Immunogenicity and reactogenicity of SARS-CoV-2 vaccines BNT162b2 and CoronaVac in healthy adolescents

Optimization of hypo-alloimmunogenic multispecific CAR-T and SARS-CoV-2-specific T cells for off-the-shelf adoptive cell therapy

Despite promising results with chimeric antigen receptor modified T(CAR-T) cells and virus-specific T(VST) cells, both forms of therapy are limited by timely availability, affordability, in vivo persistency, and antigen escape. To overcome these barriers, we developed multitargeting hypo-alloimmunogenic CAR-T and VST for off-the-shelf administration. We generated bi-specific CAR-T against CD19 and CD22 and tri-specific VST against S, M, and N proteins of SARS-CoV-2 for real patient use. Portions of these clinical-grade products were collected for proof-of-concept laboratory studies mimicking off-the-shelf settings. By electroporation delivery of Cas9 nuclease/guide RNA (gRNA) ribonucleoprotein, we developed a single-step approach to knockout B2M, achieving efficient (>80% of cells) B2M null on both bi-specific CAR-T and tri-specific VST, leading to marked reduction of allo-immunogenicity with intact potency, antigen specificity, phenotypes, and proliferative potential. Using newly designed paired Cas9 nickases-AAV6 B2M site-specific knockin system, we further refined the approach to re-express HLA-E in B2M null bi-specific CAR-T cells (>50% of cells), offering protection from natural killer cytotoxicity. The editing was highly specific with minimal off-target effects. Our approach enables expedient production of clinical-grade, off-the-shelf, hypo-alloimmunogenic, multi-specific CAR-T and VST, with improved potential for long-term in vivo persistence, primary disease control, genome-safety, immediate availability, product homogeneity, and reduced cost.

The Overlooked Nucleocapsid Response: A Cohort Study of SARS-CoV-2 Vaccines in Brazil

SARS-CoV-2 has caused global disruptions, prompting studies on immune responses to COVID-19 vaccines, particularly antibodies against the Spike (S) protein. However, responses to the Nucleocapsid (N) protein remain less explored. This study evaluated whether CoronaVac induces anti-N antibodies, and analyzed antibody dynamics after a BNT162b2 booster, given that CoronaVac targets both S and N proteins, while BNT162b2 targets only the S protein. Serum samples were collected at multiple intervals post-vaccination. The percentage of participants with positive anti-N antibodies increased from 40.26% to 62.09% after two doses of CoronaVac, but declined over time, reaching 29.07% and 18.87% after the second and third doses, respectively. However, seropositivity rose to 43.48% three months after the booster. Anti-S antibody levels peaked at 31,394 AU/mL after the booster, compared to 723.4 AU/mL after the first dose. These findings indicate that CoronaVac stimulates antibody responses against both S and N proteins. Monitoring antibody dynamics is crucial for optimizing vaccination strategies, particularly for high-risk populations, to help control COVID-19.

Humoral and cellular immunogenicity of a fourth dose BNT162b2 in children with chronic kidney diseases

Background

Children with chronic kidney disease (CKD) are at risk of severe complications after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and are recommended to receive vaccine boosters. Although coronavirus disease 2019 (COVID-19) boosters are effective in providing immune responses among healthy children, data on the use of a fourth dose among children with CKD are limited.

Methods

We prospectively investigated the immunogenicity and safety of a fourth dose of BNT162b2 in children with CKD. Dosages were 0.1 mL and 0.3 mL for children aged 5-11 years and 11-18 years, respectively. Humoral and cellular immunogenicity was assessed at pre-dose 4, and at 1 and 6 months post-dose 4.

Results

Twenty-one children, with a median age of 14.0 years, were included for evaluation. A fourth dose of BNT162b2 elicited significant increases in humoral spike receptor-binding domain immunoglobulin G levels and T-cell responses. Antibody responses were significantly lower among kidney transplant recipients or children receiving calcineurin inhibitors than other CKD children at 1 month post-dose 4. Breakthrough COVID-19 occurred in three children after the fourth dose, and one was hospitalized. One child developed mild gross hematuria 1 day after the fourth dose, which spontaneously resolved. The overall safety profile was acceptable.

Conclusions

A fourth dose of BNT162b2 was immunogenic and safe in children with CKD.

WITHDRAWN: SA55 broadly neutralizes SARS-CoV-2 and robustly prevents viral escape by JN.1 sublineages

The authors have withdrawn this manuscript because of a conflict of interest. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

Serological insights from SARS-CoV-2 heterologous prime and boost responses in Thailand

During the COVID-19 pandemic, heterologous vaccination strategies were employed to alleviate the strain on vaccine supplies. The Thailand Ministry of Health adopted these strategies using vector, inactivated, and mRNA vaccines. However, this approach has introduced challenges for SARS-CoV-2 sero-epidemiology studies. Our study analysed 647 samples from healthcare workers who received CoronaVac, ChAdOx1 nCoV-19, and BNT162b2 vaccines. The serological profile encompassed responses to various SARS-CoV-2 variants and vectors, measuring IgG, IgM, and IgA isotypes, alongside IgG avidity assays. The results demonstrated that heterologous CoronaVac/ChAdOx1 nCoV-19 schedules elicited significantly stronger antibody responses compared to homologous schedules (IgG: 1.2-fold, IgM: 10.9-fold, IgA: 3.1-fold increase). Additionally, a heterologous BNT162b2 boost at 4-weeks post-initial vaccination showed greater antibody levels than a ChAdOx1 nCoV-19 boost (IgG: 1.1-fold, IgM: slight decrease, IgA: 1.5-fold increase). Using a combination of three analytes, IgG against wild-type Spike trimer, nucleoprotein and Omicron receptor binding domains, enabled the clustering of responses within a statistical Gaussian mixture model that successfully discriminates between breakthrough infections and vaccination types (F-score = 0.82). The development of statistical models to predict breakthrough infections can improve serological surveillance. Overall, our study underscores the necessity for vaccine (re-)development and the creation of serological tools to monitor vaccine performance.

