 0.59%. Older individuals, those without vaccination or with suboptimal vaccination, and people with comorbidities were at a higher risk for reinfection. Health policymakers should pay more attention to factors related to reinfection with COVID-19.

The Omicron Variant Reinfection Risk among Individuals with a Previous SARS-CoV-2 Infection within One Year in Shanghai, China: A Cross-Sectional Study

Reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants due to immune escape is challenging for the global response to the pandemic. We estimated the Omicron reinfection prevalence among people who had a previous SARS-CoV-2 infection in Shanghai, China. We conducted a telephone survey in December 2022 with those who had previously been infected with Omicron between March and May 2022. Information on their demographics, coronavirus disease 2019 (COVID-19) testing, and vaccination history was collected. The overall and subgroup reinfection rates were estimated and compared. Among the 1981 respondents who were infected between March and May 2022, 260 had positive nucleic acid or rapid antigen tests in December 2022, with an estimated reinfection rate of 13.1% (95% confidence interval [95% CI]: 11.6-14.6). The reinfection rate for those who had a booster vaccination was 11.4% (95% CI: 9.2-13.7), which was significantly lower than that for those with an incomplete vaccination series (15.2%, 95% CI: 12.3-18.1) (adjusted odds ratio [aOR]: 0.579; 95% CI: 0.412-0.813). Reinfection with the Omicron variant was lower among individuals with a previous SARS-CoV-2 infection and those who had a booster vaccination, suggesting that hybrid immunity may offer protection against reinfection with Omicron sublineages.

The Impact of Vaccination on COVID-19 Burden of Disease in the Adult and Elderly Population: A Systematic Review of Italian Evidence

COVID-19 is a major global health threat, with millions of confirmed cases and deaths worldwide. Containment and mitigation strategies, including vaccination, have been implemented to reduce transmission and protect the population. We conducted two systematic reviews to collect nonrandomized studies investigating the effects of vaccination on COVID-19-related complications and deaths in the Italian population. We considered studies conducted in Italian settings and written in English that contained data on the effects of vaccination on COVID-19-related mortality and complications. We excluded studies that pertained to the pediatric population. In total, we included 10 unique studies in our two systematic reviews. The results showed that fully vaccinated individuals had a lower risk of death, severe symptoms, and hospitalization compared to unvaccinated individuals. The review also looked at the impact of vaccination on post-COVID-19 syndrome, the effectiveness of booster doses in older individuals, and nationwide adverse events. Our work highlights the crucial role that vaccination campaigns have played in reducing the burden of COVID-19 disease in the Italian adult population, positively impacting the pandemic trajectory in Italy.

Elder and booster vaccination associates with decreased risk of serious clinical outcomes in comparison of Omicron and Delta variant: A meta-analysis of SARS-CoV-2 infection

Background

The COVID-19 pandemic brings great pressure to the public health systems. This meta-analysis aimed to compare the clinical outcomes among different virus variants, to clarify their impact on medical resources and to provide evidence for the formulation of epidemic prevention policies.

Methods

A systematic literature search was performed in the PubMed, Embase, and Cochrane Library databases using the key words "Omicron" and "Delta." The adjusted Risk ratios (RRs), Odds ratios (ORs) and Hazard ratios (HRs) were extracted, and RRs and Rate difference % (RD%) were used to interpret the risk estimates of the outcomes ultimately.

Results

Forty-three studies were included, with 3,812,681 and 14,926,841 individuals infected with SARS-CoV-2 Delta and Omicron variant, respectively. The relative risks of hospitalization, death, ICU admission, and mechanical ventilation use after infection with the Omicron variant were all significantly reduced compared those after infection with the Delta variant (RRhospitalization = 0.45, 95%CI: 0.40-0.52; RRdeath = 0.37, 95%CI: 0.30-0.45; RRICU = 0.35, 95%CI: 0.29-0.42; RRmechanical ventilation = 0.33, 95%CI: 0.25-0.44). The change of both absolute and relative risks for hospitalization was more evident (RR = 0.47, 95%CI: 0.42-0.53；RD% =10.61, 95%CI: 8.64-12.59) and a significant increase was observed for the absolute differences in death in the elderly (RD% = 5.60, 95CI%: 4.65-6.55); the change of the absolute differences in the risk of hospitalization and death were most markedly observed in the patients with booster vaccination (RD%hospitalization = 8.60, 95CI%: 5.95-11.24; RD%death = 3.70, 95CI%: 0.34-7.06).

Conclusion

The ability of the Omicron variant to cause severe clinical events has decreased significantly, as compared with the Delta variant, but vulnerable populations still need to be vigilant. There was no interaction between the vaccination doses and different variants.

Attitudes of University Students towards Mandatory COVID-19 Vaccination Policies: A Cross-Sectional Survey in Rome, Italy

Mandatory vaccination (MV) against COVID-19 is a contentious topic. In this study, we used logistic regression models to identify attitudes among Sapienza University students towards MV for COVID-19. We considered three different scenarios: mandatory COVID-19 vaccination (MCV) for healthcare workers (HCWs) (Model 1), for all people aged ≥ 12 years (Model 2), and for admission to schools and universities (Model 3). We collected 5287 questionnaires over a six-month period and divided these into three groups (September-October 2021, November-December 2021, and January-February 2022). MCV for HCWs was the most strongly supported policy (69.8% in favour), followed by MCV for admission to schools and universities (58.3%), and MCV for the general population (54.6%). In a multivariable analysis, the models showed both similarities and differences. There was no association of socio-demographic characteristics with the outcomes, apart from being enrolled in non-healthcare courses, which negatively affected Models 2 and 3. A greater COVID-19 risk perception was generally associated with a more positive attitude towards MCV, although heterogeneously across models. Vaccination status was a predictor of being in favour of MCV for HCWs, whereas being surveyed in November-February 2022 favoured MCV for admission to schools and universities. Attitudes towards MCV were variable across policies; thus, to avoid unintended consequences, these aspects should be carefully considered by policymakers.

