Trends and Correlates of Breakthrough Infections With SARS-CoV-2

Single-Cell RNA Sequencing of Baseline Immune Profiles After Third Vaccination Associated with Subsequent SARS-CoV-2 Infection in Naïve Individuals

Even though vaccines protected many from infection, not all were protected, and vaccinated individuals displayed a wide range of clinical outcomes, from complete protection against infection to multiple breakthrough infections. This study aimed to identify baseline differences following identical ChAdOx1/ChAdOx1/BNT162b2 in infection-free and breakthrough-infected individuals to find molecular signatures linked to enhanced SARS-CoV-2 protection. Samples from a previous longitudinal study were analyzed, classifying subjects as 'Protected' or 'Infected' based on infection status over two years. SARS-CoV-2-specific immunological assays and single-cell RNA sequencing evaluated baseline differences. Although humoral response measurements showed no significant difference, enhanced cellular responses via enzyme-linked immunospot assays were observed in the Protected group. Differentially expressed genes and pathway analysis of T/NK subsets showed the Infected group had reduced inflammation and interferon responses. The Infected group also displayed downregulated interaction with CD4+ T cells. B subset analysis revealed more memory B cells in the Infected group, accompanied by downregulation of immune regulatory genes and upregulation of the small ubiquitin-related modifier pathway. Our findings revealed differential molecular signatures in the baseline immune subsets of vaccinated individuals with prolonged protection and breakthrough infection. Reduced immune regulation and altered cell interactions may contribute to breakthrough infection, providing insights for future vaccine development and targeted protective strategies.

COVID-19 vaccine updates for people under different conditions

SARS-CoV-2 has caused global waves of infection since December 2019 and continues to persist today. The emergence of SARS-CoV-2 variants with strong immune evasion capabilities has compromised the effectiveness of existing vaccines against breakthrough infections. Therefore, it is important to determine the best utilization strategies for different demographic groups given the variety of vaccine options available. In this review, we will discuss the protective efficacy of vaccines during different stages of the epidemic and emphasize the importance of timely updates to target prevalent variants, which can significantly improve immune protection. While it is recognized that vaccine effectiveness may be lower in certain populations such as the elderly, individuals with chronic comorbidities (e.g., diabetes with poor blood glucose control, those on maintenance dialysis), or those who are immunocompromised compared to the general population, administering multiple doses can result in a strong protective immune response that outweighs potential risks. However, caution should be exercised when considering vaccines that might trigger an intense immune response in populations prone to inflammatory flare or other complications. In conclusion, individuals with special conditions require enhanced and more effective immunization strategies to prevent infection or reinfection, as well as to avoid the potential development of long COVID.

Methodology of comparative studies on the relative effectiveness of COVID-19 vaccines: a systematic review

BACKGROUND

This study aimed to comprehensively outline the methodological approaches used in published research comparing the vaccine effectiveness (VE) of coronavirus disease 2019 (COVID-19) vaccines.

METHODS

A systematic search was conducted on June 13, 2024, to identify comparative studies evaluating the effectiveness of mRNA versus non-mRNA and monovalent versus bivalent COVID-19 vaccines. We screened titles, abstracts, and full texts, collecting data on publication year, country, sample size, study population composition, study design, VE estimates, outcomes, and covariates. Studies that reported relative VE (rVE) were analyzed separately from those that did not.

RESULTS

We identified 25 articles comparing rVE between mRNA and non-mRNA COVID-19 vaccines, as well as between monovalent and bivalent formulations. Among the studies assessing VE by vaccine type, 126 did not provide rVE estimates. Comparative VE studies frequently employed retrospective cohort designs. Among the definitions of rVE used, the most common were hazard ratio and absolute VE, calculated as (1-odds ratio)×100. Studies were most frequently conducted in the United Kingdom and the United States, and the most common outcome was infection. Most targeted the general population and assessed the VE of mRNA vaccines using the AstraZeneca vaccine as a reference. A small proportion, 7.3% (n=11), did not adjust for any variables. Only 3 studies (2.0%) adjusted for all core confounding variables recommended by the World Health Organization.

CONCLUSION

Few comparative studies of COVID-19 vaccines have incorporated rVE methodologies. Reporting rVE and employing a consistent set of covariates can broaden our understanding of COVID-19 vaccines.

