Facing the Omicron variant-how well do vaccines protect against mild and severe COVID-19? Third interim analysis of a living systematic review

Safety, tolerability, viral kinetics, and immune correlates of protection in healthy, seropositive UK adults inoculated with SARS-CoV-2: a single-centre, open-label, phase 1 controlled human infection study

BACKGROUND

A SARS-CoV-2 controlled human infection model (CHIM) has been successfully established in seronegative individuals using a dose of 1×101 50% tissue culture infectious dose (TCID50) pre-alpha SARS-CoV-2 virus. Given the increasing prevalence of seropositivity to SARS-CoV-2, a CHIM that could be used for vaccine development will need to induce infection in those with pre-existing immunity. Our aim was to find a dose of pre-alpha SARS-CoV-2 virus that induced infection in previously infected individuals.

METHODS

Healthy, UK volunteers aged 18-30 years, with proven (quantitative RT-PCR or lateral flow antigen test) previous SARS-CoV-2 infection (with or without vaccination) were inoculated intranasally in a stepwise dose escalation CHIM with either 1×101, 1×102, 1×10³, 1×104, or 1×105 TCID50 SARS-CoV-2/human/GBR/484861/2020, the same virus used in the seronegative CHIM. Post-inoculation, volunteers were quarantined in functionally negative pressure rooms (Oxford, UK) for 14 days and until 12-hourly combined oropharyngeal-nasal swabs were negative for viable virus by focus-forming assay. Outpatient follow-up continued for 12 months post-enrolment, with additional visits for those who developed community-acquired SARS-CoV-2 infection. The primary objective was to identify a safe, well tolerated dose that induced infection (defined as two consecutive SARS-CoV-2 positive PCRs starting 24 h after inoculation) in 50% of seropositive volunteers. This study is registered with ClinicalTrials.gov (NCT04864548); enrolment and follow-up to 12 months post-enrolment are complete.

FINDINGS

Recruitment commenced on May 6, 2021, with the last volunteer enrolled into the dose escalation cohort on Nov 24, 2022. 36 volunteers were enrolled, with four to eight volunteers inoculated in each dosing group from 1×101 to 1×105 TCID50 SARS-CoV-2. All volunteers have completed quarantine, with follow-up to 12 months complete. Despite dose escalation to 1×105 TCID50, we were unable to induce sustained infection in any volunteers. Five (14%) of 36 volunteers were considered to have transient infection, based on the kinetic of their PCR-positive swabs. Transiently infected volunteers had significantly lower baseline mucosal and systemic SARS-CoV-2-specific antibody titres and significantly lower peripheral IFNγ responses against a CD8+ T-cell SARS-CoV-2 peptide pool than uninfected volunteers. 14 (39%) of 36 volunteers subsequently developed breakthrough infection with the omicron variant after discharge from quarantine. Most adverse events reported by volunteers in quarantine were mild, with fatigue (16 [44%]) and stuffy nose (16 [44%]) being the most common. There were no serious adverse events.

INTERPRETATION

Our study demonstrates potent protective immunity induced by homologous vaccination and homologous or heterologous previous SARS-CoV-2 infection. The community breakthrough infections seen with the omicron variant supports the use of newer variants to establish a model with sufficient rate of infection for use in vaccine and therapeutic development.

FUNDING

Wellcome Trust and Department for Health and Social Care.

Needs and feasibility of living systematic reviews (LSRs): Experience from LSRs on COVID-19 vaccine effectiveness

During 2021 and 2023, a team of researchers at the Robert Koch Institute (RKI) and partnering institutions conducted two living systematic reviews (LSRs) on the effectiveness of COVID-19 vaccines in different age groups to inform recommendations of the Standing Committee on Vaccination in Germany (Ständige Impfkommission, STIKO). Based on our experience from the realization of these LSRs, we developed certain criteria to assess the needs and feasibility of conducting LSRs. Combining these with previously established criteria, we developed the following set to inform future planning of LSRs for STIKO: Needs criterion (N)1: Relevance of the research question, N2: Certainty of evidence (CoE) at baseline; N3: Expected need for Population-Intervention-Comparator-Outcome (PICO) adaptations; N4: Expected new evidence over time; N5: Expected impact of new evidence on CoE; Feasibility criterion (F)1: Availability of sufficient human resources; F2: Feasibility of timely dissemination of the results to inform decision-making. For each criterion we suggest rating options which may support the decision to conduct an LSR or other forms of evidence synthesis when following the provided flowchart. The suggested criteria were developed on the basis of the experiences from exemplary reviews in a specific research field (i.e., COVID-19 vaccination), and did not follow a formal development or validation process. However, these criteria might also be useful to assess whether questions from other research fields can and should be answered using the LSR approach, or assist in determining whether the use of an LSR is sensible and feasible for specific questions in health policy and practice.

Comparison of SARS-CoV-2 spike-specific IgA and IgG in nasal secretions, saliva and serum

Introduction

Several novel vaccine platforms aim at mucosal immunity in the respiratory tract to block SARS-CoV-2 transmission. Standardized methods for mucosal sample collection and quantification of mucosal antibodies are therefore urgently needed for harmonized comparisons and interpretations across mucosal vaccine trials and real-world data.

Methods

Using commercial electrochemiluminescence antibody panels, we compared SARS-CoV-2 spike-specific IgA and IgG in paired saliva, nasal secretions, and serum from 1048 healthcare workers with and without prior infection.

Results

Spike-specific IgA correlated well in nasal secretions and saliva (r>0.65, p<0.0001), but the levels were more than three-fold higher in nasal secretions as compared to in saliva (p<0.01). Correlations between the total population of spike-specific IgA and spike-specific secretory IgA (SIgA) were significantly stronger (p<0.0001) in nasal secretions (r=0.96, p<0.0001) as opposed to in saliva (r=0.77, p<0.0001), and spike-specific IgA correlated stronger (p<0.0001) between serum and saliva (r=0.73, p<0.001) as opposed to between serum and nasal secretions (r=0.54, p<0.001), suggesting transudation of monomeric spike specific IgA from the circulation to saliva. Notably, spike-specific SIgA had a markedly higher SARS-CoV-2 variant cross-binding capacity as compared to the total population of spike specific IgA and IgG in both nasal secretions, saliva and serum, (all p<0.0001), which emphasizes the importance of taking potential serum derived monomeric IgA into consideration when investigating mucosal immune responses.

