Effectiveness of Covid-19 Vaccines in Ambulatory and Inpatient Care Settings

COVID-19 vaccination effectiveness rates by week and sources of bias: a retrospective cohort study

OBJECTIVE

To examine COVID-19 vaccine effectiveness over six 7-day intervals after the first dose and assess underlying bias in observational data.

DESIGN AND SETTING

Retrospective cohort study using Columbia University Irving Medical Center data linked to state and city immunisation registries.

OUTCOMES AND MEASURES

We used large-scale propensity score matching with up to 54 987 covariates, fitted Cox proportional hazards models and constructed Kaplan-Meier plots for two main outcomes (COVID-19 infection and COVID-19-associated hospitalisation). We conducted manual chart review of cases in week 1 in both groups along with a set of secondary analyses for other index date, outcome and population choices.

RESULTS

The study included 179 666 patients. We observed increasing effectiveness after the first dose of mRNA vaccines with week 6 effectiveness approximating 84% (95% CI 72% to 91%) for COVID-19 infection and 86% (95% CI 69% to 95%) for COVID-19-associated hospitalisation. When analysing unexpectedly high effectiveness in week 1, chart review revealed that vaccinated patients are less likely to seek care after vaccination and are more likely to be diagnosed with COVID-19 during the encounters for other conditions. Secondary analyses highlighted potential outcome misclassification for International Classification of Diseases, Tenth Revision, Clinical Modification diagnosis, the influence of excluding patients with prior COVID-19 infection and anchoring in the unexposed group. Long-term vaccine effectiveness in fully vaccinated patients matched the results of the randomised trials.

CONCLUSIONS

For vaccine effectiveness studies, observational data need to be scrutinised to ensure compared groups exhibit similar health-seeking behaviour and are equally likely to be captured in the data. While we found that studies may be capable of accurately estimating long-term effectiveness despite bias in early weeks, the early week results should be reported in every study so that we may gain a better understanding of the biases. Given the difference in temporal trends of vaccine exposure and patients' baseline characteristics, indirect comparison of vaccines may produce biased results.

Real-world study of the effectiveness of BBIBP-CorV (Sinopharm) COVID-19 vaccine in the Kingdom of Morocco

Background

The Kingdom of Morocco approved BBIBP-CorV (Sinopharm) COVID-19 vaccine for emergency use on 22 January 2021 in a two-dose, three-to-four-week interval schedule. We conducted a retrospective cohort study to determine real-world BBIBP-CorV vaccine effectiveness (VE) against serious or critical hospitalization of individuals RT-PCR-positive for SARS-CoV-2 during the first five months of BBIBP-CorV use in Morocco.

Methods

The study was conducted among adults 18–99 years old who were tested by RT-PCR for SARS-CoV-2 infection between 1 February and 30 June 2021. RT-PCR results were individually linked with outcomes from the COVID-19 severe or critical hospitalization dataset and with vaccination histories from the national vaccination registration system. Individuals with partial vaccination (< 2 weeks after dose two) or in receipt of any other COVID-19 vaccine were excluded. Unadjusted and adjusted VE estimates against hospitalization for serious or critical illness were made by comparing two-dose vaccinated and unvaccinated individuals in logistic regression models, calculated as (1-odds ratio) * 100%.

Results

There were 348,190 individuals able to be matched across the three databases. Among these, 140,892 were fully vaccinated, 206,149 were unvaccinated, and 1,149 received homologous BBIBP-CorV booster doses. Unadjusted, full-series, unboosted BBIBP-CorV VE against hospitalization for serious or critical illness was 90.2% (95%CI: 87.8—92.0%). Full-series, unboosted VE, adjusted for age, sex, and calendar day of RT-PCR test, was 88.5% (95%CI: 85.8—90.7%). Calendar day- and sex-adjusted VE was 96.4% (95%CI: 94.6—97.6%) for individuals < 60 years, and was 53.3% (95%CI: 39.6—63.9%) for individuals 60 years and older. There were no serious or critical illnesses among BBIBP-CorV-boosted individuals.

Conclusions

Effectiveness of Sinopharm’s BBIBP-CorV was consistent with phase III clinical trial results. Two doses of BBIBP-CorV was highly protective against COVID-19-associated serious or critical hospitalization in working-age adults under real-world conditions and moderately effective in older adults. Booster dose vaccination was associated with complete protection, regardless of age, although only a small proportion of subjects received booster doses.

Effectiveness of BNT162b2 and CoronaVac vaccinations against mortality and severe complications after SARS-CoV-2 Omicron BA.2 infection: a case-control study

Data regarding protection against mortality and severe complications after Omicron BA.2 infection with CoronaVac and BNT162b2 vaccines remains limited. We conducted a case–control study to evaluate the risk of severe complications and mortality following 1–3 doses of CoronaVac and BNT162b2 using electronic health records database. Cases were adults with their first COVID-19-related mortality or severe complications between 1 January and 31 March 2022, matched with up-to 10 controls by age, sex, index date, and Charlson Comorbidity Index. Vaccine effectiveness against COVID-19-related mortality and severe complications by type and number of doses was estimated using conditional logistic regression adjusted for comorbidities and medications. Vaccine effectiveness (95% CI) against COVID-19-related mortality after two doses of BNT162b2 and CoronaVac were 90.7% (88.6–92.3) and 74.8% (72.5–76.9) in those aged ≥65, 87.6% (81.4–91.8) and 80.7% (72.8–86.3) in those aged 50–64, 86.6% (71.0–93.8) and 82.7% (56.5–93.1) in those aged 18–50. Vaccine effectiveness against severe complications after two doses of BNT162b2 and CoronaVac were 82.1% (74.6–87.3) and 58.9% (50.3–66.1) in those aged ≥65, 83.0% (69.6–90.5) and 67.1% (47.1–79.6) in those aged 50–64, 78.3% (60.8–88.0) and 77.8% (49.6–90.2) in those aged 18–50. Further risk reduction with the third dose was observed especially in those aged ≥65 years, with vaccine effectiveness of 98.0% (96.5–98.9) for BNT162b2 and 95.5% (93.7–96.8) for CoronaVac against mortality, 90.8% (83.4–94.9) and 88.0% (80.8–92.5) against severe complications. Both CoronaVac and BNT162b2 vaccination were effective against COVID-19-related mortality and severe complications amidst the Omicron BA.2 pandemic, and risks decreased further with the third dose.

Multiplex protein profiling of bronchial aspirates reveals disease-, mortality- and respiratory sequelae-associated signatures in critically ill patients with ARDS secondary to SARS-CoV-2 infection

Introduction

Bronchial aspirates (BAS) obtained during invasive mechanical ventilation (IMV) constitutes a useful tool for molecular phenotyping and decision making.

Aim

To identify the proteomic determinants associated with disease pathogenesis, all-cause mortality and respiratory sequelae in BAS samples from critically ill patients with SARS-CoV-2-induced ARDS.

Methods

Multicenter study including 74 critically ill patients with COVID-19 and non-COVID-19 ARDS. BAS were obtained by bronchoaspiration after IMV initiation. Three hundred sixty-four proteins were quantified using proximity extension assay (PEA) technology. Random forest models were used to assess predictor importance.

Results

After adjusting for confounding factors, CST5, NADK, SRPK2 and TGF-α were differentially detected in COVID-19 and non-COVID-19 patients. In random forest models for COVID-19, CST5, DPP7, NADK, KYAT1 and TYMP showed the highest variable importance. In COVID-19 patients, reduced levels of ENTPD2 and PTN were observed in nonsurvivors of ICU stay, even after adjustment. AGR2, NQO2, IL-1α, OSM and TRAIL showed the strongest associations with in-ICU mortality and were used to construct a protein-based prediction model. Kaplan-Meier curves revealed a clear separation in mortality risk between subgroups of PTN, ENTPD2 and the prediction model. Cox regression models supported these findings. In survivors, the levels of FCRL1, NTF4 and THOP1 in BAS samples obtained during the ICU stay correlated with lung function (i.e., D_LCO levels) 3 months after hospital discharge. Similarly, Flt3L and THOP1 levels were correlated with radiological features (i.e., TSS). These proteins are expressed in immune and nonimmune lung cells. Poor host response to viral infectivity and an inappropriate reparative mechanism seem to be linked with the pathogenesis of the disease and fatal outcomes, respectively.

Conclusion

BAS proteomics identified novel factors associated with the pathology of SARS-CoV-2-induced ARDS and its adverse outcomes. BAS-based protein testing emerges as a novel tool for risk assessment in the ICU.

COVID-19 Disease and Vaccination: Knowledge, Fears, Perceptions and Feelings of Regret for Not Having Been Vaccinated among Hospitalized Greek Patients Suffering SARS-CoV-2 Infection

Background: The development of vaccines against COVID-19 has greatly altered the natural course of this infection, reducing the disease’s severity and patients’ hospitalization. However, hesitancy against vaccination remains an obstacle in the attempt to achieve appropriate herd immunity that could reduce the spread of SARS-CoV-2. The aim of this study was to investigate the perceptions and attitudes of COVID-19 patients hospitalized during the fourth pandemic wave in two Greek hospitals and assess whether their experience had changed their intentions regarding vaccination against COVID-19. Methods: This is a cross-sectional, questionnaire-based survey, conducted from 31 August 2021 to 18 February 2022 in the COVID-19 departments of two tertiary care hospitals. The questionnaire included questions regarding the patients’ educational level, knowledge and beliefs regarding SARS-CoV-2, personal protection measures, beliefs regarding vaccination, vaccination status, reasons for not been vaccinated against SARS-CoV-2, feelings of regret for not been vaccinated, and willingness to be vaccinated in the future. All adult patients with COVID-19 were eligible, regardless of their vaccination status against SARS-CoV-2. Results: In total, 162 patients agreed and participated in the study, with 97% of them suffering severe COVID-19. Their median age was 56 years, and 59.9% (97 patients) were male. Among them, 43.8% had been vaccinated against COVID-19. When unvaccinated patients were asked the reasons for not being vaccinated, the most frequent responses were that they were waiting for more scientific data, due to uncertainty about long-term consequences of the vaccine, and their fear of thrombosis. When at discharge, unvaccinated hospitalized COVID-19 patients were asked whether they would get vaccinated if they could turn time back, and 64.7% of them replied positively. Conclusions: The study reveals several patients’ fears and misconceptions and suggests that there is room for implementing measures that could reduce knowledge gaps allowing for improvement of vaccination rates against COVID-19.