COVID-19 Vaccine Effectiveness of Booster Doses Against Delta and Omicron Variants Over Follow-up Times Using Longitudinal Meta-analysis

BACKGROUND

COVID-19 is a viral disease caused by the SARS-CoV-2, leading to several variants. This study aimed to examine the effectiveness of booster doses against the Delta and Omicron variants over different follow-up times. Study Design: This was a longitudinal meta-analysis.

METHODS

Searches were performed in PubMed, Cochrane Library, Scopus, and Web of Science databases, and eighty studies were selected for investigation. The analyses were separately performed on the unvaccinated control group (UNVCG) and the complete two doses of the vaccine control group (C2DCG) against Delta and Omicron variants. Three outcomes were examined, including symptomatic infection, hospitalization, and death.

RESULTS

Vaccine effectiveness (VE) in UNVCG studies for symptomatic infection revealed a non-linear trend against Omicron with a peak of 67.3%, declining to 27.1% after 25 weeks after a booster dose. The mean of VE for hospitalization over time started to decrease after four weeks against Omicron and after eight weeks against Delta. The VE reached a peak at week eight (96.0%) and started to decline with a VE of 93.3% after 20 weeks after the booster dose against Delta. It was 90.8% at week four and decreased to 73.4% after 25 weeks after the booster dose against Omicron. VE in the C2DCG studies demonstrated more decreases in outcomes over time.

CONCLUSION

Our findings showed a tendency to decrease effectiveness over time based on outcomes and variants. The early protection levels were lower in Omicron. Moreover, the VE decrease over time was stronger in Omicron compared to the Delta variant.

Association between humoral serological markers levels and risk of SARS-CoV-2 infection after the primary COVID-19 vaccine course among ANRS0001S COV-POPART cohort participants

BACKGROUND

We assessed the prognostic value of serological humoral markers measured one month after the last dose of the primary COVID-19 vaccine course for predicting the risk of severe acute respiratory syndrome coronavirus 2 SARS-CoV-2 infection over the following six months in specific populations.

METHODS

ANRS0001SCOV-POPART is a French nationwide multicenter prospective observational cohort study assessing the immune response to Covid-19 vaccines routinely administered to 11 subgroups of patients with chronic disease and a control group. Participants from the ANRS0001S COV-POPART were included if they received at least two doses of Covid-19 vaccine for the primary vaccine course, had measurements of anti-Spike, anti-receptor binding domain (RBD) IgG-specific or neutralizing antibodies one month after the end of the primary vaccine course, without being infected by SARS-CoV-2 before the measurement. SARS-CoV-2 infections defined by a positive PCR/antigenic test or seroconversion to detectable anti nucleocapsid antibodies were evaluated until the first COVID-19 booster injection. Cox proportional hazards models taking into account interval-censored data were implemented to estimate the association between each antibody level and the risk of SARS-CoV-2 infection. Predictive performances were evaluated by the area under the receiving operating characteristic curve (AUROC).

RESULTS

Two thousand five hundred seventy adults from a specific population and 1,123 from the control group were included. The cumulative probabilities of SARS-CoV-2 infections at five months after serological measurement were 6.0% 95% confidence interval: [5.0; 7.9] and 10.1% 95% confidence interval: [8.3; 11.9], respectively. Higher levels of anti-Spike IgG antibody were associated with a lower risk of SARS-CoV-2 infections in the control group, but not in the specific populations. Among the specific populations, AUROC were 74.5%, 74.9%, and 72.4% for anti-Spike IgG, anti-RBD IgG, and neutralizing antibodies, respectively. AUROC were superior in the specific populations, 82.0%, 81.2%, and 81.4% for anti-Spike IgG, anti-RBD IgG, and neutralizing antibodies, respectively.

CONCLUSIONS

Vaccine-induced antibody response after the primary course of Covid-19 infection only moderately discriminated between participants developing a SARS-CoV-2 infection during the Omicron wave.

TRIAL REGISTRATION

NCT04824651 (first posted: 2021-04-01).