Discussion

Taken together, although spike-specific IgA can be reliably measured in both nasal secretions and saliva, our findings imply an advantage of higher levels and likely also a larger proportion of SIgA in nasal secretions as compared to in saliva. We further corroborate the superior variant cross-binding capacity of SIgA in mucosal secretions, highlighting the potential protective benefits of a vaccine targeting the upper respiratory tract.

Results of the Cologne Corona Surveillance (CoCoS) project- a cross-sectional study: survey data on risk factors of SARS-CoV-2 infection, and moderate-to-severe course in primarily immunized adults

BACKGROUND

Amidst the COVID-19 pandemic, vaccination has been a crucial strategy for mitigating transmission and disease severity. However, vaccine-effectiveness may be influenced by various factors, including booster vaccination, as well as personal factors such as age, sex, BMI, smoking, and comorbidities. To investigate the potential effects of these factors on SARS-CoV-2 infection and disease severity, we analyzed data from the third round of the Cologne Corona Surveillance (CoCoS) project, a large cross-sectional survey.

METHODS

The study was conducted mid-February to mid-March 2022 in Cologne, Germany. A random sample of 10,000 residents aged 18 years and older were invited to participate in an online survey. Information on participants' demographics (age, sex), SARS-CoV-2 infections, vaccination status, smoking, and preexisting medical conditions were collected. The outcomes of the study were: (1) the occurrence of SARS-CoV-2 infection despite vaccination (breakthrough infection) and (2) the occurrence of moderate-to-severe disease as a result of a breakthrough infection. Cox proportional-hazards regression was used to investigate possible associations between the presence/absence of booster vaccination, personal factors and the occurrence of SARS-CoV-2 infection. Associations with moderate-to-severe infection were analyzed using the Fine and Gray subdistribution hazard model.

RESULTS

A sample of 2,991 residents responded to the questionnaire. A total of 2,623 primary immunized participants were included in the analysis of breakthrough infection and 2,618 in the analysis of SARS-CoV-2 infection severity after exclusions due to incomplete data. The multivariable results show that booster vaccination (HR = 0.613, 95%CI 0.415-0.823) and older age (HR = 0.974, 95%CI 0.966-0.981) were associated with a reduced hazard of breakthrough infection. Regarding the severity of breakthrough infection, older age was associated with a lower risk of moderate-to-severe breakthrough infection (HR = 0.962, 95%CI0.949-0.977). Female sex (HR = 2.570, 95%CI1.435-4.603), smoking (HR = 1.965, 95%CI1.147-3.367) and the presence of chronic lung disease (HR = 2.826, 95%CI1.465-5.450) were associated with an increased hazard of moderate-to-severe breakthrough infection.

CONCLUSION

The results provide a first indication of which factors may be associated with SARS-CoV-2 breakthrough infection and moderate-to-severe course of infection despite vaccination. However, the retrospective nature of the study and risk of bias in the reporting of breakthrough infection severity limit the strength of the results.

TRIAL REGISTRATION

DRKS.de, German Clinical Trials Register (DRKS), Identifier: DRKS00024046, Registered on 25 February 2021.

Application of the screening method for estimating COVID-19 vaccine effectiveness using routine surveillance data: Germany's experience during the COVID-19 pandemic, July 2021 to March 2023

The screening method represents a simple, quick, and practical tool for estimating vaccine effectiveness (VE) using routine disease surveillance and vaccine coverage data, even if these data cannot be linked. In Germany, where notification data, laboratory testing data, and vaccine coverage data cannot be linked due to strict data protection requirements, the screening method was used to assess COVID-19 VE continuously between July 2021 and March 2023. During this period, when Delta and Omicron variants circulated, VE estimates were produced in real-time for different age groups and clinical outcomes. Here we describe the country's overall positive experience using the screening method, including its strengths and limitations, and provide practical guidance regarding a few issues, such as case definition stringency, testing behaviour, and data stratification, that require careful consideration during data analysis and the interpretation of the results.

Effect of the number of coronavirus disease 2019 (COVID-19) vaccination shots on the occurrence of pneumonia, severe pneumonia, and death in SARS-CoV-2-infected patients

Background

Coronavirus disease (COVID-19) has posed a significant threat to the lives and health of people worldwide since its onset in 2019. However, the relationship between the number of vaccination shots and the severity of SARS-CoV-2 infection in Chinese patients remains unclear.

Methods

We retrospectively collected information from 829 patients infected with SARS-CoV-2 in Ningbo Medical Center Lihuili Hospital from December 05, 2022 to March 31, 2023, then divided them into four groups based on the severity of pneumonia. Last, we compared the difference in the number of shots of COVID-19 vaccine between the four groups, considering potential confounding factors using univariate and multivariate logistic regression.

Results

Vaccination with two and three doses was positively associated with low prevalence of pneumonia and severe pneumonia both in crude and optimal models, while only three doses of the vaccine was correlated with low prevalence of death in SARS-CoV-2-infected patients. In optimal models, male SARS-CoV-2-infected individuals with advanced age were positively associated with high prevalence of pneumonia, severe pneumonia, and death; comorbidity with hypertension (OR = 2.532, p < 0.001) was positively associated with high prevalence of pneumonia (OR = 2.532, p < 0.001); and comorbidity with diabetes was positively associated with high prevalence of death (OR = 1.856, p = 0.011). However, this is a cross-sectional study and the causal relationships need to be further studied.

Conclusion

One dose of vaccine may not have a protective effect against pneumonia, severe pneumonia, and death; more than one dose of vaccine is an independent protective factor for pneumonia and severe pneumonia; and three doses of vaccine is an independent protective factor for death.

Long-Term Trends in the Protection Against Severe Courses of COVID-19 by Vaccination

BACKGROUND

The long-term course of protection against severe COVID-19 courses by vaccine-induced or hybrid immunity in Germany is unclear.