Immunogenicity, effectiveness, safety and psychological impact of COVID-19 mRNA vaccines

In December 2019, a new single-stranded RNA coronavirus, SARS-CoV-2, appeared in China and quickly spread around the world leading to a pandemic. Infection with SARS-CoV-2 generates symptoms ranging from asymptomatic to severe, occasionally requiring hospitalization in intensive care units, and, in more severe cases, leading to death. Scientists and researchers around the world have made a real race against time to develop various vaccines to slow down and stop the spread of the virus. In addition to conventional viral vector vaccines, new generation mRNA vaccines, BNT152b2 (Comirnaty) and mRNA-1273 (Spikevax), have been developed respectively by Pfizer/BioNTech and Moderna. These vaccines act on immune cells to induce an immune response with the production of specific antibodies against Spike protein of SARS-CoV-2, and to stimulate the differentiation of T and B memory cells. The objective of this review is to provide a detailed picture of the validity of these new vaccines and the safety of vaccination. Not only was the immunogenic effect of mRNA vaccines evaluated, but also the psychosocial impact they had on the population. The data collected show that this type of vaccine can also be an excellent candidate for future treatment and eradication of possible new pathologies with viral and non-viral etiology.

Lower vaccine-acquired immunity in the elderly population following two-dose BNT162b2 vaccination is alleviated by a third vaccine dose

Understanding the impact of age on vaccinations is essential for the design and delivery of vaccines against SARS-CoV-2. Here, we present findings from a comprehensive analysis of multiple compartments of the memory immune response in 312 individuals vaccinated with the BNT162b2 SARS-CoV-2 mRNA vaccine. Two vaccine doses induce high antibody and T cell responses in most individuals. However, antibody recognition of the Spike protein of the Delta and Omicron variants is less efficient than that of the ancestral Wuhan strain. Age-stratified analyses identify a group of low antibody responders where individuals ≥60 years are overrepresented. Waning of the antibody and cellular responses is observed in 30% of the vaccinees after 6 months. However, age does not influence the waning of these responses. Taken together, while individuals ≥60 years old take longer to acquire vaccine-induced immunity, they develop more sustained acquired immunity at 6 months post-vaccination. A third dose strongly boosts the low antibody responses in the older individuals against the ancestral Wuhan strain, Delta and Omicron variants.

Responses to SARS-CoV-2 vaccines in different populations are important to define efficacy. Here the authors show using a cohort in Singapore that two doses of mRNA vaccine is less effective in recipients over 60 years of age and that a further dose of vaccine can improve these antibody levels.

Characteristics associated with the residual risk of severe COVID-19 after a complete vaccination schedule: A cohort study of 28 million people in France

Background

Methods

Findings

Interpretation

Funding

Adults hospitalized with breakthrough COVID-19 have lower mortality than matched unvaccinated adults

BACKGROUND

Coronavirus disease 2019 (COVID-19) breakthrough infections are common.

OBJECTIVE

Evaluate in-hospital mortality of patients with COVID-19 by vaccination status using retrospective cohort study.

METHODS

We generated propensity scores for receipt of full vaccination in adults requiring supplemental oxygen hospitalized at Kaiser Permanente Northern California (1 April 2021 to 30 November 2021) with positive severe acute respiratory syndrome coronavirus 2 polymerase chain reaction tests. Optimal matching of fully vaccinated/unvaccinated patients was performed comparing in-hospital mortality.

RESULTS

Of 7305 patients, 1463 (20.0%) were full, 138 (1.9%) were partial, and 5704 (78.1%) were unvaccinated. Fully vaccinated were older than partial or unvaccinated (71.0, 63.0, and 54.0 years, respectively, p < 0.001) with more comorbidities (Comorbidity Point Scores 33.0, 22.0, and 10.0, p < 0.001) and immunosuppressant (11.5%, 8.7%, and 3.0%, p < 0.001) or chemotherapy exposure (2.8%, 0.7%, and 0.4%, p < 0.001). Fewer fully vaccinated patients died compared to matched unvaccinated (9.0% vs. 16.3%, p < 0.0001).

CONCLUSION

Fully vaccinated patients are less likely to die compared to matched unvaccinated patients.

Prevention of SARS-CoV-2 and respiratory viral infections in healthcare settings: current and emerging concepts

PURPOSE OF REVIEW

COVID-19 has catalyzed a wealth of new data on the science of respiratory pathogen transmission and revealed opportunities to enhance infection prevention practices in healthcare settings.

RECENT FINDINGS

New data refute the traditional division between droplet vs airborne transmission and clarify the central role of aerosols in spreading all respiratory viruses, including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), even in the absence of so-called 'aerosol-generating procedures' (AGPs). Indeed, most AGPs generate fewer aerosols than talking, labored breathing, or coughing. Risk factors for transmission include high viral loads, symptoms, proximity, prolonged exposure, lack of masking, and poor ventilation. Testing all patients on admission and thereafter can identify early occult infections and prevent hospital-based clusters. Additional prevention strategies include universal masking, encouraging universal vaccination, preferential use of N95 respirators when community rates are high, improving native ventilation, utilizing portable high-efficiency particulate air filters when ventilation is limited, and minimizing room sharing when possible.

SUMMARY

Multifaceted infection prevention programs that include universal testing, masking, vaccination, and enhanced ventilation can minimize nosocomial SARS-CoV-2 infections in patients and workplace infections in healthcare personnel. Extending these insights to other respiratory viruses may further increase the safety of healthcare and ready hospitals for novel respiratory viruses that may emerge in the future.

Early diagnosis by antigen test kit and early treatment by antiviral therapy: An ambulatory management strategy during COVID-19 crisis in Thailand

This study aimed to assess the clinical characteristics of patients who registered at the Siriraj Favipiravir Clinic and to share our experiences in this comparatively unique clinical setting. This retrospective study included patients who registered at the Siriraj Favipiravir Clinic during August 11, 2021 to September 14, 2021. Included adult patients were those with severe acute respiratory syndrome coronavirus 2 (coronavirus disease 2019 [COVID-19]) infection confirmed by antigen test kit (ATK) or real-time reverse transcription-polymerase chain reaction, no favipiravir contraindication, no prior COVID-19 treatment, and not receiving care from another medical facility. Demographic data and outcomes were collected and analyzed. Of the 1168 patients (mean age: 44.8 ± 16.4 years, 55.7% female) who registered at the clinic, 117 (10%) did not meet the treatment criteria, and 141 (12%) patients did not pick up their medication. One-third of patients had at least 1 symptom that indicated severe disease. Higher proportion of unvaccinated status (56.7% vs 47.5%, P = .005), higher proportion of persons with risk factors for disease progression (37.7% vs 31.3%, P = .028), and longer duration between the date of clinic registration and the date of positive diagnostic test (3 vs 2 days, P = .004) were significantly more commonly observed in the severe disease group compared to the nonsevere disease group. The duration between symptom onset and the date of clinic registration was significantly longer in the real-time reverse transcription-polymerase chain reaction group than in the ATK group (6 vs 4 days, P < .001). Most patients (90.0%) had completed favipiravir treatment regimen. The improvement and mortality rates were 86.7% and 1.2%, respectively. COVID-19 severity is associated with vaccination status, baseline risk factors, and timing between disease detection and treatment. The use of ATK influences patients to seek treatment significantly earlier in ambulatory setting. Our early diagnosis and antiviral treatment strategy yielded favorable results in an outpatient setting during a COVID-19 outbreak in Thailand.

Assessing the Dynamic Outcomes of Containment Strategies against COVID-19 under Different Public Health Governance Structures: A Comparison between Pakistan and Bangladesh

COVID-19 scenarios were run using an epidemiological mathematical model (system dynamics model) and counterfactual analysis to simulate the impacts of different control and containment measures on cumulative infections and deaths in Bangladesh and Pakistan. The simulations were based on national-level data concerning vaccination level, hospital capacity, and other factors, from the World Health Organization, the World Bank, and the Our World in Data web portal. These data were added to cumulative infections and death data from government agencies covering the period from 18 March 2020 to 28 February 2022. Baseline curves for Pakistan and Bangladesh were obtained using piecewise fitting with a consideration of different events against the reported data and allowing for less than 5% random errors in cumulative infections and deaths. The results indicate that Bangladesh could have achieved more reductions in each key outcome measure by shifting its initial lockdown at least five days backward, while Pakistan would have needed to extend its lockdown to achieve comparable improvements. Bangladesh’s second lockdown appears to have been better timed than Pakistan’s. There were potential benefits from starting the third lockdown two weeks earlier for Bangladesh and from combining this with the fourth lockdown or canceling the fourth lockdown altogether. Adding a two-week lockdown at the beginning of the upward slope of the second wave could have led to a more than 40 percent reduction in cumulative infections and a 35 percent reduction in cumulative deaths for both countries. However, Bangladesh’s reductions were more sensitive to the duration of the lockdown. Pakistan’s response was more constrained by medical resources, while Bangladesh’s outcomes were more sensitive to both vaccination timing and capacities. More benefits were lost when combining multiple scenarios for Bangladesh compared to the same combinations in Pakistan. Clearly, cumulative infections and deaths could have been highly impacted by adjusting the control and containment measures in both national settings. However, COVID-19 outcomes were more sensitive to adjustment interventions for the Bangladesh context. Disaggregated analyses, using a wider range of factors, may reveal several sub-national dynamics. Nonetheless, the current research demonstrates the relevance of lockdown timing adjustments and discrete adjustments to several other control and containment measures.