Breakthrough SARS-CoV-2 infection and disease flares in patients with rheumatoid arthritis: result from COVAD e-survey study

COVID-19 has been suggested as a possible trigger of disease flares in patients with rheumatoid arthritis (RA). However, factors associated with disease flares remain unknown. This study aimed to identify factors associated with breakthrough infection (BIs) and disease flares in patients with RA following COVID-19. We analysed data from RA patients who participated in the COVID-19 vaccination in autoimmune diseases (COVAD) study. Demographic data, patient-reported outcomes, comorbidities, pharmacologic treatment and details regarding disease flares were extracted from the COVAD database. Factors associated with disease flare-ups were determined by multivariate logistic regression analysis. The analysis comprised 1928 patients with RA who participated in the COVAD study. Younger age, Caucasian ethnicity, comorbidities with obstructive chronic pulmonary disease and asthma were associated with COVID-19 breakthrough infection. Moreover, younger age (odds ratio (OR): 0.98, 95% CI 0.96-0.99, p < 0.001), ethnicity other than Asian, past history of tuberculosis (OR: 3.80, 95% CI 1.12-12.94, p = 0.033), treatment with methotrexate (OR: 2.55, 95% CI: 1.56-4.17, p < 0.001), poor global physical health (OR: 1.07, 95% CI 1.00-1.15, p = 0.044) and mental health (OR: 0.91, 95% CI 0.87-0.95, p < 0.001) were independent factors associated disease flares in patients with RA. Our study highlights the impact of socio-demographic factors, clinical characteristics and mental health on disease flares in patients with RA. These insights may help determine relevant strategies to proactively manage RA patients at risk of flares.

SARS-CoV-2 vaccine breakthrough infection in the older adults: a meta-analysis and systematic review

BACKGROUND

Corona Virus Disease 2019 (COVID-19) mRNA vaccine effectiveness (VE) has recently declined, and reports about COVID-19 breakthrough infection have increased. We aimed to conduct a meta-analysis on population-based studies of the prevalence and incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) breakthrough infection amongst older adults worldwide.

METHODS

Studies from PubMed, Embase, Cochrane Library, and Web of Science were systematically screened to determine the prevalence and incidence of SARS-CoV-2 breakthrough infection in older adults from inception to November 2, 2022. Our meta-analysis included 30 studies, all published in English. Pooled estimates were calculated using a random-effect model through the inverse variance method. Publication bias was tested through funnel plots and Egger's regression test, and sensitivity analyses were performed to confirm the robustness of the results. This research was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Thirty publications were included in this meta-analysis (17 on prevalence, 17 on incidence, and 4 on both). The pooled prevalence of COVID-19 breakthrough infection among older adults was 7.7 per 1,000 persons (95% confidence interval [95%CI] 4.0-15.0). At the same time, the pooled incidence was 29.1 per 1000 person-years (95%CI 15.2-55.7).

CONCLUSIONS

This meta-analysis provides estimates of prevalence and incidence in older adults. We concluded that the prevalence and incidence of SARS-CoV-19 breakthrough infection in older people was low. The prevalence and incidence of breakthrough infection admitted to hospital, severe-critical, and deathly was significantly lower. Otherwise, there was considerable heterogeneity among estimates in this study, which should be considered when interpreting the results.

Humoral and cellular immune correlates of protection against COVID-19 in kidney transplant recipients

As solid organ transplant recipients are at high risk of severe COVID-19 and respond poorly to primary SARS-CoV-2 mRNA vaccination, they have been prioritized for booster vaccination. However, an immunological correlate of protection has not been identified in this vulnerable population. We conducted a prospective monocentric cohort study of 65 kidney transplant recipients who received 3 doses of BNT162b2 mRNA vaccine. Associations among breakthrough infection (BTI), vaccine responses, and patient characteristics were explored in 54 patients. Symptomatic COVID-19 was diagnosed in 32% of kidney transplant recipients during a period of 6 months after booster vaccination. During this period, SARS-CoV-2 delta and omicron were the dominant variants in the general population. Univariate Analyses identified the avidity of SARS-CoV-2 receptor binding domain binding IgG, neutralizing antibodies, and SARS-CoV-2 S2-specific interferon gamma responses as correlates of protection against BTI. No demographic or clinical parameter correlated with the risk of BTI. In multivariate analysis, the risk of BTI was best predicted by neutralizing antibody and S2-specific interferon gamma responses. In conclusion, T cell responses may help compensate for the suboptimal antibody response to booster vaccination in kidney transplant recipients. Further studies are needed to confirm these findings.