METHODS

We studied 146 457 cases aged 60-99 years in the German federal state of Bavaria who were immunized against COVID-19 and tested positive for it from February 2022 to January 2023. We calculated adjusted hazard ratios for a severe course (hospitalization or death due to COVID-19) for different intervals between the onset of full primary or booster immunity and the date of the infection.

RESULTS

3342 (2.3%) severe courses of COVID-19 were observed in the first 60 days after the infection. The risk of a severe course rose with the interval between the onset of immune protection and the infection (adjusted hazard ratios and 95% confidence intervals at 6, 9, 12, and 15 months: 1.14 [1.08; 1.20]; 1.33 [1.24; 1.42]; 1.39 [1.25; 1.54]; 1.61 [1.35; 1.93]). The risk rose more slowly when mRNA-based vaccines were used exclusively. In a previous study, we observed 82% initial efficacy in cases aged 60 and above who received a booster vaccination (compared to unvaccinated cases) and an absolute risk reduction of 2.1%. If one extrapolates these findings to the current study, the residual efficacy and absolute risk reduction are found to be approximately 71% and 1.8% (respectively) at 6 months, and 32% and 0.8% at 15 months.

CONCLUSION

These results indicate that, during the Omicron wave, the protection of older persons against a severe COVID-19 course gradually declined from six months after vaccination onward. The limitations of this study include confounders that could not be taken into account, possible misclassification of the cause of death, and selection bias due to missing information about vaccination status and severe COVID-19 courses.

Protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant: a systematic review and meta-analysis

OBJECTIVES

The rapid spread of the SARS-CoV-2 Omicron variant has raised concerns regarding waning vaccine-induced immunity and durability. We evaluated protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant and its sublineages.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Electronic databases and other resources (PubMed, Embase, CENTRAL, MEDLINE, CINAHL PLUS, APA PsycINFO, Web of Science, Scopus, ScienceDirect, MedRxiv and bioRxiv) were searched until December 2022.

STUDY ELIGIBILITY CRITERIA

We included studies that assessed the effectiveness of mRNA vaccine booster doses against SARS-CoV-2 infection and severe COVID-19 outcomes caused by the subvariant.

DATA EXTRACTION AND SYNTHESIS

Estimates of vaccine effectiveness (VE) at different time points after the third-dose and fourth-dose vaccination were extracted. Random-effects meta-analysis was used to compare VE of the third dose versus the primary series, no vaccination and the fourth dose at different time points. The certainty of the evidence was assessed by Grading of Recommendations, Assessments, Development and Evaluation approach.

RESULTS

This review included 50 studies. The third-dose VE, compared with the primary series, against SARS-CoV-2 infection was 48.86% (95% CI 44.90% to 52.82%, low certainty) at ≥14 days, and gradually decreased to 38.01% (95% CI 13.90% to 62.13%, very low certainty) at ≥90 days after the third-dose vaccination. The fourth-dose VE peaked at 14-30 days (56.70% (95% CI 50.36% to 63.04%), moderate certainty), then quickly declined at 61-90 days (22% (95% CI 6.40% to 37.60%), low certainty). Compared with no vaccination, the third-dose VE was 75.84% (95% CI 40.56% to 111.12%, low certainty) against BA.1 infection, and 70.41% (95% CI 49.94% to 90.88%, low certainty) against BA.2 infection at ≥7 days after the third-dose vaccination. The third-dose VE against hospitalisation remained stable over time and maintained 79.30% (95% CI 58.65% to 99.94%, moderate certainty) at 91-120 days. The fourth-dose VE up to 60 days was 67.54% (95% CI 59.76% to 75.33%, moderate certainty) for hospitalisation and 77.88% (95% CI 72.55% to 83.21%, moderate certainty) for death.

CONCLUSION

The boosters provided substantial protection against severe COVID-19 outcomes for at least 6 months, although the duration of protection remains uncertain, suggesting the need for a booster dose within 6 months of the third-dose or fourth-dose vaccination. However, the certainty of evidence in our VE estimates varied from very low to moderate, indicating significant heterogeneity among studies that should be considered when interpreting the findings for public health policies.

PROSPERO REGISTRATION NUMBER

CRD42023376698.

Lessons Learned in Elective Surgeries After 6 Pandemic Waves of SARS-CoV-2. A Single European Center Experience

BACKGROUND

The reported high surgical morbidity and mortality in patients with SARS-CoV-2 prompted preoperative screening and modification of surgical protocols. Although vaccination and treatment of COVID-19 have resulted in lower hospitalization rates and infection severity, publications on postoperative results have not been updated. The aim of the study was to analyze the outcomes of patients undergoing surgery in two periods with high incidence of SARS-CoV-2 infection, before and after vaccination.

MATERIALS AND METHODS

This is a prospective cohort study of patients undergoing surgery in two periods: March-June 2020 (Group2020) and December 2021-February 2022 (Group2022) (after massive vaccination).

RESULTS

In total, 618 patients who underwent surgery were included in the analysis (Group2020: 343 vs. Group2022: 275). Significantly more oncological procedures were performed in Group2020, and there were no differences in postoperative complications. Nosocomial SARS-CoV-2 infection occurred in 4 patients in Group2020 and 1 patient in Group2022. In Group 2022, 70 patients (25.4%) had COVID-19 prior to surgery, and 68 (97.1%) were vaccinated. Comparative analysis between patients with past COVID-19 and those without showed no difference in postoperative morbidity and mortality. According to the time elapsed between SARS-CoV-2 infection and surgery (≤ 7 or > 7 weeks), comparative analysis showed no significant differences.

CONCLUSION

The establishment of preoperative screening protocols for SARS-CoV-2 infection results in a low incidence of nosocomial infection and optimal postoperative outcomes. Preoperative SARS-CoV-2 infection in vaccinated patients was not associated with increased postoperative complications, even in shorter periods after infection. In surgical patients, individualized preoperative evaluation after SARS-CoV-2 infection may be more important than strict time limitation.