Humoral and cellular immune response to AZD1222 /Covishield and BV152/Covaxin COVID-19 vaccines among adults in India

Several COVID-19 vaccines were developed using different approaches to prevent both symptomatic COVID-19 cases and fatalities. The adults were vaccinated with two doses of AZD1222/Covishield (n = 77) [manufactured by Serum Institute of India Pvt Ltd] vaccine and BV152/Covaxin (n = 99) [manufactured by Bharat Biotech] vaccine. They were assessed for immune response at pre-vaccination, 1 month post first and 6 months post second dose for anti-SARS-CoV-2 IgG antibody, surrogate neutralizing antibody (NAbs), immune phenotypes, antigen specific NK, B and T cell response, their effector functionality by ELISPOT and plasma cytokine profile. Both vaccines elicited enhanced IgG antibody and Nab levels compared to the baseline. BV152/Covaxin, the whole virus inactivated vaccine exhibited higher IgG (70% vs 100%), Nab (90% vs 100%), and robust T cell (31% vs 96%) responses at 6 months post second dose compared to 1 month post first dose justifying the utility of the second dose. Detection of SARS-CoV-2 WV and S1 specific CD4+ central T cell memory response in AZD1222/Covishield vaccinee at 6 months post second dose and higher CD4+ and CD8+ naïve and central memory T cell response in BV152/Covaxin vaccinee at 1 month post first dose indicated the involvement of memory T cells. Persistent IgG and NAb responses along with IgG+B and IgG+memory B cells in AZD1222/Covishield recipients at 6 months post second dose indicated sustained immune memory response. Continued heightened IFN-γ secreting T cell response (ELISPOT) displayed by both the vaccine platforms could serve as a co correlate of protection, further to evaluation in follow up studies. Overall, our data suggest that coordinated functions of humoral and cellular branches of adaptive immunity may pave ways toward protective immunity against COVID-19.

Medium-term immunogenicity of three doses of BNT162b2 and CoronaVac in Hong Kong neuromuscular disease patients

The durability of the immunogenicity elicited by three doses of mRNA-based BNT162b2 and whole-virus inactivated CoronaVac in patients with neuromuscular diseases, particularly those on immunosuppressive drugs and variants of concern, has not been well-established. Our goal was to evaluate medium-term humoral immunogenicity outcomes after 3 doses of these vaccines. Peripheral blood samples were collected from participants 14-49 days and 155-210 days after administration of the third vaccine dose to assess humoral immune responses through serological assays. The immunogenicity outcomes of each patient were compared to those of three age-matched healthy control participants, ensuring a balanced comparison. Both patients that received 3 doses of BNT162b2 and 10 (90.9%) patients that received CoronaVac seroconverted against wild-type-SARS-CoV-2 virus, showing comparable antibody responses to healthy participants. After 6 months, one patient in BNT162b2 and all four patients in CoronaVac groups maintained seropositivity. The JN-1 specific binding antibody response was lower compared to wild-type virus. The use of corticosteroids did not affect seroconversion rate against wild-type virus or JN.1 variant. BNT162b2 and CoronaVac were immunogenic for neuromuscular diseases patients, maintaining durability after 6 months even for those on corticosteroids. Our data support a rapid immunization series utilizing mRNA-based and whole-virus inactivated vaccines for future pandemic.

Booster Vaccination with BNT162b2 Improves Cellular and Humoral Immune Response in the Pediatric Population Immunized with CoronaVac

The SARS-CoV-2 Omicron variant and its sublineages continue to cause COVID-19-associated pediatric hospitalizations, severe disease, and death globally. BNT162b2 and CoronaVac are the main vaccines used in Chile. Much less is known about the Wuhan-Hu-1 strain-based vaccines in the pediatric population compared to adults. Given the worldwide need for booster vaccinations to stimulate the immune response against new Omicron variants of SARS-CoV-2, we characterized the humoral and cellular immune response against Omicron variant BA.1 in a pediatric cohort aged 10 to 16 years who received heterologous vaccination based on two doses of CoronaVac, two doses of CoronaVac (2x) plus one booster dose of BNT162b2 [CoronaVac(2x) + BNT162b2 (1x)], two doses of CoronaVac plus two booster doses of BNT162b2 [CoronaVac(2x) + BNT162b2 (2x)], and three doses of BNT162b2. We observed that the [CoronaVac(2x) + BNT162b2 (2x)] vaccination showed higher anti-S1 and neutralizing antibody titers and CD4 and CD8 T cell immunity specific to the Omicron variant compared to immunization with two doses of CoronaVac alone. Furthermore, from all groups tested, immunity against Omicron was highest in individuals who received three doses of BNT162b2. We conclude that booster vaccination with BNT162b2, compared to two doses of CoronaVac alone, induces a greater protective immunity.

Safety, Immunogenicity, and Effectiveness of Chinese-Made COVID-19 Vaccines in the Real World: An Interim Report of a Living Systematic Review

Background: Several COVID-19 vaccines were developed and approved in China. Of these, the BIBB-CorV and CoronaVac inactivated whole-virion vaccines were widely distributed in China and developing countries. However, the performance of the two vaccines in the real world has not been summarized. Methods: A living systematic review based on findings from ongoing post-licensure studies was conducted, applying standardized algorithms. Articles published between 1 May 2020 and 31 May 2022 in English and Chinese were searched for in Medline, Embase, WanFang Data, medRxiv, bioRxiv, arXiv, SSRN, and Research Square, using SARS-CoV-2, COVID-19, and vaccine as the MeSH terms. Studies with estimates of safety, immunogenicity, and effectiveness from receiving the BIBB-CorV or CoronaVac vaccine that met the predefined screening criteria underwent a full-text review. The Joanna Briggs Institute's Critical Appraisal Checklist and the Cochrane risk of bias were used for assessment of the quality. A random-effects meta-regression model was applied to identify the potential impact factors on the vaccines' effectiveness. Results: In total, 32578 articles were identified, of these, 770 studies underwent a full-text review. Eventually, 213 studies were included. The pooled occurrence of solicited and unsolicited adverse events after any dose of either vaccine varied between 10% and 40%. The top five commonly reported rare adverse events were immunization stress-related responses (211 cases, 50.0%), cutaneous responses (43 cases, 10.2%), acute neurological syndrome (39 cases, 9.2%), anaphylaxis (17 cases, 4.0%), and acute stroke (16 cases, 3.8%). The majority (83.3%) recovered or were relieved within several days. The peak neutralization titers against the ancestral strain was found within 1 month after the completion of the primary series of either vaccine, with a GMT (geometric mean titer) of 43.7 (95% CI: 23.2-82.4), followed by a dramatic decrease within 3 months. At Month 12, the GMT was 4.1 (95% CI: 3.8-4.4). Homologous boosting could restore humoral immunity, while heterologous boosting elicited around sixfold higher neutralization titers in comparison with homologous boosting. The effectiveness of receiving either vaccine against death and severe disease was around 85% for both shortly after the primary series. At Month 12, the protection against death did not decline, while the protection against severe disease decreased to ~75%. Conclusions: Both the BIBP-CorV and CoronaVac inactivated vaccines are safe. Sustained vaccine effectiveness against death was determined 12 months after the primary series, although protection against severe disease decreased slightly over time. A booster dose could strengthen the waning effectiveness; however, the duration of the incremental effectiveness and the additional benefit provided by a heterologous booster need to be studied.