Assessment of unvaccinated and vaccinated patients with coronavirus disease 2019 (COVID-19) treated with monoclonal antibodies during the delta wave (July 1-August 20, 2021): a retrospective observational monocentric study

Background

Monoclonal antibodies (mAb) prevent COVID-19 progression when administered early. We compared mAb treatment outcomes among vaccinated and unvaccinated patients during Delta wave and assessed the feasibility of implementing stricter eligibility criteria in the event of mAb scarcity.

Methods

We conducted a retrospective observational study of casirivimab/imdevimab recipients with mild-to-moderate COVID-19 infection in an emergency department or outpatient infusion center (July 1–August 20, 2021). Primary outcome was all-cause hospital admission within 30 days post-treatment between vaccinated vs. unvaccinated patients during Delta surge in the Bronx, NY.

Results

A total of 250 patients received casirivimab/imdevimab (162 unvaccinated vs. 88 vaccinated). The median age was 39 years for unvaccinated patients, and 52 years for vaccinated patients (p < 0.0001). The median number of EUA criteria met was 1 for unvaccinated and 2 for vaccinated patients (p < 0.0001). Overall, 6% (15/250) of patients were admitted within 30 days post-treatment. Eleven unvaccinated patients (7%) were admitted within 30-days compared to 4 (5%) vaccinated patients (p = 0.48).

Conclusions

All-cause 30-day admission was not statistically different between vaccinated and unvaccinated patients. When federal allocation of therapies is limited, programs must prioritize patients at highest risk of hospitalization and death regardless of vaccination status.

Effectiveness of Comirnaty® Vaccine and Correlates of Immunogenicity and Adverse Reactions: A Single-Center Prospective Case Series Study

The literature suggests that real-world data on the effectiveness and safety of the BNT162b2 vaccine depend on the characteristics of the vaccinated volunteers. The purpose of this study was to evaluate antibody responses and kinetics, established association with sociodemographic and clinical characteristics, and adverse reactions after complete vaccination with the BNT162b2 vaccine. A single-center prospective case series study was conducted with 112 eligible volunteers who were institutionalized elderly and health care workers with had a negative anti-SARS-CoV-2 IgG test prior to receiving the first dose of vaccine. At least one serological antibody test after each dose of vaccine was performed. Volunteers with a positive SARS-CoV-2 PCR test before vaccination were excluded. A chemiluminescent immunoassay anti-S1 antibody assay performed a serological evaluation. Both vaccine doses elicited positive IgG antibodies 3799.0 ± 2503.0 AU/mL and 8212.0 ± 4731.0 AU/mL after 20 days of the first and second doses of BNT162b2, respectively. Comirnaty® vaccine induced an immune response with antibody production against SARS-CoV-2 in 100% of participants, regardless of age (Spearman rho = −0.10, p-value = 0.312), body mass index (Spearman rho = 0.05, p-value = 0.640), blood group first dose (p-value for Kruskal−Wallis test = 0.093) and second dose (p-value for Kruskal−Wallis test = 0. 268), number of drugs (Spearman rho = −0.07, p-value = 0.490), and number of chronic diseases first dose (p-value for Kruskal−Wallis test = 0.632) and second dose (p-value for Kruskal−Wallis test = 0.510). IgG antibodies to SARS-CoV-2 were intensely elevated after the second administration of the BNT162b2 vaccine. The higher the titer of anti-peptide IgG antibodies generated after the first dose of vaccine, the higher the titer generated by the second dose of vaccine (Spearman rho = 0.86, p-value < 0.001) and the total antibody titer (Spearman rho = 0.93, p-value < 0.001). Furthermore, no serious adverse effects were reported among participants, although mild to moderate adverse effects (local or systemic) were reported after both doses of the BNT162b2 vaccine, being more frequent after the first dose of the vaccine. No participants showed a positive PCR. The BNT162b2 vaccine induces a robust and rapid antibody response regardless of participant characteristics. The second dose might be especially important because of the increased immunogenicity it produces and the possible temporal distancing of the interval between doses. In general, the vaccines were well tolerated.

Waning effectiveness of BNT162b2 and ChAdOx1 covid-19 vaccines over six months since second dose: OpenSAFELY cohort study using linked electronic health records

OBJECTIVE

To estimate waning of covid-19 vaccine effectiveness over six months after second dose.

DESIGN

Cohort study, approved by NHS England.

SETTING

Linked primary care, hospital, and covid-19 records within the OpenSAFELY-TPP database.

PARTICIPANTS

Adults without previous SARS-CoV-2 infection were eligible, excluding care home residents and healthcare professionals.

EXPOSURES

People who had received two doses of BNT162b2 or ChAdOx1 (administered during the national vaccine rollout) were compared with unvaccinated people during six consecutive comparison periods, each of four weeks.

MAIN OUTCOME MEASURES

Adjusted hazard ratios for covid-19 related hospital admission, covid-19 related death, positive SARS-CoV-2 test, and non-covid-19 related death comparing vaccinated with unvaccinated people. Waning vaccine effectiveness was quantified as ratios of adjusted hazard ratios per four week period, separately for subgroups aged ≥65 years, 18-64 years and clinically vulnerable, 40-64 years, and 18-39 years.

RESULTS

1 951 866 and 3 219 349 eligible adults received two doses of BNT162b2 and ChAdOx1, respectively, and 2 422 980 remained unvaccinated. Waning of vaccine effectiveness was estimated to be similar across outcomes and vaccine brands. In the ≥65 years subgroup, ratios of adjusted hazard ratios for covid-19 related hospital admission, covid-19 related death, and positive SARS-CoV-2 test ranged from 1.19 (95% confidence interval 1.14 to 1.24)to 1.34 (1.09 to 1.64) per four weeks. Despite waning vaccine effectiveness, rates of covid-19 related hospital admission and death were substantially lower among vaccinated than unvaccinated adults up to 26 weeks after the second dose, with estimated vaccine effectiveness ≥80% for BNT162b2, and ≥75% for ChAdOx1. By weeks 23-26, rates of positive SARS-CoV-2 test in vaccinated people were similar to or higher than in unvaccinated people (adjusted hazard ratios up to 1.72 (1.11 to 2.68) for BNT162b2 and 1.86 (1.79 to 1.93) for ChAdOx1).

CONCLUSIONS

The rate at which estimated vaccine effectiveness waned was consistent for covid-19 related hospital admission, covid-19 related death, and positive SARS-CoV-2 test and was similar across subgroups defined by age and clinical vulnerability. If sustained to outcomes of infection with the omicron variant and to booster vaccination, these findings will facilitate scheduling of booster vaccination.

COVID-19 infection among vaccinated and unvaccinated: Does it make any difference?

Objective

There is a probability that vaccination may lead to reduction in the severity and complications associated with COVID-19 infection among hospitalized patients. This study aimed to determine the characteristics, clinical profiles, and outcomes of COVID-19 infection in vaccinated and non-vaccinated patients.

Design and data sources

This prospective observational cohort study was conducted at the Aga Khan University Hospital (AKUH) and recruited COVID-19 patients admitted between June 1^st and September 30^th, 2021. Patients’ demographics, date of admission and discharge, comorbid conditions, immunization status for COVID-19 infection, presenting complaints, lab workup and computed tomography (CT) scan findings were obtained from the medical records. The primary outcome of the study was patients’ condition at discharge and the secondary outcomes included level of care, length of stay (LOS), requirement of non-invasive ventilation (NIV) and inotropic support.

Results

Among a cohort of 434 patients, 37.7% (n = 164), 6.6% (n = 29) and 55.5% (n = 241) were fully vaccinated, partially vaccinated, and unvaccinated, respectively. Around 3% and 42.9% of the patient required inotropic and NIV support respectively; however, there was no discernible difference between them in terms of vaccination status. In case of unvaccinated patients there were significantly increased number of critical care admissions (p-value 0.043). Unvaccinated patients had significantly higher median serum procalcitonin, ferritin, LDH and D-dimer levels. Around 5.3% (n = 23) of the patient required invasive ventilation and it was more common in unvaccinated patients (p-value 0.04). Overall, mortality rate was 12.2% (n = 53) and this was higher (16.2%, n = 39) in unvaccinated patients as compared to fully vaccinated patients (6.1%, n = 10, p-value 0.006).

Conclusions

Through this preliminary data, we can conclude that patient can develop severe and critical COVID-19 infection despite being vaccinated but this proportion is low as compared to unvaccinated population. So, uninterrupted endeavors need to be done to vaccinate as many individuals as possible. Furthermore, more effective vaccinations need to be developed to lessen the high death toll of COVID-19 infection.