Comparative effectiveness and duration of protection of ChAdOx1, CoronaVac, BNT162b2, mRNA-1273, and Ad26.COV2.S COVID-19 vaccines for symptomatic and hospitalized Mu, Delta, and Omicron: A test-negative case-control study

OBJECTIVE

We carried out a study to estimate the vaccine effectiveness (VE) of homologous vaccination schedules against COVID-19, using data from mandatory information systems from Bogota, Colombia.

METHODS

A test-negative case-control study in adults from Bogota (Colombia), between March 1st of 2021 and February 25th of 2022. We assess VE among symptomatic COVID-19 cases during the Mul, Delta, and Omicron predominance periods in Bogota, with controls matched by sex, age (±5 years), and date of testing (±7 days), using a case:control ratio of 1:1. We selected homologous vaccination schedules with ChAdOx1, CoronaVac, BNT162b2, mRNA-1273, and Ad26.COV2.S. VE was reported as one minus the odds ratio in adjusted conditional logistic regressions, with their 95% confidence intervals (CI). A p-value < 0.05 was considered statistically significant.

RESULTS

52,913 cases were matched to controls, 16,722 for Mu, 14,094 for Delta, and 22,097 for Omicron. VE was high against COVID-19 during Mu weeks with full vaccination using the monovalent BNT162b2 (VE: 69; 95% CI, 65 to 72) vaccine and ChAdOx1 (VE: 64; 95% CI, 31 to 81) and significantly lower with CoronaVac (P < 0.001) and Ad26.COV2.S (P = 0.005). During Delta, VE against COVID-19 was higher with BNT162b2 (VE: 55; 95% CI, 51 to 58). The VE for COVID-19 cases during Omicron was higher with a booster dose of monovalent BNT162b2 (VE: 45; 95% CI, 34 to 54). The VE of primary series and booster for ChAdOx1, Ad26.COV2.S, and CoronaVac did not show protection for Omicron.

CONCLUSION

Our study provides further evidence on the protective effect of mRNA vaccines for Omicron, and warrant that the duration of protection against symptomatic infection may last for only a few months.

Socioeconomic Differences in SARS-CoV-2 Infection and Vaccination in Germany: A Seroepidemiological Study After One Year of COVID-19 Vaccination Campaign

Objective: To evaluate the socioeconomic patterns of SARS-CoV-2 antigen contacts through infection, vaccination or both ("hybrid immunity") after 1 year of vaccination campaign. Methods: Data were derived from the German seroepidemiological Corona Monitoring Nationwide study (RKI-SOEP-2; n = 10,448; November 2021-February 2022). Combining serological and self-report data, we estimated adjusted prevalence ratios (PR) of SARS-CoV-2 infection, COVID-19 vaccination, basic immunization (at least two SARS-CoV-2 antigen contacts through vaccination and/or infection), and three antigen contacts by education and income. Results: Low-education groups had 1.35-times (95% CI 1.01-1.82) the risk of SARS-CoV-2 infection compared to high-education groups. COVID-19 vaccination (at least one dose) and basic immunization decreased with lower education and income. Low-education and low-income groups were less likely to have had at least three antigen contacts (PR low vs. high education: 0.74, 95% CI 0.65-0.84; PR low vs. high income: 0.66, 95% CI 0.57-0.77). Conclusion: The results suggest a lower level of protection against severe COVID-19 for individuals from low and medium socioeconomic groups. Pandemic response and vaccination campaigns should address the specific needs and barriers of these groups.

COVID-19 Vaccination Effectiveness in the General Population of an Italian Province: Two Years of Follow-Up

We carried out a cohort study on the overall population of the province of Pescara, Italy, to assess the real-world effectiveness of SARS-CoV-2 vaccination against infection, severe, or lethal COVID-19, two years after the start of the vaccination campaign. We included all the resident or domiciled subjects, and extracted the official demographic, vaccination, COVID-19, hospital and co-pay exemption datasets from 1 January 2021, up to 15 February 2023. Cox proportional hazards analyses were adjusted for gender, age, diabetes, hypertension, COPD, major cardio- and cerebrovascular events, cancer, and kidney diseases. Throughout the follow-up (466 days on average), 186,676 subjects received greater than or equal to three vaccine doses (of ChAdOx1 nCoV-19, BNT162b2, mRNA-1273, NVX-CoV2373, or JNJ-78436735), 47,610 two doses, 11,452 one dose, and 44,989 none. Overall, 40.4% of subjects were infected with SARS-CoV-2. Of them, 2.74% had severe or lethal (1.30%) COVID-19. As compared to the unvaccinated, the individuals who received greater than or equal to one booster dose showed a ≥85% lower risk of severe or lethal COVID-19. A massive impact of vaccination was found among the elderly: 22.0% of the unvaccinated, infected individuals died, as opposed to less than 3% of those who received greater than or equal to three vaccine doses. No protection against infection was observed, although this finding was certainly influenced by the Italian restriction policies to control the pandemic. Importantly, during the Omicron predominance period, only the group who received at least a booster dose showed a reduced risk of COVID-19-related death.

Safety and effectiveness of vaccines against COVID-19 in children aged 5-11 years: a systematic review and meta-analysis

BACKGROUND

To date, more than 761 million confirmed SARS-CoV-2 infections have been recorded globally, and more than half of all children are estimated to be seropositive. Despite high SARS-CoV-2 infection incidences, the rate of severe COVID-19 in children is low. We aimed to assess the safety and efficacy or effectiveness of COVID-19 vaccines approved in the EU for children aged 5-11 years.

METHODS

In this systematic review and meta-analysis, we included studies of any design identified through searching the COVID-19 L·OVE (living overview of evidence) platform up to Jan 23, 2023. We included studies with participants aged 5-11 years, with any COVID-19 vaccine approved by the European Medicines Agency-ie, mRNA vaccines BNT162b2 (Pfizer-BioNTech), BNT162b2 Bivalent (against original strain and omicron [BA.4 or BA.5]), mRNA-1273 (Moderna), or mRNA-1273.214 (against original strain and omicron BA.1). Efficacy and effectiveness outcomes were SARS-CoV-2 infection (PCR-confirmed or antigen-test confirmed), symptomatic COVID-19, hospital admission due to COVID-19, COVID-19-related mortality, multisystem inflammatory syndrome in children (MIS-C), and long-term effects of COVID-19 (long COVID or post-COVID-19 condition as defined by study investigators or per WHO definition). Safety outcomes of interest were serious adverse events, adverse events of special interest (eg, myocarditis), solicited local and systemic events, and unsolicited adverse events. We assessed risk of bias and rated the certainty of evidence (CoE) using the Grading of Recommendations Assessment, Development and Evaluation approach. This study was prospectively registered with PROSPERO, CRD42022306822.