Mucosal immune response after the booster dose of the BNT162b2 COVID-19 vaccine

BACKGROUND

To date, only a few studies reported data regarding the development of mucosal immune response after the BNT162b2-booster vaccination.

METHODS

Samples of both serum and saliva of 50 healthcare workers were collected at the day of the booster dose (T3) and after two weeks (T4). Anti-S1-protein IgG and IgA antibody titres and the neutralizing antibodies against the Wuhan wild-type Receptor-Binding Domain in both serum and saliva were measured by quantitative and competitive ELISA, respectively. Data were compared with those recorded after the primary vaccination cycle (T2). Neutralizing antibodies against the variants of concern were measured in those individuals with anti-Wuhan neutralizing antibodies in their saliva.

FINDINGS

After eight months from the second dose, IgG decreased in both serum (T2_GMC: 23,838.5 ng/ml; T3_GMC: 1473.8 ng/ml) and saliva (T2_GMC: 12.9 ng/ml; T3_GMC: 0.3 ng/ml). Consistently, serum IgA decreased (T2_GMC: 48.6 ng/ml; T3_GMC: 6.4 ng/ml); however, salivary IgA showed a different behaviour and increased (T2_GMC: 0.06 ng/ml; T3_GMC: 0.41 ng/ml), indicating a delayed activation of mucosal immunity. The booster elicited higher titres of both IgG and IgA when compared with the primary cycle, in both serum (IgG T4_GMC: 98,493.9 ng/ml; IgA T4_GMC: 187.5 ng/ml) and saliva (IgG T4_GMC: 21.9 ng/ml; IgA T4_GMC: 0.65 ng/ml). Moreover, the booster re-established the neutralizing activity in the serum of all individuals, not only against the Wuhan wild-type antigen (N = 50; INH: 91.6%) but also against the variants (Delta INH: 91.3%; Delta Plus INH: 89.8%; Omicron BA.1 INH: 85.1%). By contrast, the salivary neutralizing activity was high against the Wuhan antigen in 72% of individuals (N = 36, INH: 62.2%), but decreased against the variants, especially against the Omicron BA.1 variant (Delta N = 27, INH: 43.1%; Delta Plus N = 24, INH: 35.2%; Omicron BA.1 N = 4; INH: 4.7%). This was suggestive for a different behaviour of systemic immunity observed in serum with respect to mucosal immunity described in saliva (Wald chi-square test, 3 df of interaction between variants and sample type = 308.2, p < 0.0001).

INTERPRETATION

The BNT162b2-booster vaccination elicits a strong systemic immune response but fails in activating an effective mucosal immunity against the Omicron BA.1 variant.

FUNDING

This work was funded by the Department of Medicine and Surgery, University of Insubria, and supported by Fondazione Umberto Veronesi (COVID-19 Insieme per la ricerca di tutti, 2020), Italy.

Older age and depressive state are risk factors for re-positivity with SARS-CoV-2 Omicron variant

Background

The reinfection rate of SARS-CoV-2 Omicron variant is high; thus, exploring the risk factors for reinfection is important for the effective control of the epidemic. This study aimed to explore the effects of psychological and sleep factors on re-positivity with Omicron.

Methods

Through a prospective cohort study, 933 adult patients diagnosed with Omicron BA.2.2 infection and testing negative after treatment were included for screening and follow-up. We collected data on patients' demographic characteristics, SARS-CoV-2 Omicron vaccination status, anxiety, depression, and sleep status. Patients underwent nucleic acid testing for SARS-CoV-2 Omicron for 30 days. Regression and Kaplan-Meier analyses were used to determine the risk factors for re-positivity of Omicron.

Results

Ultimately, 683 patients were included in the analysis. Logistic regression analysis showed that older age (P = 0.006) and depressive status (P = 0.006) were two independent risk factors for Omicron re-positivity. The odds ratios of re-positivity in patients aged ≥60 years and with a Patient Health Questionnaire-9 (PHQ-9) score ≥5 was 1.82 (95% confidence interval:1.18-2.78) and 2.22 (1.27-3.85), respectively. In addition, the time from infection to recovery was significantly longer in patients aged ≥60 years (17.2 ± 4.5 vs. 16.0 ± 4.4, P = 0.003) and in patients with PHQ-9≥5 (17.5 ± 4.2vs. 16.2 ± 4.5, P = 0.026). Kaplan-Meier analysis showed that there was a significantly higher primary re-positivity rate in patients aged ≥60 years (P = 0.004) and PHQ-9 ≥ 5 (P = 0.007).

Conclusion

This study demonstrated that age of ≥60 years and depressive status were two independent risk factors for re-positivity with Omicron and that these factors could prolong the time from infection to recovery. Thus, it is necessary to pay particular attention to older adults and patients in a depressive state.