A Complementary Union of SARS-CoV2 Natural and Vaccine Induced Immune Responses

Our understanding of the immune responses that follow SARS-CoV-2 infection and vaccination has progressed considerably since the COVID-19 pandemic was first declared on the 11th of March in 2020. Recovery from infection is associated with the development of protective immune responses, although over time these become less effective against new emerging SARS-CoV-2 variants. Consequently, reinfection with SARS-CoV-2 variants is not infrequent and has contributed to the ongoing pandemic. COVID-19 vaccines have had a tremendous impact on reducing infection and particularly the number of deaths associated with SARS-CoV-2 infection. However, waning of vaccine induced immunity plus the emergence of new variants has necessitated the use of boosters to maintain the benefits of vaccination in reducing COVID-19 associated deaths. Boosting is also beneficial for individuals who have recovered from COVID-19 and developed natural immunity, also enhancing responses immune responses to SARS-CoV-2 variants. This review summarizes our understanding of the immune responses that follow SARS-CoV-2 infection and vaccination, the risks of reinfection with emerging variants and the very important protective role vaccine boosting plays in both vaccinated and previously infected individuals.

Effectiveness and protection duration of Covid-19 vaccines and previous infection against any SARS-CoV-2 infection in young adults

Data on effectiveness and protection duration of Covid-19 vaccines and previous infection against general SARS-CoV-2 infection in general populations are limited. Here we evaluate protection from Covid-19 vaccination (primary series) and previous infection in 21,261 university students undergoing repeated surveillance testing between 8/8/2021-12/04/2021, during which B.1.617 (delta) was the dominant SARS-CoV-2 variant. Estimated mRNA-1273, BNT162b2, and AD26.COV2.S effectiveness against any SARS-CoV-2 infection is 75.4% (95% CI: 70.5-79.5), 65.7% (95% CI: 61.1-69.8), and 42.8% (95% CI: 26.1-55.8), respectively. Among previously infected individuals, protection is 72.9% when unvaccinated (95% CI: 66.1-78.4) and increased by 22.1% with full vaccination (95% CI: 15.8-28.7). Statistically significant decline in protection is observed for mRNA-1273 (P < .001), BNT162b2 (P < .001), but not Ad26.CoV2.S (P = 0.40) or previous infection (P = 0.12). mRNA vaccine protection dropped 29.7% (95% CI: 17.9-41.6) six months post- vaccination, from 83.2% to 53.5%. We conclude that the 2-dose mRNA vaccine series initially offers strong protection against general SARS-CoV-2 infection caused by the delta variant in young adults, but protection substantially decreases over time. These findings indicate that vaccinated individuals may still contribute to community spread. While previous SARS-CoV-2 infection consistently provides moderately strong protection against repeat infection from delta, vaccination yields a substantial increase in protection.

Case of reactive sacroiliitis possibly induced by an mRNA coronavirus disease vaccine

A woman in her 30s received a second dose, first booster, Corminaty vaccine against the SARS-CoV-2. Three days later, the patient developed unilateral sacroiliitis. A pelvic scan revealed inflammatory joint edges, bone erosion and a heterogeneous mass of 2.5 cm in the psoas muscle. Joint puncture revealed no microcrystalline deposits, but bone marrow cells, erythroblast were identified. The standard bacterial cultures and culture for mycobacteria were negative. HLA B27 was negative, and no seroconversion was identified for HIV, Epstein-Barr virus, cytomegalovirus, chlamydia or Quantiferon. Two months later, the sacroiliitis resolved.The aetiologic approach of this erosive unilateral acute sacroiliitis in a person naïve to rheumatologic pathology was negative for inflammatory or infectious sacroiliitis. Arthralgias after vaccination are expected. Arthritis is less common, and acute sacroiliitis has not yet been described. Acute sacroiliitis may be considered a reactive sacroiliitis to the anti-COVID-19 mRNA vaccine.

Frailty and COVID-19 mRNA Vaccine Antibody Response in the COVID-19 Community Research Partnership

BACKGROUND

COVID-19 has disproportionately affected older adults. Frailty has been associated with impaired vaccine response in other vaccine types, but the impact of frailty on mRNA vaccine response is undefined.

METHODS

Observational study of adults aged 55 and older from 1 U.S. health care system between January 22, 2021 and September 16, 2021 with self-reported Moderna or Pfizer COVID-19 mRNA vaccine and an electronic frailty index (eFI) score from their medical record (n = 1 677). Participants' frailty status was compared with positive antibody detection (seroconversion) following full vaccination and subsequent loss of positive antibody detection (seroreversion) using logistic regression models.

RESULTS

Of 1 677 older adults with median (interquartile range) age, 67 (62 and 72) years, and frailty status (nonfrail: 879 [52%], prefrail: 678 [40%], and frail: 120 [7.2%]), seroconversion was not detected in 23 (1.4%) over 60 days following full vaccination. Frail individuals were less likely to seroconvert than nonfrail individuals, adjusted odds ratio (OR) 3.75, 95% confidence interval (CI; 1.04, 13.5). Seroreversion was detected in 50/1 631 individuals (3.1%) over 6 months of median follow-up antibody testing. Frail individuals were more likely to serorevert than nonfrail individuals, adjusted OR 3.02, 95% CI (1.17, 7.33).

CONCLUSION

Overall antibody response to COVID-19 mRNA vaccination was high across age and frailty categories. While antibody detection is an incomplete descriptor of vaccine response, the high sensitivity of this antibody combined with health-system data reinforce our conclusions that frailty is an independent predictor of impaired antibody response to the COVID-19 mRNA vaccines. Frailty should be considered in vaccine studies and prevention strategies.

Quantifying the immunological distinctiveness of emerging SARS-CoV-2 variants in the context of prior regional herd exposure

The COVID-19 pandemic has seen the persistent emergence of immune-evasive SARS-CoV-2 variants under the selection pressure of natural and vaccination-acquired immunity. However, it is currently challenging to quantify how immunologically distinct a new variant is compared to all the prior variants to which a population has been exposed. Here, we define "Distinctiveness" of SARS-CoV-2 sequences based on a proteome-wide comparison with all prior sequences from the same geographical region. We observe a correlation between Distinctiveness relative to contemporary sequences and future change in prevalence of a newly circulating lineage (Pearson r = 0.75), suggesting that the Distinctiveness of emergent SARS-CoV-2 lineages is associated with their epidemiological fitness. We further show that the average Distinctiveness of sequences belonging to a lineage, relative to the Distinctiveness of other sequences that occur at the same place and time (n = 944 location/time data points), is predictive of future increases in prevalence (Area Under the Curve, AUC = 0.88 [95% confidence interval 0.86 to 0.90]). By assessing the Delta variant in India versus Brazil, we show that the same lineage can have different Distinctiveness-contributing positions in different geographical regions depending on the other variants that previously circulated in those regions. Finally, we find that positions that constitute epitopes contribute disproportionately (20-fold higher than the average position) to Distinctiveness. Overall, this study suggests that real-time assessment of new SARS-CoV-2 variants in the context of prior regional herd exposure via Distinctiveness can augment genomic surveillance efforts.

Use of Recently Vaccinated Individuals to Detect Bias in Test-Negative Case-Control Studies of COVID-19 Vaccine Effectiveness

Postauthorization observational studies play a key role in understanding COVID-19 vaccine effectiveness following the demonstration of efficacy in clinical trials. Although bias due to confounding, selection bias, and misclassification can be mitigated through careful study design, unmeasured confounding is likely to remain in these observational studies. Phase III trials of COVID-19 vaccines have shown that protection from vaccination does not occur immediately, meaning that COVID-19 risk should be similar in recently vaccinated and unvaccinated individuals, in the absence of confounding or other bias. Several studies have used the estimated effectiveness among recently vaccinated individuals as a negative control exposure to detect bias in vaccine effectiveness estimates. In this paper, we introduce a theoretical framework to describe the interpretation of such a bias indicator in test-negative studies, and outline strong assumptions that would allow vaccine effectiveness among recently vaccinated individuals to serve as a negative control exposure.

Breakthrough Infections Following mRNA SARS-CoV-2 Vaccination in Kidney Transplant Recipients

BACKGROUND

The clinical effectiveness of coronavirus disease 2019 (COVID-19) vaccination in kidney transplant (KT) recipients is lower than in the general population.

METHODS

From April to October 2021, 481 KT recipients with COVID-19, included in the Spanish Society of Nephrology COVID-19 Registry, were analyzed. Data regarding vaccination status and vaccine type were collected, and outcomes of unvaccinated or partially vaccinated patients (n = 130) were compared with fully vaccinated patients (n = 351).

RESULTS

Clinical picture was similar and survival analysis showed no differences between groups: 21.7% of fully vaccinated patients and 20.8% of unvaccinated or partially vaccinated died (P = 0.776). In multivariable analysis, age and pneumonia were independent risk factors for death, whereas vaccination status was not related to mortality. These results remained similar when we excluded patients with partial vaccination, as well as when we analyzed exclusively hospitalized patients. Patients vaccinated with mRNA-1273 (n = 213) showed a significantly lower mortality than those who received the BNT162b2 vaccine (n = 121) (hazard ratio: 0.52; 95% confidence interval, 0.31-0.85; P = 0.010).

CONCLUSIONS

COVID-19 severity in KT patients has remained high and has not improved despite receiving 2 doses of the mRNA vaccine. The mRNA-1273 vaccine shows higher clinical effectiveness than BNT162b2 in KT recipients with breakthrough infections. Confirmation of these data will require further research taking into account the new variants and the administration of successive vaccine doses.