Live virus neutralizing antibodies against pre and post Omicron strains in food and retail workers in Québec, Canada

Background

Measuring the ability of SARS-CoV-2 antibodies to neutralize live viruses remains an effective approach to quantify the level of protection of individuals. We assessed the neutralization activity against the ancestral SARS-CoV-2, Delta, Omicron BA.1, BA.2, BA.2.12.1, BA.4 and BA.5 strains, in 280 vaccinated restaurant/bar, grocery and hardware store workers in Québec, Canada.

Methods

Participants were recruited during the emergence of Omicron BA.1 variant. The neutralizing activity of participant sera was assessed by microneutralization assay.

Results

Serum neutralizing antibody (NtAb) titers of all participants against the ancestral SARS-CoV-2 strain were comparable with those against Delta variant (ranges of titers 10-2032 and 10-2560, respectively), however, their response was significantly reduced against Omicron BA.1, BA2, BA.2.12.1, BA.4 and BA.5 (10-1016, 10-1016, 10-320, 10-80 and 10-254, respectively). Individuals who received 2 doses of vaccine had significantly reduced NtAb titers against all SARS-CoV-2 strains compared to those infected and then vaccinated (≥1 dose), vaccinated (≥2 doses) and then infected, or those who received 3 doses of vaccine. Participants vaccinated with 2 or 3 doses of vaccine and then infected had the highest NtAb titers against all SARS-CoV-2 strains tested.

Conclusion

We assessed for the first time the NtAb response in food and retail workers. We found that vaccination prior to the emergence of Omicron BA.1 was associated with higher neutralizing activity against pre-Omicron variants, suggesting the importance of updating vaccines to increase antibody response against new SARS-CoV-2 variants. Vaccination followed by infection was associated with higher neutralizing activity against all SARS-CoV-2 strains tested.

Immunogenicity and safety of Sinovac-CoronaVac booster vaccinations in 12-17- year-olds with clinically significant reactions from Pfizer-BNT162b2 vaccination

Heterologous Sinovac-CoronaVac booster(s) in 12-17-year-olds who had a moderate/severe reaction to Pfizer-BNT162b2 mRNA vaccine was found to safe with no serious adverse events reported. In those primed with 1 dose of Pfizer-BNT162b2 vaccine, subsequent boosters with 2 doses of Sinovac-CoronaVac vaccines achieved neutralizing antibody levels which were comparable to those who had received 2 doses of Pfizer-BNT162b2 vaccines followed by 1 dose of Sinovac-CoronaVac vaccination. Adolescents with 1 Pfizer-BNT162b2 followed by 2 Sinovac-CoronaVac vaccines developed T-cell responses against broad peptides including membrane, nucleoprotein 1 and 2 but levels were highest for Spike protein and lasted until day 150 post-vaccination.

Superior antibody and membrane protein-specific T-cell responses to CoronaVac by intradermal versus intramuscular routes in adolescents

BACKGROUND

Optimising the immunogenicity of COVID-19 vaccines to improve their protection against disease is necessary. Fractional dosing by intradermal (ID) administration has been shown to be equally immunogenic as intramuscular (IM) administration for several vaccines, but the immunogenicity of ID inactivated whole severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the full dose is unknown. This study (NCT04800133) investigated the superiority of antibody and T-cell responses of full-dose CoronaVac by ID over IM administration in adolescents.

METHODS

Participants aged 11-17 years received two doses of IM or ID vaccine, followed by the 3rd dose 13-42 days later. Humoral and cellular immunogenicity outcomes were measured post-dose 2 (IM-CC versus ID-CC) and post-dose 3 (IM-CCC versus ID-CCC). Doses 2 and 3 were administered to 173 and 104 adolescents, respectively.

RESULTS

Spike protein (S) immunoglobulin G (IgG), S-receptor-binding domain (RBD) IgG, S IgG Fcγ receptor IIIa (FcγRIIIa)-binding, SNM [sum of individual (S), nucleocapsid protein (N), and membrane protein (M) peptide pool]-specific interleukin-2 (IL-2)+CD4+, SNM-specific IL-2+CD8+, S-specific IL-2+CD8+, N-specific IL-2+CD4+, N-specific IL-2+CD8+ and M-specific IL-2+CD4+ responses fulfilled the superior and non-inferior criteria for ID-CC compared to IM-CC, whereas IgG avidity was inferior. For ID-CCC, S-RBD IgG, surrogate virus neutralisation test, 90% plaque reduction neutralisation titre (PRNT90), PRNT50, S IgG avidity, S IgG FcγRIIIa-binding, M-specific IL-2+CD4+, interferon-γ+CD8+ and IL-2+CD8+ responses were superior and non-inferior to IM-CCC. The estimated vaccine efficacies were 49%, 52%, 66% and 79% for IM-CC, ID-CC, IM-CCC and ID-CCC, respectively. The ID groups reported more local, mild adverse reactions.

CONCLUSION

This is the first study to demonstrate superior antibody and M-specific T-cell responses by ID inactivated SARS-CoV-2 vaccination and serves as the basis for future research to improve the immunogenicity of inactivated vaccines.

Immunogenicity and safety of inactivated SARS-CoV-2 vaccine (CoronaVac) using two-dose primary protocol in children and adolescents (Immunita-002, Brazil): A phase IV six-month follow up

Introduction

Vaccines are essential for the prevention and control of several diseases, indeed, monitoring the immune response generated by vaccines is crucial. The immune response generated by vaccination against SARS-CoV-2 in children and adolescents is not well defined regarding to the intensity and medium to long-term duration of a protective immune response, which may point out the need of booster doses and might support the decisions in public health.

Objective

The study aims to evaluate the immunogenicity and safety of inactivated SARS-CoV-2 vaccine (CoronaVac) in a two-dose primary protocol in children and adolescent aging from 3 to 17 years old in Brazil.