FINDINGS

Of 5272 screened records, we included 51 (1·0%) studies (n=17 [33%] in quantitative synthesis). Vaccine effectiveness after two doses against omicron infections was 41·6% (95% CI 28·1-52·6; eight non-randomised studies of interventions [NRSIs]; CoE low), 36·2% (21·5-48·2; six NRSIs; CoE low) against symptomatic COVID-19, 75·3% (68·0-81·0; six NRSIs; CoE moderate) against COVID-19-related hospitalisations, and 78% (48-90, one NRSI; CoE very low) against MIS-C. Vaccine effectiveness against COVID-19-related mortality was not estimable. Crude event rates for deaths in unvaccinated children were less than one case per 100 000 children, and no events were reported for vaccinated children (four NRSIs; CoE low). No study on vaccine effectiveness against long-term effects was identified. Vaccine effectiveness after three doses was 55% (50-60; one NRSI; CoE moderate) against omicron infections, and 61% (55-67; one NRSI; CoE moderate) against symptomatic COVID-19. No study reported vaccine efficacy or effectiveness against hospitalisation following a third dose. Safety data suggested no increased risk of serious adverse events (risk ratio [RR] 0·83 [95% CI 0·21-3·33]; two randomised controlled trials; CoE low), with approximately 0·23-1·2 events per 100 000 administered vaccines reported in real-life observations. Evidence on the risk of myocarditis was uncertain (RR 4·6 [0·1-156·1]; one NRSI; CoE low), with 0·13-1·04 observed events per 100 000 administered vaccines. The risk of solicited local reactions was 2·07 (1·80-2·39; two RCTs; CoE moderate) after one dose and 2·06 (1·70-2·49; two RCTs; CoE moderate) after two doses. The risk of solicited systemic reactions was 1·09 (1·04-1·16; two RCTs; CoE moderate) after one dose and 1·49 (1·34-1·65; two RCTs; CoE moderate) after two doses. The risk of unsolicited adverse events after two doses (RR 1·21 [1·07-1·38]; CoE moderate) was higher among mRNA-vaccinated compared with unvaccinated children.

INTERPRETATION

In children aged 5-11 years, mRNA vaccines are moderately effective against infections with the omicron variant, but probably protect well against COVID-19 hospitalisations. Vaccines were reactogenic but probably safe. Findings of this systematic review can serve as a basis for public health policy and individual decision making on COVID-19 vaccination in children aged 5-11 years.

FUNDING

German Federal Joint Committee.

Clinical Characteristics of Mild Patients with Breakthrough Infection of Omicron Variant in China after Relaxing the Dynamic Zero COVID-19 Policy

For SARS-CoV-2 mutants, the effectiveness of the COVID-19 vaccines is still controversial. In this study, we aimed to investigate the clinical characteristics of Omicron-infected patients who completed primary immunization and booster immunization, respectively, during the rapid propagation of the Omicron variant in China. A total of 932 patients with confirmed SARS-CoV-2 infection from 18 December 2022 to 1 January 2023 were included in this survey by filling out questionnaires online. The enrolled patients were divided into the primary immunization group and the booster immunization group according to their vaccination status. During the whole course of disease, the most frequent symptoms were fever (90.6%), cough (84.3%), weakness (77.4%), headache and dizziness (76.1%), and myalgia (73.9%). Nearly 90% of the patients had symptoms lasting for less than 10 days, and 39.8% of the patients ended the course of the disease in 4-6 days. A total of 58.8% of these patients had a fever with a maximum body temperature of over 38.5 °C. Moreover, 61.4% of the patients had a fever that lasted less than 2 days. There were no obvious differences in initial symptoms, cardinal symptoms, symptom duration time, maximum body temperature, and fever duration time between the two groups of patients. In addition, no significant difference was found in the positive or negative conversion time of SARS-CoV-2 antigen/nucleic acid between the two groups of patients. For mild patients with Omicron breakthrough infection, enhanced immunization has no significant impact on the clinical performance and duration of viral infection compared with primary immunization. The reasons behind the different clinical manifestations of patients with mild symptoms after the breakthrough infection of the Omicron strain are still worth further research. Heterologous vaccination may be a better strategy for enhanced immunization, which can help improve the immune protection ability of the population. Further research should be carried out on vaccines against mutant strains and spectral anti-COVID-19 vaccines.

Effectiveness, Immunogenicity and Harms of Additional SARS-CoV-2 Vaccine Doses in Kidney Transplant Recipients: A Systematic Review

BACKGROUND

Kidney transplant recipients (KTRs) who have a highly impaired immune response are in need of intensified and safe vaccination strategies to achieve seroconversion and prevent severe disease.

METHODS

We searched the Web of Science Core Collection, the Cochrane COVID-19 Study Register and the WHO COVID-19 global literature on coronavirus disease from January 2020 to 22 July 2022 for prospective studies that assessed immunogenicity and efficacy after three or more SARS-CoV-2 vaccine doses.

RESULTS

In 37 studies on 3429 patients, de novo seroconversion after three and four vaccine doses ranged from 32 to 60% and 25 to 37%. Variant-specific neutralization was 59 to 70% for Delta and 12 to 52% for Omicron. Severe disease after infection was rarely reported but all concerned KTRs lacked immune responses after vaccination. Studies investigating the clinical course of COVID-19 found remarkably higher rates of severe disease than in the general population. Serious adverse events and acute graft rejections were very rare. Substantial heterogeneity between the studies limited their comparability and summary.

CONCLUSION

Additional SARS-CoV-2 vaccine doses are potent and safe in general terms as well as regarding transplant-specific outcomes whilst the Omicron wave remains a significant threat to KTRs without adequate immune responses.