Age-related differences in symptoms in older emergency department patients with COVID-19: Prevalence and outcomes in a multicenter cohort

BACKGROUND

Older adults represent a disproportionate share of severe COVID-19 presentations and fatalities, but we have limited understanding of the differences in presentation by age and the association between less typical emergency department (ED) presentations and clinical outcomes.

METHODS

This retrospective cohort study used the RECOVER Network registry, a research collaboration of 86 EDs in 27 U.S. states. We focused on encounters with a positive nasopharyngeal swab for SARS-CoV-2, and described their demographics, clinical presentation, and outcomes. Sequential multivariable logistic regressions examined the strength of association between age cohort and outcomes.

RESULTS

Of 4536 encounters, median patient age was 55 years, 49% were women, and 34% were non-Hispanic Black persons. Cough was the most common presenting complaint across age groups (18-64, 65-74, and 75+): 71%, 67%, and 59%, respectively (p < 0.001). Neurological symptoms, particularly altered mental status, were more common in older adults (2%, 11%, 26%; p < 0.001). Patients 75+ had the greatest odds of ED index visit admission of all age groups (adjusted odds ratio [aOR] 6.66; 95% CI 5.23-8.56), 30-day hospitalization (aOR 7.44; 95% CI 5.63-9.99), and severe COVID-19 (aOR 4.26; 95% CI 3.45-5.27). Compared to individuals with alternate presentations and adjusting for age, patients with typical symptoms (fever, cough and/or shortness of breath) had similar odds of ED index visit admission (aOR 1.01; 95% CI 0.81-1.24), potentially higher odds of 30-day hospitalization (aOR 1.23; 95% CI 1.00-1.53), and greater odds of severe COVID-19 (aOR 1.46; 95% CI 1.12-1.90).

CONCLUSIONS

Older patients with COVID-19 are more likely to have presentations without the most common symptoms. However, alternate presentations of COVID-19 in older ED patients are not associated with greater odds of mechanical ventilation and/or death. Our data highlights the importance of a liberal COVID-19 testing strategy among older ED patients to facilitate accurate diagnoses and timely treatment and prophylaxis.

Vaccine Effectiveness of CanSino (Adv5-nCoV) Coronavirus Disease 2019 (COVID-19) Vaccine Among Childcare Workers-Mexico, March-December 2021

BACKGROUND

Beginning in March 2021, Mexico vaccinated childcare workers with a single-dose CanSino Biologics (Adv5-nCoV) coronavirus disease 2019 (COVID-19) vaccine. Although CanSino is currently approved for use in 10 Latin American, Asian, and European countries, little information is available about its vaccine effectiveness (VE).

METHODS

We evaluated CanSino VE within a childcare worker cohort that included 1408 childcare facilities. Participants were followed during March-December 2021 and tested through severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse-transcription polymerase chain reaction or rapid antigen test if they developed any symptom compatible with COVID-19. Vaccination status was obtained through worker registries. VE was calculated as 100% × (1 - hazard ratio for SARS-CoV-2 infection in fully vaccinated vs unvaccinated participants), using an Andersen-Gill model adjusted for age, sex, state, and local viral circulation.

RESULTS

The cohort included 43 925 persons who were mostly (96%) female with a median age of 32 years; 37 646 (86%) were vaccinated with CanSino. During March-December 2021, 2250 (5%) participants had laboratory-confirmed COVID-19, of whom 25 were hospitalized and 6 died. Adjusted VE was 20% (95% confidence interval [CI], 10%-29%) against illness, 76% (95% CI, 42%-90%) against hospitalization, and 94% (95% CI, 66%-99%) against death. VE against illness declined from 48% (95% CI, 33%-61%) after 14-60 days following full vaccination to 20% (95% CI, 9%-31%) after 61-120 days.

CONCLUSIONS

CanSino vaccine was effective at preventing COVID-19 illness and highly effective at preventing hospitalization and death. It will be useful to further evaluate duration of protection and assess the value of booster doses to prevent COVID-19 and severe outcomes.

Characterization of test positivity among patients with coronavirus disease 2019 (COVID-19) in three electronic health records databases, February-November 2020

Background

Monitoring COVID-19 testing volumes and test positivity is an integral part of the response to the pandemic. We described the characteristics of individuals who were tested and tested positive for SARS-CoV-2 during the pre-vaccine phase of the pandemic in the United States (U.S.).

Methods

This descriptive study analyzed three U.S. electronic health record (EHR) databases (Explorys, Academic Health System, and OneFlorida) between February and November 2020, identifying patients who received an interpretable nucleic acid amplification test (NAAT) result. Test-level data were used to characterize the settings in which tests were administered. Patient-level data were used to calculate test positivity rates and characterize the demographics, comorbidities, and hospitalization rates of COVID-19-positive patients.

Results

Over 40% of tests were conducted in outpatient care settings, with a median time between test order and result of 0–1 day for most settings. Patients tested were mostly female (55.6–57.7%), 18–44 years of age (33.9–41.2%), and Caucasian (44.0–66.7%). The overall test positivity rate was 13.0% in Explorys, 8.0% in Academic Health System, and 8.9% in OneFlorida. The proportion of patients hospitalized within 14 days of a positive COVID-19 NAAT result was 24.2–33.1% across databases, with patients over 75 years demonstrating the highest hospitalization rates (46.7–69.7% of positive tests).

Conclusions

This analysis of COVID-19 testing volume and positivity patterns across three large EHR databases provides insight into the characteristics of COVID-19-tested, COVID-19-test-positive, and hospitalized COVID-19-test-positive patients during the early phase of the pandemic in the U.S.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13635-6.

Comparative effectiveness and durability of COVID-19 vaccination against death and severe disease in an ongoing nationwide mass vaccination campaign

As national coronavirus disease 2019 (COVID-19) mass vaccination campaigns are rolled out, monitoring real-world Vaccine Effectiveness (VE) and its durability is essential. We aimed to estimate COVID-19 VE against severe disease and death in the Greek population, for all vaccines currently in use. Nationwide active surveillance and vaccination registry data during January-December 2021 were used to estimate VE via quasi-Poisson regression, adjusted for age and calendar time. Interaction terms were included to assess VE by age group, against the "delta" severe acute respiratory syndrome coronavirus 2 variant and waning of VE over time. Two doses of BNT162b2, mRNA-1273, or ChAdOx1 nCov-19 vaccines offered very high (>90%) VE against both intubation and death across all age groups, similar against both "delta" and previous variants, with one-dose Ad26.COV2.S slightly lower. VE waned over time but remained >80% at 6 months, and three doses increased VE again to near 100%. Vaccination prevented an estimated 19 691 COVID-19 deaths (95% confidence interval: 18 890-20 788) over the study period. All approved vaccines offer strong and also durable protection against COVID-19 severe disease and death. Every effort should be made to vaccinate the population with at least two doses, to reduce the mortality and morbidity impact of the pandemic.

Immune response to COVID-19 vaccination in a population with and without a previous SARS-CoV-2 infection

PURPOSE

To evaluate IgG production in a group of vaccinated and unvaccinated subjects previously infected, or not, with SARS-CoV-2.

METHODS

A total of 316 subjects were enrolled at different times after vaccination and/or infection. IgG against target S1 subunit of the spike protein of SARS-COV-2 was assessed by a chemiluminescent microparticle immunoassay. Participant data was collected using a clinical-epidemiological survey.

RESULTS

A total of 56.2% (n = 146) of our cohort was vaccinated, with 27.5% (n = 36) reporting a previous infection. Of these, all were IgG positive at the time of the study, regardless of gender, age category, vaccine type, and elapsed time since vaccination. The vaccinated group without a previous infection (72.5%, n = 95) showed a slightly lower IgG seropositivity and median values, overall, although significantly higher in females and lower with the ChAdOx1 nCoV-19 (AstraZeneca) vaccine. Vaccinated subjects above the age of 65 showed a trend towards higher median IgG values (13,911.0 AU/mL), when previously infected with SARS-CoV-2, but comparatively lower IgG median value (5158.7 AU/mL) in its absence. In all vaccinated groups, IgG antibody production increased at 1-2 weeks, peaking at 4-6 weeks. Afterward, IgG decreased progressively but almost all subjects (97.7%, n = 128) were seropositive for the remainder of our study. Fully vaccinated individuals with a past infection showed a lower IgG rate of decrease versus their uninfected counterparts (17.9 vs 22.6%, respectively).

CONCLUSION

Our findings suggest a higher effect of vaccination on the production IgG antibodies, as opposed to natural infection. Nonetheless, in general, antibody titers waned rapidly.

In-Hospital Mortality Among Hospitalized COVID-19 Patients in the United States: How did it change in 2021?

In this retrospective observational study in a US national sample of 501 671 adults hospitalized with coronavirus disease 2019, adjusted in-hospital mortality decreased from 12% in February 2021 to 9% in April 2021. However, adjusted in-hospital mortality increased to 16% in September and October 2021. Adjusted intensive care unit admission fluctuated between 20% and 27% in 2021.

Vaccine effectiveness and duration of protection against symptomatic infections and severe Covid-19 outcomes in adults aged 50 years and over, France, January to mid-December 2021

Background

SARS-CoV-2 continues to spread despite fast vaccine rollout, which could be attributed to waning immunity or to a reduced protection against some variants. A thorough characterization of vaccine protection and its duration in time is needed to inform vaccination policies and enhance public trust.

Methods

We linked three national databases with exhaustive information on screening, vaccination and hospitalizations in France from January 1st to December 12, 2021. We performed a two-step analysis to estimate vaccine effectiveness against severe outcomes of Covid-19 (requiring hospitalization) in people aged 50 years or over, combining: (i) a test-negative case-control design to assess vaccine effectiveness against symptomatic infections; and (ii) a survival analysis to assess the additional protection against severe outcomes (hospitalizations, ICU admissions and inpatient deaths) in infected individuals.