Methods

Participants were invited to participate in the research at two public healthcare centers located in Serrana (São Paulo) and Belo Horizonte (Minas Gerais), Brazil. Participants underwent medical interviews to gather their medical history, including COVID-19 history and medical records. Physical exams were conducted, including weight, blood pressure, temperature, and pulse rate measurements. Blood samples were obtained from the participants before vaccination, 1 month after the first dose, and 1, 3, and 6 months after the second dose and were followed by a virtual platform for monitoring post-vaccination reactions and symptoms of COVID-19. SARS-CoV-2 genome from Swab samples of COVID-19 positive individuals were sequenced by NGS. Total antibodies were measured by ELISA and neutralizing antibodies to B.1 lineage and Omicron variant (BA.1) quantified by PRNT and VNT. The cellular immune response was evaluated by flow cytometry by the quantification of systemic soluble immune mediators.

Results

The follow-up of 640 participants showed that the CoronaVac vaccine (Sinovac/Butantan Institute) was able to significantly induce the production of total IgG antibodies to SARS-CoV-2 and the production of neutralizing antibodies to B.1 lineage and Omicron variant. In addition, a robust cellular immune response was observed with wide release of pro-inflammatory and regulatory mediators in the early post-immunization moments. Adverse events recorded so far have been mild and transient except for seven serious adverse events reported on VigiMed.

Conclusions

The results indicate a robust and sustained immune response induced by the CoronaVac vaccine in children and adolescents up to six months, providing evidences to support the safety and immunogenicity of this effective immunizer.

SARS-CoV-2 and innate immunity: the good, the bad, and the "goldilocks"

An ancient conflict between hosts and pathogens has driven the innate and adaptive arms of immunity. Knowledge about this interplay can not only help us identify biological mechanisms but also reveal pathogen vulnerabilities that can be leveraged therapeutically. The humoral response to SARS-CoV-2 infection has been the focus of intense research, and the role of the innate immune system has received significantly less attention. Here, we review current knowledge of the innate immune response to SARS-CoV-2 infection and the various means SARS-CoV-2 employs to evade innate defense systems. We also consider the role of innate immunity in SARS-CoV-2 vaccines and in the phenomenon of long COVID.

Prevalence and determinants of post-acute sequelae after SARS-CoV-2 infection (Long COVID) among adults in Mexico during 2022: a retrospective analysis of nationally representative data

Background

Post-acute sequelae after SARS-CoV-2 infection (PASC) remains a concerning long-term complication of COVID-19. Here, we aimed to characterize the epidemiology of PASC in Mexico during 2022 and identify potential associations of covariates with PASC prevalence using nationally representative data.

Methods

We analyzed data from the 2022 Mexican National Health and Nutrition Survey (ENSANUT) from 24,434 participants, representing 85,521,661 adults ≥20 years. PASC was defined using both the National Institute for Health and Care Excellence (NICE) definition and a PASC score ≥12. Estimates of PASC prevalence were stratified by age, sex, rural vs. urban setting, social lag quartiles, number of reinfections, vaccination status and periods of predominance of SARS-CoV-2 circulating variants. Determinants of PASC were assessed using log-binomial regression models adjusted by survey weights.

Findings

Persistent symptoms after SARS-CoV-2 infection were reported by 12.44% (95% CI 11.89-12.99) of adults ≥20 years in Mexico in 2022. The most common persistent symptoms were fatigue, musculoskeletal pain, headache, cough, loss of smell or taste, fever, post-exertional malaise, brain fog, anxiety, and chest pain. PASC was present in 21.21% (95% CI 19.74-22.68) of subjects with previously diagnosed COVID-19. Over 28.6% of patients with PASC reported symptoms persistence ≥6 months and 14.05% reported incapacitating symptoms. Higher PASC prevalence was associated with SARS-CoV-2 reinfections, depressive symptoms and living in states with high social lag. PASC prevalence, particularly its more severe forms, decreased with COVID-19 vaccination and for infections during periods of Omicron variant predominance.

Interpretation

PASC remains a significant public health burden in Mexico as the COVID-19 pandemic transitions into endemic. Promoting SARS-CoV-2 reinfection prevention and booster vaccination may be useful in reducing PASC burden.

Funding

This research was supported by Instituto Nacional de Geriatría in Mexico.

Humoral and Cellular Immunogenicity of 3 Doses of BNT162b2 in Children With Kidney Diseases

Introduction

Patients with severe kidney diseases are at risk of complications from COVID-19; however, little is known about the effectiveness of COVID-19 vaccines in children and adolescents with kidney diseases.

Methods

We investigated the immunogenicity and safety of an accelerated 3-dose primary series of COVID-19 vaccination among 59 pediatric patients with chronic kidney disease (CKD) (mean age 12.9 years; 30 male) with or without immunosuppression, dialysis, or kidney transplant. Dosage was 0.1 ml BNT162b2 to those aged 5 to 11 years, and 0.3 ml BNT162b2 to those aged 11 to 18 years.

Results

Three doses of either vaccine type elicited significant antibody responses that included spike receptor-binding domain (S-RBD) IgG (90.5%-93.8% seropositive) and surrogate virus neutralization (geometric mean sVNT% level, 78.6%-79.3%). There were notable T cell responses. Weaker neutralization responses were observed among those on immunosuppression, especially those receiving higher number of immunosuppressants or on mycophenolate mofetil. Neutralization was reduced against Omicron BA.1 compared to wild type (WT, i.e., ancestral) (post-dose 3 sVNT% level; 82.7% vs. 27.4%; P < 0.0001). However, the T cell response against Omicron BA.1 was preserved, which likely confers protection against severe COVID-19. Infected patients exhibited hybrid immunity after vaccination, as evidenced by the higher Omicron BA.1 neutralization response among these infected patients who received 2 doses compared with those who were uninfected. Generally mild or moderate adverse reactions following vaccines were reported.

Conclusion

An accelerated 3-dose primary series with BNT162b2 is immunogenic and safe in young children and adolescents with kidney diseases.

Age- and sex-specific differences in immune responses to BNT162b2 COVID-19 and live-attenuated influenza vaccines in UK adolescents

Introduction

The key to understanding the COVID-19 correlates of protection is assessing vaccine-induced immunity in different demographic groups. Young people are at a lower risk of COVID-19 mortality, females are at a lower risk than males, and females often generate stronger immune responses to vaccination.