Insights for COVID-19 in 2023

Predictions for a near end of the pandemic by the World Health Organization should be interpreted with caution. Current evidence indicates that the efficacy of a fourth dose of classical mRNA vaccines (BT162b2 or mRNA-1273) is low and short-lived in preventing SARS-CoV-2 infection in its predominant variant (Omicron). However, its efficacy is high against severe symptomatic infection, hospitalization and death. The new vaccines being introduced are bivalent and active against the Omicron variants. Potential new vaccines to be introduced in the coming year include a vaccine based on a recombinant protein that emulates the receptor binding domain of the Spike protein under development by the Spanish company Hipra, as well as vaccines for nasal or oral administration. Available information suggests that vaccines against COVID-19 can be administered in association with influenza vaccination without particular complications. New drugs against COVID-19, both antiviral and anti-inflammatory, are under investigation, but this does not seem to be the case with monoclonal antibodies. The indication to use masks in some circumstances will be maintained next year in view of the accumulation of scientific data on their efficacy. Finally, the long COVID or Post-COVID syndrome may continue to affect a very high proportion of patients who have had the disease, requiring combined diagnostic and therapeutic resources.

Assessing COVID-19 vaccine effectiveness against Omicron subvariants: Report from a meeting of the World Health Organization

Emerging in November 2021, the SARS-CoV-2 Omicron variant of concern exhibited marked immune evasion resulting in reduced vaccine effectiveness against SARS-CoV-2 infection and symptomatic disease. Most vaccine effectiveness data on Omicron are derived from the first Omicron subvariant, BA.1, which caused large waves of infection in many parts of the world within a short period of time. BA.1, however, was replaced by BA.2 within months, and later by BA.4 and BA.5 (BA.4/5). These later Omicron subvariants exhibited additional mutations in the spike protein of the virus, leading to speculation that they might result in even lower vaccine effectiveness. To address this question, the World Health Organization hosted a virtual meeting on December 6, 2022, to review available evidence for vaccine effectiveness against the major Omicron subvariants up to that date. Data were presented from South Africa, the United Kingdom, the United States, and Canada, as well as the results of a review and meta-regression of studies that evaluated the duration of the vaccine effectiveness for multiple Omicron subvariants. Despite heterogeneity of results and wide confidence intervals in some studies, the majority of studies showed vaccine effectiveness tended to be lower against BA.2 and especially against BA.4/5, compared to BA.1, with perhaps faster waning against severe disease caused by BA.4/5 after a booster dose. The interpretation of these results was discussed and both immunological factors (i.e., more immune escape with BA.4/5) and methodological issues (e.g., biases related to differences in the timing of subvariant circulation) were possible explanations for the findings. COVID-19 vaccines still provide some protection against infection and symptomatic disease from all Omicron subvariants for at least several months, with greater and more durable protection against severe disease.

Dynamics of Antibody Responses after Asymptomatic and Mild to Moderate SARS-CoV-2 Infections: Real-World Data in a Resource-Limited Country

The dynamics of humoral immune responses of patients after SARS-CoV-2 infection is unclear. This study prospectively observed changes in anti-receptor binding domain immunoglobulin G (anti-RBD IgG) and neutralizing antibodies against the Wuhan and Delta strains at 1, 3, and 6 months postinfection between October 2021 and May 2022. Demographic data, clinical characteristics, baseline parameters, and blood samples of participants were collected. Of 5059 SARS-CoV-2 infected adult patients, only 600 underwent assessment at least once between 3 and 6 months after symptom onset. Patients were categorized as immunocompetent (n = 566), immunocompromised (n = 14), or reinfected (n = 20). A booster dose of a COVID-19 vaccine was strongly associated with maintained or increased COVID-19 antibody levels. The booster dose was also more strongly associated with antibody responses than the primary vaccination series. Among patients receiving a booster dose of a mRNA vaccine or a heterologous regimen, antibody levels remained steady or even increased for 3 to 6 months after symptom onset compared with inactivated or viral vector vaccines. There was a strong correlation between anti-RBD IgG and neutralizing antibodies against the Delta variant. This study is relevant to resource-limited countries for administering COVID-19 vaccines 3 to 6 months after infection.

Vaccine effectiveness against severe COVID-19 during the Omicron wave in Germany: results from the COViK study

PURPOSE

COViK, a prospective hospital-based multicenter case-control study in Germany, aims to assess the effectiveness of COVID-19 vaccines against severe disease. Here, we report vaccine effectiveness (VE) against COVID-19-caused hospitalization and intensive care treatment during the Omicron wave.

METHODS

We analyzed data from 276 cases with COVID-19 and 494 control patients recruited in 13 hospitals from 1 December 2021 to 5 September 2022. We calculated crude and confounder-adjusted VE estimates.

RESULTS

21% of cases (57/276) were not vaccinated, compared to 5% of controls (26/494; p < 0.001). Confounder-adjusted VE against COVID-19-caused hospitalization was 55.4% (95% CI: 12-78%), 81.5% (95% CI: 68-90%) and 95.6% (95%CI: 88-99%) after two, three and four vaccine doses, respectively. VE against hospitalization due to COVID-19 remained stable up to one year after three vaccine doses.

CONCLUSION

Three vaccine doses remained highly effective in preventing severe disease and this protection was sustained; a fourth dose further increased protection.

Immune correlates analysis of a phase 3 trial of the AZD1222 (ChAdOx1 nCoV-19) vaccine

In the phase 3 trial of the AZD1222 (ChAdOx1 nCoV-19) vaccine conducted in the U.S., Chile, and Peru, anti-spike binding IgG concentration (spike IgG) and pseudovirus 50% neutralizing antibody titer (nAb ID50) measured four weeks after two doses were assessed as correlates of risk and protection against PCR-confirmed symptomatic SARS-CoV-2 infection (COVID-19). These analyses of SARS-CoV-2 negative participants were based on case-cohort sampling of vaccine recipients (33 COVID-19 cases by 4 months post dose two, 463 non-cases). The adjusted hazard ratio of COVID-19 was 0.32 (95% CI: 0.14, 0.76) per 10-fold increase in spike IgG concentration and 0.28 (0.10, 0.77) per 10-fold increase in nAb ID50 titer. At nAb ID50 below the limit of detection (< 2.612 IU50/ml), 10, 100, and 270 IU50/ml, vaccine efficacy was -5.8% (-651%, 75.6%), 64.9% (56.4%, 86.9%), 90.0% (55.8%, 97.6%) and 94.2% (69.4%, 99.1%). These findings provide further evidence towards defining an immune marker correlate of protection to help guide regulatory/approval decisions for COVID-19 vaccines.