Findings

We found a high vaccine effectiveness in people aged 50 years or more, reaching 82% against symptomatic infections and 94% against hospitalizations, after a full vaccination scheme with the Covid-19 vaccines used in France.Vaccine effectiveness against symptomatic infections decreased over time, dropping to 53% after six months, but remained high against severe outcomes (90% after six months). The booster dose allowed restoring protection levels above 90% against symptomatic infections. Vaccine protection and its evolution in time, showed little difference against the variants that circulated prior to December 2021 in France, including the Delta variant.

Interpretation

Though vaccine immunity decreases over time, vaccination remains crucial to provide individual protection against severe outcomes requiring hospitalization. This decline can be reversed by the receipt of a booster dose.

Vaccine effectiveness against COVID-19 related hospital admission in the Netherlands: a test-negative case-control study

Introduction

Real-world vaccine effectiveness (VE) estimates are essential to identify potential groups at higher risk of break-through infections and to guide policy. We assessed the VE of COVID-19 vaccination against COVID-19 hospitalization, while adjusting and stratifying for patient characteristics.

Methods

We performed a test-negative case-control study in six Dutch hospitals. The study population consisted of adults eligible for COVID-19 vaccination hospitalized between May 1 and June 28, 2021 with respiratory symptoms. Cases were defined as patients who tested positive for SARS-CoV-2 by PCR during the first 48 h of admission or within 14 days prior to hospital admission. Controls were patients tested negative at admission and did not have a positive test during the 2 weeks prior to hospitalization. VE was calculated using multivariable logistic regression, adjusting for calendar week, sex, age, comorbidity and nursing home residency. Subgroup analysis was performed for age, sex and different comorbidities. Secondary endpoints were ICU-admission and mortality.

Results

379 cases and 255 controls were included of whom 157 (18%) were vaccinated prior to admission. Five cases (1%) and 40 controls (16%) were fully vaccinated (VE: 93%; 95% CI: 81 – 98), and 40 cases (11%) and 70 controls (27%) were partially vaccinated (VE: 70%; 95% CI: 50–82). A strongly protective effect of vaccination was found in all comorbidity subgroups. No ICU-admission or mortality were reported among fully vaccinated cases. Of unvaccinated cases, mortality was 10% and 19% was admitted at the ICU.

Conclusion

COVID-19 vaccination provides a strong protective effect against COVID-19 related hospital admission, in patients with and without comorbidity.

Clinical characteristics and respiratory care in hospitalized vaccinated SARS-CoV-2 patients

BACKGROUND

The main objective of the present study was to analyze both clinical characteristics and evolution during hospitalization of a cohort of patients admitted for COVID-19 pneumonia who were not vaccinated, or with a complete or incomplete vaccination schedule.

METHODS

This COVID-19 specialized single-center cohort study of 1888 COVID-19 patients hospitalized at the "Enfermera Isabel Zendal" Emergencies Hospital (HEEIZ), Madrid (Spain) was performed between July 1 and September 30, 2021. It compared the results of 1327 hospitalized unvaccinated patients to 209 hospitalized fully vaccinated and 352 hospitalized partially vaccinated patients. The four different COVID-19 vaccines authorized in Spain during the time-period studied were: BNT162b2 (Pfizer); ChAdOx1 nCoV-19 (AstraZeneca), mRNA-1273 (Moderna); Ad26.COV2.S (Janssen).

FINDINGS

Hospitalized patients' median age was 41 years (IQR 33-50) for the unvaccinated and 61 years (IQR 53-67) for the fully vaccinated ones. The main comorbidities were obesity, hypertension and diabetes mellitus. 20% of unvaccinated patients (266) required noninvasive respiratory care, as did 14% (51) of partially and 14% (30) of fully vaccinated; 6% (78) of the unvaccinated patients also needed invasive respiratory care, as did 5% (16) of partially and 11 (5%) fully vaccinated.

INTERPRETATION

Fully vaccinated patients were 84% (95% CI: 82-86%) less likely to be admitted to hospital, and protection rose for those aged <50 years. Once hospitalized, vaccinated patients displayed more protection against requiring respiratory care than unvaccinated ones, despite being older and having more comorbidities. No differences appeared for the four studied COVID-19 vaccines and complying with vaccination recommendations proved relevant.

FUNDING

The research was funded by the "Plan Propio de Investigación" Program of the Castilla-La Mancha University /European Regional Development Fund (2021-GRIN-31,039).

A Systematic Review of Coronavirus Disease 2019 Vaccine Efficacy and Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2 Infection and Disease

Billions of doses of coronavirus disease 2019 (COVID-19) vaccines have been administered globally, dramatically reducing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) incidence and severity in some settings. Many studies suggest vaccines provide a high degree of protection against infection and disease, but precise estimates vary and studies differ in design, outcomes measured, dosing regime, location, and circulating virus strains. In this study, we conduct a systematic review of COVID-19 vaccines through February 2022. We included efficacy data from Phase 3 clinical trials for 15 vaccines undergoing World Health Organization Emergency Use Listing evaluation and real-world effectiveness for 8 vaccines with observational studies meeting inclusion criteria. Vaccine metrics collected include protection against asymptomatic infection, any infection, symptomatic COVID-19, and severe outcomes including hospitalization and death, for partial or complete vaccination, and against variants of concern Alpha, Beta, Gamma, Delta, and Omicron. We additionally review the epidemiological principles behind the design and interpretation of vaccine efficacy and effectiveness studies, including important sources of heterogeneity.

Effectiveness of complete primary vaccination against COVID-19 at primary care and community level during predominant Delta circulation in Europe: multicentre analysis, I-MOVE-COVID-19 and ECDC networks, July to August 2021

IntroductionIn July and August 2021, the SARS-CoV-2 Delta variant dominated in Europe.AimUsing a multicentre test-negative study, we measured COVID-19 vaccine effectiveness (VE) against symptomatic infection.MethodsIndividuals with COVID-19 or acute respiratory symptoms at primary care/community level in 10 European countries were tested for SARS-CoV-2. We measured complete primary course overall VE by vaccine brand and by time since vaccination.ResultsOverall VE was 74% (95% CI: 69-79), 76% (95% CI: 71-80), 63% (95% CI: 48-75) and 63% (95% CI: 16-83) among those aged 30-44, 45-59, 60-74 and ≥ 75 years, respectively. VE among those aged 30-59 years was 78% (95% CI: 75-81), 66% (95% CI: 58-73), 91% (95% CI: 87-94) and 52% (95% CI: 40-61), for Comirnaty, Vaxzevria, Spikevax and COVID-19 Vaccine Janssen, respectively. VE among people 60 years and older was 67% (95% CI: 52-77), 65% (95% CI: 48-76) and 83% (95% CI: 64-92) for Comirnaty, Vaxzevria and Spikevax, respectively. Comirnaty VE among those aged 30-59 years was 87% (95% CI: 83-89) at 14-29 days and 65% (95% CI: 56-71%) at ≥ 90 days between vaccination and onset of symptoms.ConclusionsVE against symptomatic infection with the SARS-CoV-2 Delta variant varied among brands, ranging from 52% to 91%. While some waning of the vaccine effect may be present (sample size limited this analysis to only Comirnaty), protection was 65% at 90 days or more between vaccination and onset.

Serious Underlying Medical Conditions and COVID-19 Vaccine Hesitancy: A Large Cross-Sectional Analysis from Australia

As COVID-19 vaccinations became available and were proven effective in preventing serious infection, uptake amongst individuals varied, including in medically vulnerable populations. This cross-sectional multi-site study examined vaccine uptake, hesitancy, and explanatory factors amongst people with serious and/or chronic health conditions, including the impact of underlying disease on attitudes to vaccination. A 42-item survey was distributed to people with cancer, diabetes, or multiple sclerosis across ten Australian health services from 30 June to 5 October 2021. The survey evaluated sociodemographic and disease-related characteristics and incorporated three validated scales measuring vaccine hesitancy and vaccine-related beliefs generally and specific to their disease: the Oxford COVID-19 Vaccine Hesitancy Scale, the Oxford COVID-19 Vaccine Confidence and Complacency Scale and the Disease Influenced Vaccine Acceptance Scale-Six. Among 4683 participants (2548 [54.4%] female, 2108 [45.0%] male, 27 [0.6%] other; mean [SD] age, 60.6 [13.3] years; 3560 [76.0%] cancer, 842 [18.0%] diabetes, and 281 [6.0%] multiple sclerosis), 3813 (81.5%) self-reported having at least one COVID-19 vaccine. Unvaccinated status was associated with younger age, female sex, lower education and income, English as a second language, and residence in regional areas. Unvaccinated participants were more likely to report greater vaccine hesitancy and more negative perceptions toward vaccines. Disease-related vaccine concerns were associated with unvaccinated status and hesitancy, including greater complacency about COVID-19 infection, and concerns relating to vaccine efficacy and impact on their disease and/or treatment. This highlights the need to develop targeted strategies and education about COVID-19 vaccination to support medically vulnerable populations and health professionals.

Risk Factors Associated With SARS-CoV-2 Breakthrough Infections in Fully mRNA-Vaccinated Individuals: Retrospective Analysis

BACKGROUND

COVID-19 messenger RNA (mRNA) vaccines have demonstrated efficacy and effectiveness in preventing symptomatic COVID-19, while being relatively safe in trial studies. However, vaccine breakthrough infections have been reported.