Methods

We studied immune responses to two doses of BNT162b2 Pfizer COVID-19 vaccine in an adolescent cohort (n = 34, ages 12-16), an age group previously shown to elicit significantly greater immune responses to the same vaccine than young adults. Adolescents were studied with the aim of comparing their response to BNT162b2 to that of adults; and to assess the impacts of other factors such as sex, ongoing SARS-CoV-2 infection in schools, and prior exposure to endemic coronaviruses that circulate at high levels in young people. At the same time, we were able to evaluate immune responses to the co-administered live attenuated influenza vaccine. Blood samples from 34 adolescents taken before and after vaccination with COVID-19 and influenza vaccines were assayed for SARS-CoV-2-specific IgG and neutralising antibodies and cellular immunity specific for SARS-CoV-2 and endemic betacoronaviruses. The IgG targeting influenza lineages contained in the influenza vaccine were also assessed.

Results

Robust neutralising responses were identified in previously infected adolescents after one dose, and two doses were required in infection-naïve adolescents. As previously demonstrated, total IgG responses to SARS-CoV-2 Spike were significantly higher among vaccinated adolescents than among adults (aged 32-52) who received the BNT162b2 vaccine (comparing infection-naïve, 49,696 vs. 33,339; p = 0.03; comparing SARS-CoV-2 previously infected, 743,691 vs. 269,985; p <0.0001) by the MSD v-plex assay. There was no evidence of a stronger vaccine-induced immunity in females compared than in males.

Discussion

These findings may result from the introduction of novel mRNA vaccination platforms, generating patterns of immunity divergent from established trends and providing new insights into what might be protective following COVID-19 vaccination.

Humoral immunity against SARS-CoV-2 evoked by heterologous vaccination groups using the CoronaVac (Sinovac) and BNT162b2 (Pfizer/BioNTech) vaccines in Chile

Introduction

Severe acute respiratory syndrome virus 2 (SARS-CoV-2) has caused over million deaths worldwide, with more than 61,000 deaths in Chile. The Chilean government has implemented a vaccination program against SARS-CoV-2, with over 17.7 million people receiving a complete vaccination scheme. The final target is 18 million individuals. The most common vaccines used in Chile are CoronaVac (Sinovac) and BNT162b2 (Pfizer-Biotech). Given the global need for vaccine boosters to combat the impact of emerging virus variants, studying the immune response to SARS-CoV-2 is crucial. In this study, we characterize the humoral immune response in inoculated volunteers from Chile who received vaccination schemes consisting of two doses of CoronaVac [CoronaVac (2x)], two doses of CoronaVac plus one dose of BNT162b2 [CoronaVac (2x) + BNT162b2 (1x)], and three doses of BNT162b2 [BNT162b2 (3x)].

Methods

We recruited 469 participants from Clínica Dávila in Santiago and the Health Center Víctor Manuel Fernández in the city of Concepción, Chile. Additionally, we included participants who had recovered from COVID-19 but were not vaccinated (RCN). We analyzed antibodies, including anti-N, anti-S1-RBD, and neutralizing antibodies against SARS-CoV-2.

Results

We found that antibodies against the SARS-CoV-2 nucleoprotein were significantly higher in the CoronaVac (2x) and RCN groups compared to the CoronaVac (2x) + BNT162b2 (1x) or BNT162b2 (3x) groups. However, the CoronaVac (2x) + BNT162b2 (1x) and BNT162b2 (3x) groups exhibited a higher concentration of S1-RBD antibodies than the CoronaVac (2x) group and RCN group. There were no significant differences in S1-RBD antibody titers between the CoronaVac (2x) + BNT162b2 (1x) and BNT162b2 (3x) groups. Finally, the group immunized with BNT162b2 (3x) had higher levels of neutralizing antibodies compared to the RCN group, as well as the CoronaVac (2x) and CoronaVac (2x) + BNT162b2 (1x) groups.

Discussion

These findings suggest that vaccination induces the secretion of antibodies against SARS-CoV-2, and a booster dose of BNT162b2 is necessary to generate a protective immune response. In the current state of the pandemic, these data support the Ministry of Health of the Government of Chile's decision to promote heterologous vaccination as they indicate that a significant portion of the Chilean population has neutralizing antibodies against SARS-CoV-2.

SARS-CoV-2 mRNA Vaccine Elicits Sustained T Cell Responses Against the Omicron Variant in Adolescents

Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been acknowledged as an effective mean of preventing infection and hospitalization. However, the emergence of highly transmissible SARS-CoV-2 variants of concern (VOCs) has led to substantial increase in infections among children and adolescents. Vaccine-induced immunity and longevity have not been well defined in this population. Therefore, we aimed to analyze humoral and cellular immune responses against ancestral and SARS-CoV-2 variants after two shots of the BNT162b2 vaccine in healthy adolescents. Although vaccination induced a robust increase of spike-specific binding Abs and neutralizing Abs against the ancestral and SARS-CoV-2 variants, the neutralizing activity against the Omicron variant was significantly low. On the contrary, vaccine-induced memory CD4+ T cells exhibited substantial responses against both ancestral and Omicron spike proteins. Notably, CD4+ T cell responses against both ancestral and Omicron strains were preserved at 3 months after two shots of the BNT162b2 vaccine without waning. Polyfunctionality of vaccine-induced memory T cells was also preserved in response to Omicron spike protein. The present findings characterize the protective immunity of vaccination for adolescents in the era of continuous emergence of variants/subvariants.

Humoral immune responses to inactivated COVID-19 vaccine up to 1 year in children with chronic hepatitis B infection

Background

Inactivated SARS-CoV-2 vaccination has recently been approved for children aged 3-17 years in China. However, data on long-term humoral responses to inactivated vaccines in children with chronic hepatitis B (CHB) are still limited.

Methods

In this prospective observational study, CHB children after primary inactivated SARS-CoV-2 vaccines were recruited consecutively and followed up for 1 year. CHB adults from another cohort study (NCT05007665) were used as a control. The receptor-binding domain IgG antibody (anti-RBD-IgG), neutralizing antibody (NAb), neutralization against Omicron (BA2.12.1, BA.4 and BA.5), and memory B -cell (MBC) responses were evaluated.

Results

Overall, 115 CHB children and 351 CHB adults were included in this analysis. The antibody titers decreased over the first ~180 days and then plateaued up to 1 year in CHB children. However, lower and faster declines in antibody responses were observed in CHB adults. Interestingly, the seroprevalence of antibodies was still high after over 8 months in CHB children (anti-RBD-IgG [90%] and NAbs [83%]). However, neutralization against Omicron subvariants was significantly reduced in CHB children (-3.68-fold to -8.60-fold). Notably, neutralization against the BA.5 subvariant was obviously diminished in CHB children compared with adults. Moreover, CHB children had similar RBD-specific MBCs but higher RBD-specific atypical MBCs compared with adults.