Vaccine-induced or hybrid immunity and COVID-19-associated mortality during the Omicron wave

BACKGROUND

It is not yet entirely clear to what extent vaccine-induced or hybrid immunity protects individuals in Germany from death during the omicron wave of the COVID-19 pandemic.

METHODS

In this retrospective study, we evaluated 470 159 cases over age 59 in the German federal state of Bavaria who tested positive for SARS-CoV-2 between 1 January and 30 June 2022. Cox models were used to estimate adjusted hazard ratios (aHR) for dying within 60 days of the infection, depending on sex, age, time point of infection, and a range of immunity levels.

RESULTS

Over the period of observation, 3836 COVID-19-associated deaths were registered (case fatality rate 0.82 %). Risk of death was significantly lower in cases with a higher immunity level than in unvaccinated cases (aHR for a full primary immunity level, if reached less than six months before the time of the infection: 0.30, 95 %-confidence interval [0.23; 0.39]; if reached more than six months before: aHR 0.46 [0.35; 0.60]). A boosted immunity level lowered risk of death even further (if reached less than three months before the infection: aHR 0.17 [0.15; 0.20]; if reached more than three months before: aHR 0.25 [0.21; 0.29]).

CONCLUSION

Among elderly persons in Bavaria, a higher immunity level was associated with a substantial degree of protection against death during the Omicron wave; the strength of protection may have diminished somewhat over time.

SARS-CoV-2 in animals: susceptibility of animal species, risk for animal and public health, monitoring, prevention and control

The epidemiological situation of SARS-CoV-2 in humans and animals is continually evolving. To date, animal species known to transmit SARS-CoV-2 are American mink, raccoon dog, cat, ferret, hamster, house mouse, Egyptian fruit bat, deer mouse and white-tailed deer. Among farmed animals, American mink have the highest likelihood to become infected from humans or animals and further transmit SARS-CoV-2. In the EU, 44 outbreaks were reported in 2021 in mink farms in seven MSs, while only six in 2022 in two MSs, thus representing a decreasing trend. The introduction of SARS-CoV-2 into mink farms is usually via infected humans; this can be controlled by systematically testing people entering farms and adequate biosecurity. The current most appropriate monitoring approach for mink is the outbreak confirmation based on suspicion, testing dead or clinically sick animals in case of increased mortality or positive farm personnel and the genomic surveillance of virus variants. The genomic analysis of SARS-CoV-2 showed mink-specific clusters with a potential to spill back into the human population. Among companion animals, cats, ferrets and hamsters are those at highest risk of SARS-CoV-2 infection, which most likely originates from an infected human, and which has no or very low impact on virus circulation in the human population. Among wild animals (including zoo animals), mostly carnivores, great apes and white-tailed deer have been reported to be naturally infected by SARS-CoV-2. In the EU, no cases of infected wildlife have been reported so far. Proper disposal of human waste is advised to reduce the risks of spill-over of SARS-CoV-2 to wildlife. Furthermore, contact with wildlife, especially if sick or dead, should be minimised. No specific monitoring for wildlife is recommended apart from testing hunter-harvested animals with clinical signs or found-dead. Bats should be monitored as a natural host of many coronaviruses.

A Systematic Review and Meta-Analysis on the Real-World Effectiveness of COVID-19 Vaccines against Infection, Symptomatic and Severe COVID-19 Disease Caused by the Omicron Variant (B.1.1.529)

Real-world data on the effectiveness of COVID-19 vaccines against the Omicron variant (B.1.1.529) is limited. This systematic review aimed to investigate the real-world effectiveness and durability of protection conferred by primary course and booster vaccines against confirmed Omicron infection, and severe outcomes. We systematically searched literature up to 1 August 2022. Meta-analysis was performed with the DerSimonian-Laird random-effects model to estimate the pooled vaccine effectiveness (VE). Overall, 28 studies were included representing 11 million individuals. The pooled VE against Omicron infection was 20.4% (95%CI: 12.1-28.7%) and 23.4% (95%CI: 13.5-33.3%) against symptomatic infection with variation based on vaccine type and age groups. VE sharply declined from 28.1% (95%CI: 19.1-37.1%) at three months to 3.9% (95%CI: -24.8-32.7%) at six months. Similar trends were observed for symptomatic Omicron infection. A booster dose restored protection against Omicron infection up to 51.1% (95%CI: 43.8-58.3%) and 57.3% (95%CI: 54.0-60.5%) against symptomatic infection within three months; however, this waned to 32.8% (95%CI: 16.8-48.7%) within six months. VE against severe Omicron infection following the primary course was 63.6% (95%CI: 57.5-69.7%) at three months, decreased to 49% (95%CI: 35.7-63.4%) within six months, and increased to 86% after the first or second booster dose.