OBJECTIVE

This study aims to identify risk factors associated with COVID-19 breakthrough infections among fully mRNA-vaccinated individuals.

METHODS

We conducted a series of observational retrospective analyses using the electronic health records (EHRs) of the Columbia University Irving Medical Center/New York Presbyterian (CUIMC/NYP) up to September 21, 2021. New York City (NYC) adult residences with at least 1 polymerase chain reaction (PCR) record were included in this analysis. Poisson regression was performed to assess the association between the breakthrough infection rate in vaccinated individuals and multiple risk factors-including vaccine brand, demographics, and underlying conditions-while adjusting for calendar month, prior number of visits, and observational days in the EHR.

RESULTS

The overall estimated breakthrough infection rate was 0.16 (95% CI 0.14-0.18). Individuals who were vaccinated with Pfizer/BNT162b2 (incidence rate ratio [IRR] against Moderna/mRNA-1273=1.66, 95% CI 1.17-2.35) were male (IRR against female=1.47, 95% CI 1.11-1.94) and had compromised immune systems (IRR=1.48, 95% CI 1.09-2.00) were at the highest risk for breakthrough infections. Among all underlying conditions, those with primary immunodeficiency, a history of organ transplant, an active tumor, use of immunosuppressant medications, or Alzheimer disease were at the highest risk.

CONCLUSIONS

Although we found both mRNA vaccines were effective, Moderna/mRNA-1273 had a lower incidence rate of breakthrough infections. Immunocompromised and male individuals were among the highest risk groups experiencing breakthrough infections. Given the rapidly changing nature of the SARS-CoV-2 pandemic, continued monitoring and a generalizable analysis pipeline are warranted to inform quick updates on vaccine effectiveness in real time.

Evaluation of the Real-World Effectiveness of Vaccines against COVID-19 at a Local Level: Protocol for a Test-Negative Case-Control Study

Vaccines against COVID-19 approved for use in the EU/EEA have been shown to be highly effective against wild-type SARS-CoV-2. However, their effectiveness against new variants may be reduced. This study aims to evaluate the effectiveness of vaccines against COVID-19 in the prevention of symptomatic and severe disease, during pre- and post-omicron phases. Individuals who sought treatment at the emergency department of a Portuguese hospital with COVID-19-like disease and were tested for SARS-CoV-2 are the subjects of the study. Patients who received a positive result are considered cases, while those with negative results are the controls. The test-negative case–control method is one of the study designs recommended by WHO to estimate the effectiveness of vaccines against COVID-19. The main advantage of this design is that it controls for the healthcare seeking bias, commonly present in traditional cohort and case–control designs. This study may have broad implications for understanding the real-world performance of the COVID-19 vaccines at the local level, which may play a key role in promoting adherence to vaccination. Moreover, this study may contribute to inform decisions regarding booster doses and variant-specific vaccine formulations leading to the control of this and future pandemics.

Durability analysis of the highly effective mRNA-1273 vaccine against COVID-19

COVID-19 vaccines are effective, but breakthrough infections have been increasingly reported. We conducted a test-negative case-control study to assess the durability of protection against symptomatic infection after vaccination with mRNA-1273. We fit conditional logistic regression (CLR) models stratified on residential county and calendar date of SARS-CoV-2 PCR testing to assess the association between the time elapsed since vaccination and the odds of symptomatic infection, adjusted for several covariates. There were 2,364 symptomatic individuals who had a positive SARS-CoV-2 PCR test after full vaccination with mRNA-1273 ("cases") and 12,949 symptomatic individuals who contributed 15,087 negative tests after full vaccination ("controls"). The odds of symptomatic infection were significantly higher 250 days after full vaccination compared to the date of full vaccination (Odds Ratio [OR]: 2.47, 95% confidence interval [CI]: 1.19-5.13). The odds of non-COVID-19 associated hospitalization and non-COVID-19 pneumonia (negative control outcomes) remained relatively stable over the same time interval (Day 250 OR_{Non-COVID Hospitalization}: 0.68, 95% CI: 0.47-1.0; Day 250 OR_{Non-COVID Pneumonia}: 1.11, 95% CI: 0.24-5.2). The odds of symptomatic infection remained significantly lower almost 300 days after the first mRNA-1273 dose as compared to 4 days after the first dose, when immune protection approximates the unvaccinated state (OR: 0.26, 95% CI: 0.17-0.39). Low rates of COVID-19 associated hospitalization or death in this cohort precluded analyses of these severe outcomes. In summary, mRNA-1273 robustly protected against symptomatic SARS-CoV-2 infection at least 8 months after full vaccination, but the degree of protection waned over this time period.

COVID-19 Vaccine Effectiveness at a Referral Hospital in Northern Peru: A Retrospective Cohort Study

COVID-19 vaccines have achieved a significant reduction in mortality, yet objective estimates are needed in specific settings. We aimed to determine the effectiveness of COVID-19 vaccination at a referral hospital in Lambayeque, Peru. We conducted a retrospective cohort study from February to September 2021. We included hospitalized patients with COVID-19, whose data were stored in NotiWeb, a patient data system of the Peruvian Ministry of Health. We applied a propensity score-weighting method according to baseline characteristics of patients, and estimated hazard ratios (HR) using Cox regression models. Of 1553 participants, the average age was 55 years (SD: 16.8), 907 (58%) were male, and 592 (38%) deceased at 28-day follow-up. Before hospital admission, 74 (4.8%) had been immunized with at least one vaccine dose. Effectiveness against death in vaccinated patients was 50% at 90-day follow-up (weighted HR 0.50, 95% CI 0.28–0.89). Our results support the effectiveness of COVID-19 vaccination against death and provide information after early immunization in Peru.

Real-World Effectiveness of the mRNA COVID-19 Vaccines in Japan: A Case–Control Study

The real-world effectiveness of the coronavirus disease 2019 (COVID-19) vaccines in Japan remains unclear. This case–control study evaluated the vaccine effectiveness (VE) of two doses of mRNA vaccine, BNT162b2 or mRNA-1273, against the delta (B.1.617.2) variant in the Japanese general population in the period June–September 2021. Individuals in close contact with COVID-19 patients were tested using polymerase chain reaction (PCR). A self-administered questionnaire evaluated vaccination status, demographic data, underlying medical conditions, lifestyle, personal protective health behaviors, and living environment. Two vaccine doses were reported by 11.6% of cases (n = 389) and 35.2% of controls (n = 179). Compared with controls, cases were younger and had a lower proportion who always performed handwashing for ≥20 s, a higher proportion of alcohol consumers, and a lower proportion of individuals living in single-family homes or with commuting family members. After adjusting for these confounding factors and day of PCR testing by multivariate logistic regression analysis, the VE in the period June–July (delta variant proportion 45%) was 92% and 79% in the period August–September (delta variant proportion 89%). The adjusted VE for homestay, hotel-based isolation and quarantine, and hospitalization was 78%, 77%, and 97%, respectively. Despite declining slightly, VE against hospitalization remained robust for ~3 months after the second dose. Vaccination policymaking will require longer-term monitoring of VE against new variants.

Long-Term Immunity and Antibody Response: Challenges for Developing Efficient COVID-19 Vaccines

Questions and concerns regarding the efficacy and immunogenicity of coronavirus disease 2019 (COVID-19) vaccines have plagued scientists since the BNT162b2 mRNA vaccine was introduced in late 2020. As a result, decisions about vaccine boosters based on breakthrough infection rates and the decline of antibody titers have commanded worldwide attention and research. COVID-19 patients have displayed continued severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-spike-protein-specific antibodies and neutralizing antibodies in longitudinal studies; in addition, cytokine activation has been detected at early steps following SARS-CoV-2 infection. Epitopes that are highly reactive and can mediate long-term antibody responses have been identified at the spike and ORF1ab proteins. The N-terminal domain of the S1 and S2 subunits is the location of important SARS-CoV-2 spike protein epitopes. High sequence identity between earlier and newer variants of SARS-CoV-2 and different degrees of sequence homology among endemic human coronaviruses have been observed. Understanding the extent and duration of protective immunity is consequential for determining the course of the COVID-19 pandemic. Further knowledge of memory responses to different variants of SARS-CoV-2 is needed to improve the design of the vaccine.

Implications of COVID-19 Vaccination on Hospital Encounters and Outcomes

Adverse events, including cardiac involvement, after vaccination for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported. We sought to evaluate trends of hospital encounters for vaccine recipients before and after vaccination. We analyzed patients who received the coronavirus disease 2019 (COVID-19) vaccine in the MedStar Health system (11 hospitals in Washington, District of Columbia and Maryland) from December 2020 through August 2021. We then compared hospital encounters (emergency department visits) of patients 60 days before a vaccine dose and 30 days after a vaccine dose, along with encounters related to the SARS-CoV-2 infection itself. The cohort included 5,217 patients who were vaccinated against COVID-19. Our analysis revealed a total of 6,751 emergency department visits, and we divided this total into 3 cohorts: fully vaccinated (n = 1,779), in vaccination window (n = 1,420), and before vaccination (n = 3,552). We found no significant association between vaccination and rate of presentation for acute coronary syndrome, pericarditis, myocarditis, heart failure, conduction abnormality, or noncardiac conditions. Further, encounters for complications related to SARS-CoV-2 infection decreased significantly from those before vaccination (5.4%) to those in vaccination window (4.2%) to those who were fully vaccinated (1.6%). These findings were consistent when all vaccinated encounters were combined into 1 cohort (fully vaccinated + in vaccination window). In conclusion, our analysis suggests that there is no significant association of COVID-19 vaccination with the rate of hospital encounters for cardiac disease, including acute coronary syndrome, pericarditis, myocarditis, congestive heart failure, and conduction abnormality. Further, administration of the vaccine resulted in a significant decrease in hospital encounters for SARS-CoV-2 infections and associated complications.