Conclusion

Inactivated vaccination could elicit more robust and durable antibody responses to the wild-type SARS-CoV-2 strain in CHB children than in CHB adults but showed inferior responses to Omicron subvariants (especially to the BA.5 strain). Hence, new Omicron-related or all-in-one vaccines are needed immediately for CHB children.

T-cell immunity to SARS-CoV-2: what if the known best is not the optimal course for the long run? Adapting to evolving targets

Humanity did surprisingly well so far, considering how unprepared it was to respond to the coronavirus disease 2019 (COVID-19) threat. By blending old and ingenious new technology in the context of the accumulated knowledge on other human coronaviruses, several vaccine candidates were produced and tested in clinical trials in record time. Today, five vaccines account for the bulk of the more than 13 billion doses administered worldwide. The ability to elicit biding and neutralizing antibodies most often against the spike protein is a major component of the protection conferred by immunization but alone it is not enough to limit virus transmission. Thus, the surge in numbers of infected individuals by newer variants of concern (VOCs) was not accompanied by a proportional increase in severe disease and death rate. This is likely due to antiviral T-cell responses, whose evasion is more difficult to achieve. The present review helps navigating the very large literature on T cell immunity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination. We examine the successes and shortcomings of the vaccinal protection in the light of the emergence of VOCs with breakthrough potential. SARS-CoV-2 and human beings will likely coexist for a long while: it will be necessary to update existing vaccines to improve T-cell responses and attain better protection against COVID-19.

Hesitancy, reactogenicity and immunogenicity of the mRNA and whole-virus inactivated Covid-19 vaccines in pediatric neuromuscular diseases

The mRNA-based BNT162b2 and inactivated whole-virus CoronaVac are two widely used COVID-19 vaccines that confer immune protection to healthy individuals. However, hesitancy toward COVID-19 vaccination appeared to be common for patients with neuromuscular diseases (NMDs) due to the paucity of data on the safety and efficacy in this high-risk patient population. Therefore, we examined the underlying factors associated with vaccine hesitancy across time for NMDs and assessed the reactogenicity and immunogenicity of these two vaccines. Patients aged 8-18 years with no cognitive delay were invited to complete surveys in January and April 2022. Patients aged 2-21 years were enrolled for COVID-19 vaccination between June 2021 and April 2022, and they recorded adverse reactions (ARs) for 7 days after vaccination. Peripheral blood was obtained before and within 49 days after vaccination to measure serological antibody responses compared to healthy children and adolescents. Forty-one patients completed vaccine hesitancy surveys for both timepoints, while 22 joined the reactogenicity and immunogenicity arm of the study. Two or more family members vaccinated against COVID-19 was positively associated with intention of vaccination (odds ratio 11.7, 95% CI 1.81-75.1, p = .010). Pain at the injection site, fatigue, and myalgia were the commonest ARs. Most ARs were mild (75.5%, n = 71/94). All 19 patients seroconverted against the wildtype SARS-CoV-2 after two doses of either vaccine, similar to 280 healthy counterparts. There was lower neutralization against the Omicron BA.1 variant. BNT162b2 and CoronaVac were safe and immunogenic for patients with NMDs, even in those on low-dose corticosteroids.

Comparing T- and B-cell responses to COVID-19 vaccines across varied immune backgrounds

The emergence of adapted variants of the SARS-CoV-2 virus has led to a surge in breakthrough infections worldwide. A recent analysis of immune responses in people who received inactivated vaccines has revealed that individuals with no prior infection have limited resistance to Omicron and its sub-lineages, while those with previous infections exhibit a significant amount of neutralizing antibodies and memory B cells. However, specific T-cell responses remain largely unaffected by the mutations, indicating that T-cell-mediated cellular immunity can still provide protection. Moreover, the administration of a third dose of vaccine has resulted in a marked increase in the spectrum and duration of neutralizing antibodies and memory B cells in vivo, which has enhanced resistance to emerging variants such as BA.2.75 and BA.2.12.1. These results highlight the need to consider booster immunization for previously infected individuals and the development of novel vaccination strategies. The rapid spread of adapted variants of the SARS-CoV-2 virus presents a significant challenge to global health. The findings from this study underscore the importance of tailoring vaccination strategies based on individual immune backgrounds and the potential need for booster shots to combat emerging variants. Continued research and development are crucial to discovering new immunization strategies that will effectively protect public health against the evolving virus.

Varying Cellular Immune Response against SARS-CoV-2 after the Booster Vaccination: A Cohort Study from Fukushima Vaccination Community Survey, Japan

Booster vaccination reduces the incidence of severe cases and mortality related to COVID-19, with cellular immunity playing an important role. However, little is known about the proportion of the population that has achieved cellular immunity after booster vaccination. Thus, we conducted a Fukushima cohort database and assessed humoral and cellular immunity in 2526 residents and healthcare workers in Fukushima Prefecture in Japan through continuous blood collection every 3 months from September 2021. We identified the proportion of people with induced cellular immunity after booster vaccination using the T-SPOT.COVID test, and analyzed their background characteristics. Among 1089 participants, 64.3% (700/1089) had reactive cellular immunity after booster vaccination. Multivariable analysis revealed the following independent predictors of reactive cellular immunity: age < 40 years (adjusted odds ratio: 1.81; 95% confidence interval: 1.19-2.75; p-value: 0.005) and adverse reactions after vaccination (1.92, 1.19-3.09, 0.007). Notably, despite IgG(S) and neutralizing antibody titers of ≥500 AU/mL, 33.9% (349/1031) and 33.5% (341/1017) of participants, respectively, did not have reactive cellular immunity. In summary, this is the first study to evaluate cellular immunity at the population level after booster vaccination using the T-SPOT.COVID test, albeit with several limitations. Future studies will need to evaluate previously infected subjects and their T-cell subsets.

Non-spike and spike-specific memory T cell responses after the third dose of inactivated COVID-19 vaccine

Background

During the COVID-19 epidemic, vaccination has become the most safe and effective way to prevent severe illness and death. Inactivated vaccines are the most widely used type of COVID-19 vaccines in the world. In contrast to spike-based mRNA/protein COVID-19 vaccines, inactivated vaccines generate antibodies and T cell responses against both spike and non-spike antigens. However, the knowledge of inactivated vaccines in inducing non-spike-specific T cell response is very limited.