Non-specific prevention of COVID-19 during vaccination against a new coronavirus infection: results of a multicenter, double-blind, placebo-controlled, randomized clinical trial

Background. A multicenter, double-blind, placebo-controlled, randomized clinical trial (RCT) of the phase III efficacy and safety of Ergoferon for the non-specific prevention of COVID-19 during vaccination against a new coronavirus infection was conducted (permission of the Ministry of Health of the Russian Federation №559 dated 22.09.2021; ClinicalTrials.gov Identifier: NCT05069649). Aim. To evaluate the efficacy and safety of the use of Ergoferon for the non-specific prevention of COVID-19 during vaccination against a new coronavirus infection. Materials and methods. From October 2021 to April 2022, 1,057 patients aged 18 to 92 years who received component I of the Gam-COVID-Vac vaccine were included. After screening, 1,050 patients were randomized into 2 groups: 526 people received Ergoferon according to the prophylactic scheme 1 tablet per administration 2 times a day for 3 weeks, the drug is not allowed during the meal and should be kept in the mouth without swallowing, until completely dissolved; 524 patients received a placebo according to the Ergoferon scheme. The total duration of participation in the study was 5 weeks + 3 days. The primary endpoint is the number of RT-PCR confirmed cases of SARS-CoV-2 infection, regardless of the presence of symptoms during participation in the study. An additional criterion of effectiveness is the proportion of those hospitalized with COVID-19. The safety assessment included consideration of the presence and nature of adverse events (AEs), their severity, relationship with the drug intake, and outcome. Statistical data processing was carried out using SAS 9.4 with the calculation of the exact Fisher test, 2 test, CochraneMantelHensel test, Wilcoxon test and other parameters. Results. The ITT (Intention-to-treat) and PP [Per Protocol] efficacy analysis included data from 1,050 [970] patients: 526 [489] people Ergoferon group and 524 [481] people Placebo group. The primary endpoint the number of laboratory-confirmed cases of SARS-CoV-2 infections was 3 times less compared to placebo 7 (1.43%) vs 22 (4.57%), respectively (p=0.0046; [p=0.0041]). Taking Ergoferon reduces the risk of SARS-CoV-2 infection by more than 3 times in vaccinated patients during 5 weeks of the vaccination and post-vaccination periods (p=0.0046 [p=0.0041]). Of the COVID-19 patients in the Ergoferon group (1.33%) nobody was hospitalized. According to the Post hoc analysis, Ergoferon reduces the risk of COVID-19 disease by 4 times in the period between the components I and II of the Gam-COVID-Vac vaccine (p=0.0066 [p=0.006]). The frequency of AEs in both groups did not differ. There were no registered AEs associated with the drug with a reliable degree. There was a high level of patient compliance and good tolerability. Conclusion. Ergoferon is an effective and safe drug for the prevention of COVID-19 in people vaccinated against a new coronavirus infection.

Comparison of Long COVID-19 Caused by Different SARS-CoV-2 Strains: A Systematic Review and Meta-Analysis

Although many studies of long COVID-19 were reported, there was a lack of systematic research which assessed the differences of long COVID-19 in regard to what unique SARS-CoV-2 strains caused it. As such, this systematic review and meta-analysis aims to evaluate the characteristics of long COVID-19 that is caused by different SARS-CoV-2 strains. We systematically searched the PubMed, EMBASE, and ScienceDirect databases in order to find cohort studies of long COVID-19 as defined by the WHO (Geneva, Switzerland). The main outcomes were in determining the percentages of long COVID-19 among patients who were infected with different SARS-CoV-2 strains. Further, this study was registered in PROSPERO (CRD42022339964). A total of 51 studies with 33,573 patients was included, of which three studies possessed the Alpha and Delta variants, and five studies possessed the Omicron variant. The highest pooled estimate of long COVID-19 was found in the CT abnormalities (60.5%; 95% CI: 40.4%, 80.6%) for the wild-type strain; fatigue (66.1%; 95% CI: 42.2%, 89.9%) for the Alpha variant; and ≥1 general symptoms (28.4%; 95% CI: 7.9%, 49.0%) for the Omicron variant. The pooled estimates of ≥1 general symptoms (65.8%; 95% CI: 47.7%, 83.9%) and fatigue were the highest symptoms found among patients infected with the Alpha variant, followed by the wild-type strain, and then the Omicron variant. The pooled estimate of myalgia was highest among patients infected with the Omicron variant (11.7%; 95%: 8.3%, 15.1%), compared with those infected with the wild-type strain (9.4%; 95%: 6.3%, 12.5%). The pooled estimate of sleep difficulty was lowest among the patients infected with the Delta variant (2.5%; 95%: 0.2%, 4.9%) when compared with those infected with the wild-type strain (24.5%; 95%: 17.5%, 31.5%) and the Omicron variant (18.7%; 95%: 1.0%, 36.5%). The findings of this study suggest that there is no significant difference between long COVID-19 that has been caused by different strains, except in certain general symptoms (i.e., in the Alpha or Omicron variant) and in sleep difficulty (i.e., the wild-type strain). In the context of the ongoing COVID-19 pandemic and its emerging variants, directing more attention to long COVID-19 that is caused by unique strains, as well as implementing targeted intervention measures to address it are vital.

Evaluation der COVID-19-Impfung nach breiter Anwendung – ein Zwischenfazit für Deutschland im Juli 2022

Seit Dezember 2020 stehen in Deutschland Impfstoffe gegen COVID-19 zur Verfügung. Zu den Hauptaufgaben des Fachgebiets Impfprävention des Robert Koch-Instituts (RKI) in der COVID-19-Pandemie gehören die Erhebung von Impfquoten und das Monitoring der Wirksamkeit der Impfung. Der Artikel gibt einen Überblick über die hierfür während der Pandemie etablierten Strukturen, Datengrundlagen und Studien. Ausgehend vom Digitalen Impfquotenmonitoring (DIM), welches für die tagesaktuelle Berechnung der Impfquote in mehreren Altersgruppen verwendet wird, werden die Berechnung der Inzidenzen nach Impfstatus und die Methodik der Impfeffektivitätsschätzung gegen verschiedene Endpunkte (Hospitalisierung, intensivstationäre Betreuung, Tod) beschrieben. Während diese Methode lediglich eine erste Abschätzung der Impfeffektivität erlaubt, kann in bevölkerungsbezogenen nichtrandomisierten Studien eine detailliertere und genauere Untersuchung der Wirksamkeit der COVID-19-Impfstoffe unter Realbedingungen erfolgen. Hierzu wird die gemeinsam mit dem Paul-Ehrlich-Institut (PEI) durchgeführte krankenhausbasierte Fall-Kontrollstudie COViK vorgestellt. Die Vorteile und Limitationen der genannten Strukturen und Instrumente werden diskutiert. Abschließend wird ein Ausblick auf hieraus resultierende künftige Herausforderungen in der Pandemie und beim Übergang in die endemische Lage gegeben.