Estimands and Estimation of COVID-19 Vaccine Effectiveness Under the Test-Negative Design: Connections to Causal Inference

The test-negative design is routinely used for the monitoring of seasonal flu vaccine effectiveness. More recently, it has become integral to the estimation of COVID-19 vaccine effectiveness, in particular for more severe disease outcomes. Because the design has many important advantages and is becoming a mainstay for monitoring postlicensure vaccine effectiveness, epidemiologists and biostatisticians may be interested in further understanding the effect measures being estimated in these studies and connections to causal effects. Logistic regression is typically applied to estimate the conditional risk ratio but relies on correct outcome model specification and may be biased in the presence of effect modification by a confounder. We give and justify an inverse probability of treatment weighting (IPTW) estimator for the marginal risk ratio, which is valid under effect modification. We use causal directed acyclic graphs, and counterfactual arguments under assumptions about no interference and partial interference to illustrate the connection between these statistical estimands and causal quantities. We conduct a simulation study to illustrate and confirm our derivations and to evaluate the performance of the estimators. We find that if the effectiveness of the vaccine varies across patient subgroups, the logistic regression can lead to misleading estimates, but the IPTW estimator can produce unbiased estimates. We also find that in the presence of partial interference both estimators can produce misleading estimates.

Data-driven multiscale modelling and analysis of COVID-19 spatiotemporal evolution using explainable AI

To quantificationally identify the optimal control measures for regulators to best minimize COVID-19′s growth (G-rate) and death (D-rate) rates in today's context, this paper develops a top-down multiscale engineering approach which encompasses a series of systematic analyses, namely: (global scale) predictive modelling of G-rate and D-rate due to COVID-19 globally, followed by determining the most effective control factors which can best minimize both parameters over time via explainable Artificial Intelligence (AI) with SHAP (SHapley Additive exPlanations) method; (continental scale) same predictive forecasting of G-rate and D-rate in all continents, followed by performing explainable SHAP analysis to determine the most effective control factors for the respective continents; and (country scale) clustering the different countries (> 150 in total) into 3 main clusters to identify the universal set of effective control measures. By using the historical period between 2 May 2020 and 1 Oct 2021, the average MAPE scores for forecasting G-rate and D-rate are within 10%, or less on average, at the global and continental scales. Systematically, we have quantificationally demonstrated that the top 3 most effective control measures for regulators to best minimize G-rate universally are COVID-CONTACT-TRACING, PUBLIC-GATHERING-RULES, and COVID-STRINGENCY-INDEX, while the control factors relating to D-rate depend on the modelling scenario.

Vaccine-induced immune thrombotic thrombocytopenia and patients with cancer

Vaccines to combat SARS-CoV-2 infection and the COVID-19 pandemic were quickly developed due to significant and combined efforts by the scientific community, government agencies, and private sector pharmaceutical and biotechnology companies. Following vaccine development, which took less than a year to accomplish, randomized placebo controlled clinical trials enrolled almost 100,000 people, demonstrating efficacy and no major safety signals. Vaccination programs were started, but shortly thereafter a small number of patients with a constellation of findings including thrombosis in unusual locations, thrombocytopenia, elevated D-dimer and often low fibrinogen led another intense and concentrated scientific effort to understand this syndrome. It was recognized that this occurred within a short time following administration of adenoviral vector SARS-CoV-2 vaccines. Critical to the rapid understanding of this syndrome was prompt communication among clinicians and scientists and exchange of knowledge. Now known as vaccine-induced immune thrombotic thrombocytopenia syndrome (VITT), progress has been made in understanding the pathophysiology of the syndrome, with the development of diagnostic criteria, and most importantly therapeutic strategies needed to effectively treat this rare complication of adenoviral vector vaccination. This review will focus on the current understanding of the pathophysiology of VITT, the findings that affected patients present with, and the rational for therapies, including for patients with cancer, as prompt recognition, diagnosis, and treatment of this syndrome has resulted in a dramatic decrease in associated mortality.

Third dose vaccination with mRNA-1273 or BNT162b2 vaccines improves protection against SARS-CoV-2 infection

As of 2021 November 29, booster vaccination against SARS-CoV-2 infection has been recommended for all individuals aged 18 years and older in the United States. A key reason for this recommendation is the expectation that a booster vaccine dose can alleviate observed waning of vaccine effectiveness (VE). Although initial reports of booster effectiveness have been positive, the level of protection from booster vaccination is unclear. We conducted two studies to assess the impact of booster vaccination, with BNT162b2 or mRNA-1273, on the incidence of SARS-CoV-2 infection between August and December 2021. We first compared SARS-CoV-2 infection incidence in cohorts of 3-dose vaccine recipients to incidence in matched cohorts of 2-dose vaccine recipients (cohort size = 24,539 for BNT162b2 and 14,004 for mRNA-1273). Additionally, we applied a test-negative study design to compare the level of protection against symptomatic infection in 3-dose recipients to that observed in recent 2-dose primary vaccine series recipients. The 3-dose recipients experienced a significantly lower incidence rate of SARS-CoV-2 infection than the matched 2-dose cohorts (BNT162b2 Incidence Rate Ratio: 0.11, 95% CI: 0.09 to 0.13 and mRNA-1273 IRR: 0.11, 95% CI: 0.08 to 0.15). Results from the test-negative study showed the third vaccine dose mitigated waning of VE, with the risk of symptomatic infection in 3-dose recipients being comparable to that observed 7 to 73 days after the primary vaccine series. These results show that 3-dose vaccine regimens with BNT162b2 or mRNA-1273 are effective at reducing SARS-CoV-2 infection and support the widespread administration of booster vaccine doses.

Risk and Outcome of Breakthrough COVID-19 Infections in Vaccinated Patients With Cancer: Real-World Evidence From the National COVID Cohort Collaborative

PURPOSE

To provide real-world evidence on risks and outcomes of breakthrough COVID-19 infections in vaccinated patients with cancer using the largest national cohort of COVID-19 cases and controls.

METHODS

We used the National COVID Cohort Collaborative (N3C) to identify breakthrough infections between December 1, 2020, and May 31, 2021. We included patients partially or fully vaccinated with mRNA COVID-19 vaccines with no prior SARS-CoV-2 infection record. Risks for breakthrough infection and severe outcomes were analyzed using logistic regression.

RESULTS

A total of 6,860 breakthrough cases were identified within the N3C-vaccinated population, among whom 1,460 (21.3%) were patients with cancer. Solid tumors and hematologic malignancies had significantly higher risks for breakthrough infection (odds ratios [ORs] = 1.12, 95% CI, 1.01 to 1.23 and 4.64, 95% CI, 3.98 to 5.38) and severe outcomes (ORs = 1.33, 95% CI, 1.09 to 1.62 and 1.45, 95% CI, 1.08 to 1.95) compared with noncancer patients, adjusting for age, sex, race/ethnicity, smoking status, vaccine type, and vaccination date. Compared with solid tumors, hematologic malignancies were at increased risk for breakthrough infections (adjusted OR ranged from 2.07 for lymphoma to 7.25 for lymphoid leukemia). Breakthrough risk was reduced after the second vaccine dose for all cancers (OR = 0.04; 95% CI, 0.04 to 0.05), and for Moderna's mRNA-1273 compared with Pfizer's BNT162b2 vaccine (OR = 0.66; 95% CI, 0.62 to 0.70), particularly in patients with multiple myeloma (OR = 0.35; 95% CI, 0.15 to 0.72). Medications with major immunosuppressive effects and bone marrow transplantation were strongly associated with breakthrough risk among the vaccinated population.

CONCLUSION

Real-world evidence shows that patients with cancer, especially hematologic malignancies, are at higher risk for developing breakthrough infections and severe outcomes. Patients with vaccination were at markedly decreased risk for breakthrough infections. Further work is needed to assess boosters and new SARS-CoV-2 variants.

SARS-CoV-2 Vaccine Alpha and Delta Variant Breakthrough Infections Are Rare and Mild but Can Happen Relatively Early after Vaccination

(1) Background: Some COVID-19 vaccine recipients show breakthrough infection. It remains unknown, which factors contribute to risks and severe outcomes. Our aim was to identify risk factors for SCoV2 breakthrough infections in fully vaccinated individuals. (2) Methods: We conducted a retrospective case-control study from 28 December 2020 to 25 October 2021. Data of all patients with breakthrough infection was compared to data of all vaccine recipients in the Canton of Basel-City, Switzerland. Further, breakthrough infections by Alpha- and Delta-variants were compared. (3) Results: Only 0.39% (488/126,586) of all vaccine recipients suffered from a breakthrough infection during the observational period, whereof most cases were asymptomatic or mild (97.2%). Breakthrough infections after full vaccination occurred in the median after 78 days (IQR 47-123.5). Factors with lower odds for breakthrough infection were age (OR 0.987) and previous COVID-19 infection prior to vaccination (OR 0.296). Factors with higher odds for breakthrough infection included vaccination with Pfizer/BioNTech instead of Moderna (OR 1.459), chronic disease (OR 2.109), and healthcare workers (OR 1.404). (4) Conclusions: Breakthrough infections are rare and mild but can occur early after vaccination. This implies that booster vaccination might be initiated earlier, especially for risk groups. Due to new variants emerging repeatedly, continuous monitoring of breakthrough infections is crucial.