Methods

In this study, eighteen healthcare volunteers received a homogenous booster (third) dose of the CoronaVac vaccine at least 6 months after the second dose. CD4+ and CD8+ T cell responses against a peptide pool from wild-type (WT) non-spike proteins and spike peptide pools from WT, Delta, and Omicron SARS-CoV-2 were examined before and 1-2 weeks after the booster dose.

Results

The booster dose elevated cytokine response in CD4+ and CD8+ T cells as well as expression of cytotoxic marker CD107a in CD8+ T cells in response to non-spike and spike antigens. The frequencies of cytokine-secreting non-spike-specific CD4+ and CD8+ T cells correlated well with those of spike-specific from WT, Delta, and Omicron. Activation-induced markers (AIM) assay also revealed that booster vaccination elicited non-spike-specific CD4+ and CD8+ T cell responses. In addition, booster vaccination produced similar spike-specific AIM+CD4+ and AIM+CD8+ T cell responses to WT, Delta, and Omicron, indicting strong cross-reactivity of functional cellular response between WT and variants. Furthermore, booster vaccination induced effector memory phenotypes of spike-specific and non-spike-specific CD4+ and CD8+ T cells.

Conclusions

These data suggest that the booster dose of inactive vaccines broadens both non-spike-specific and spike-specific T cell responses against SARS-CoV-2.

Human memory T cell dynamics after aluminum-adjuvanted inactivated whole-virion SARS-CoV-2 vaccination

This study evaluates the functional capacity of CD4+ and CD8+ terminally-differentiated effector (TEMRA), central memory (TCM), and effector memory (TEM) cells obtained from the volunteers vaccinated with an aluminum-adjuvanted inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac). The volunteers were followed for T cell immune responses following the termination of a randomized phase III clinical trial. Seven days and four months after the second dose of the vaccine, the memory T cell subsets were collected and stimulated by autologous monocyte-derived dendritic cells (mDCs) loaded with SARS-CoV-2 spike glycoprotein S1. Compared to the placebo group, memory T cells from the vaccinated individuals significantly proliferated in response to S1-loaded mDCs. CD4+ and CD8+ memory T cell proliferation was detected in 86% and 78% of the vaccinated individuals, respectively. More than 73% (after a short-term) and 62% (after an intermediate-term) of the vaccinated individuals harbored TCM and/or TEM cells that responded to S1-loaded mDCs by secreting IFN-γ. The expression of CD25, CD38, 4-1BB, PD-1, and CD107a indicated a modulation in the memory T cell subsets. Especially on day 120, PD-1 was upregulated on CD4+ TEMRA and TCM, and on CD8+ TEM and TCM cells; accordingly, proliferation and IFN-γ secretion capacities tended to decline after 4 months. In conclusion, the combination of inactivated whole-virion particles with aluminum adjuvants possesses capacities to induce functional T cell responses.

COVID-19 vaccines versus pediatric hospitalization

Vaccine effectiveness of BNT162b2 and CoronaVac against COVID-19-associated hospitalization and moderate-to-severe disease due to SARS-CoV-2 Omicron BA.2 is studied from the 1.36 million doses administered to 766,601 of 953,400 children aged 3-11 years and adolescents aged 12-18 years in Hong Kong as of April 2022. These vaccines confer substantial protection.

Effectiveness of BNT162b2 and CoronaVac in children and adolescents against SARS-CoV-2 infection during Omicron BA.2 wave in Hong Kong

BACKGROUND

The SARS-CoV-2 Omicron BA.2 subvariant replaced BA.1 globally in early 2022, and caused an unprecedented tsunami of cases in Hong Kong, resulting in the collapse of elimination strategy. Vaccine effectiveness (VE) of BNT162b2 and CoronaVac against BA.2 is unclear.

METHODS

We utilize an ecological design incorporating population-level vaccine coverage statistics and territory-wide case-level SARS-CoV-2 infection surveillance data, and investigate the VE against infection during the Omicron BA.2 wave between January 1 to April 19, 2022, in Hong Kong for children and adolescents.

RESULTS

We estimate VE to be 33.0% for 1 dose of BNT162b2 in children aged 5-11 and 40.8% for 2 doses of CoronaVac in children aged 3-11. We also estimate 54.9% VE for 2 doses of BNT162b2, and 55.0% VE for 2 doses of CoronaVac in adolescents aged 12-18.

CONCLUSIONS

Our findings support partly preserved VE against infection by variants of concerns for children and adolescents in settings with extremely low levels of prior SARS-CoV-2 circulation.

Comparison of humoral and cellular immune responses between ChAd-BNT heterologous vaccination and BNT-BNT homologous vaccination following the third BNT dose: A prospective cohort study

Introduction

The differential immune responses after two additional BNT162b2 (BNT) booster doses between ChAdOx1 nCoV-10 (ChAd)-primed and BNT-primed groups have not been elucidated. The aim of this study was to compare vaccine-induced humoral and cellular immune responses and evaluate breakthrough infection between the two vaccination strategies.

Methods

In 221 healthy subjects (111 in the ChAd group), longitudinal immune responses were monitored at 3, 4, and 6 months after the 2nd dose and 1, 3, and 6 months after the 3rd dose. Humoral immunity was measured by two fully automated chemiluminescent immunoassays (Elecsys and Abbott) and a surrogate virus neutralization test (sVNT). Cellular immunity was assessed by two interferon-γ (IFN-γ) release assays (QuantiFERON SARS-CoV-2 and Covi-FERON).

Results

After the 2nd dose of BNT vaccination, total antibody levels were higher in the ChAd group, but IgG antibody and sVNT results were higher in the BNT group. Following the 3rd dose vaccination, binding antibody titers were significantly elevated in both groups (ChAD-BNT; 15.4 to 17.8-fold, BNT-BNT; 22.2 to 24.6-fold), and the neutralizing capacity was increased by 1.3-fold in both cohorts. The ChAd-BNT group had lower omicron neutralization positivity than the BNT-BNT group (P = 0.001) at 6 months after the 3rd dose. Cellular responses to the spike antigen also showed 1.7 to 3.0-fold increases after the 3rd dose, which gradually declined to the levels equivalent to before the 3rd vaccination. The ChAd cohort tended to have higher IFN-γ level than the BNT cohort for 3-6 months after the 2nd and 3rd doses. The frequency of breakthrough infection was higher in the ChAd group (44.8%) than in the BNT group (28.1%) (P = 0.0219). Breakthrough infection induced increased humoral responses in both groups, and increase of cellular response was significant in the ChAd group.

Discussion

Our study showed differential humoral and cellular immune responses between ChAd-BNT-BNT heterologous and BNT-BNT-BNT homologous vaccination cohorts. The occurrence of low antibody levels in the ChAd-primed cohort in the humoral immune response may be associated with an increased incidence of breakthrough infections. Further studies are needed on the benefits of enhanced cellular immunity in ChAd-primed cohorts.

Antibody and T cell responses against wild-type and Omicron SARS-CoV-2 after third-dose BNT162b2 in adolescents

The high effectiveness of the third dose of BNT162b2 in healthy adolescents against Omicron BA.1 has been reported in some studies, but immune responses conferring this protection are not yet elucidated. In this analysis, our study (NCT04800133) aims to evaluate the humoral and cellular responses against wild-type and Omicron (BA.1, BA.2 and/or BA.5) SARS-CoV-2 before and after a third dose of BNT162b2 in healthy adolescents. At 5 months after 2 doses, S IgG, S IgG Fc receptor-binding, and neutralising antibody responses waned significantly, yet neutralising antibodies remained detectable in all tested adolescents and S IgG avidity increased from 1 month after 2 doses. The antibody responses and S-specific IFN-γ⁺ and IL-2⁺ CD8⁺ T cell responses were significantly boosted in healthy adolescents after a homologous third dose of BNT162b2. Compared to adults, humoral responses for the third dose were non-inferior or superior in adolescents. The S-specific IFN-γ⁺ and IL-2⁺ CD4⁺ and CD8⁺ T cell responses in adolescents and adults were comparable or non-inferior. Interestingly, after 3 doses, adolescents had preserved S IgG, S IgG avidity, S IgG FcγRIIIa-binding, against Omicron BA.2, as well as preserved cellular responses against BA.1 S and moderate neutralisation levels against BA.1, BA.2 and BA.5. Sera from 100 and 96% of adolescents tested at 1 and 5 months after two doses could also neutralise BA.1. Our study found high antibody and T cell responses, including potent cross-variant reactivity, after three doses of BNT162b2 vaccine in adolescents in its current formulation, suggesting that current vaccines can be protective against symptomatic Omicron disease.

Immunogenicity and safety of BNT162b2 mRNA vaccine in Chinese adults: A phase 2 randomised clinical trial

BACKGROUND

BNT162b2, an mRNA vaccine against COVID-19, is being utilised worldwide, but immunogenicity and safety data in Chinese individuals are limited.

METHODS

This phase 2, randomised, double-blind, placebo-controlled trial included healthy or medically stable individuals aged 18-85 years enrolled at two clinical sites in China. Participants were stratified by age (≤55 or >55 years) and randomly assigned (3:1) by an independent randomisation professional to receive two doses of intramuscular BNT162b2 30 μg or placebo, administered 21 days apart. Study participants, study personnel, investigators, statisticians, and the sponsor's study management team were blinded to treatment assignment. Primary immunogenicity endpoints were the geometric mean titers (GMTs) of neutralising antibodies to live severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and seroconversion rates (SCR) 1 month after the second dose. Safety assessments included reactogenicity within 14 days of vaccination, adverse events (AEs), and clinical laboratory parameters. Randomised participants who received at least one dose were included in the efficacy and safety analyses on a complete case basis (incomplete/missing data not imputed). Results up to 6 months after the second dose are reported.

FINDINGS

Overall, 959 participants (all of Han ethnicity) who were recruited between December 5th, 2020 and January 9th, 2021 received at least one injection (BNT162b2, n=720; placebo, n=239). At 1 month after the second dose, the 50% neutralising antibody GMT was 294.4 (95% CI; 281.1-308.4) in the BNT162b2 group and 5.0 (95% CI; 5.0-5.0) in the placebo group. SCRs were 99.7% (95% CI; 99.0%-100.0%) and 0% (95% CI; 0.0%-1.5%), respectively (p<0.0001 vs placebo). Although the GMT of neutralising antibodies in the BNT162b2 group was greatly reduced at 6 months after the second dose, the SCR still remained at 58.8%. BNT162b2-elicited sera neutralised SARS-CoV-2 variants of concern. T-cell responses were detected in 58/73 (79.5%) BNT162b2 recipients. Reactogenicity was mild or moderate in severity and resolved within a few days after onset. Unsolicited AEs were uncommon at 1 month following vaccine administration, and there were no vaccine-related serious AEs at 1 month or 6 months after the second dose.

INTERPRETATION

BNT162b2 vaccination induced a robust immune response with acceptable tolerability in Han Chinese adults. However, follow-up duration was relatively short and COVID-19 rates were not assessed. Safety data collection is continuing until 12 months after the second dose.

FUNDING

BioNTech - sponsored the trial. Shanghai Fosun Pharmaceutical Development Inc. (Fosun Pharma) - conducted the trial, funded medical writing.

CLINICALTRIALSGOV REGISTRATION NUMBER

NCT04649021. Trial status: Completed.

Post-vaccination SARS-CoV-2 seroprevalence in children aged 3-11 years and the positivity in unvaccinated children: A retrospective, single-center study

OBJECTIVE

To analyze the positivity and levels of SARS-CoV-2 antibodies in vaccinated children to evaluate the humoral immune response of vaccination on pediatric population. Analysis on the causes of antibody positivity in unvaccinated children.

METHODS

A retrospective study was conducted on children who were admitted to the Children's Hospital Affiliated to Capital Institute of Pediatrics. The clinical data of serological testing of SARS-CoV-2 immunoglobulin M (IgM) and IgG antibodies were collected from SARS-CoV-2 vaccinated or unvaccinated children with no evidence of prior novel coronavirus infection. Chemiluminescence immunoassay was utilized for the in vitro determination of SARS-CoV-2 antibodies.

RESULTS

A total of 3,321 healthy children aged 6-11 years received two doses of inactivated SARS-CoV-2 vaccine. At 1 month after the second dose, the positive rate (96.5%) and levels [8.039 (interquartile range (IQR), 6.067-9.098)] of SARS-CoV-2 IgG antibodies reached the peak and remained at a high level for 2-3 months, after which the positive rate and level of vaccine-induced IgG antibody gradually decreased. Compared with 1 month after the second dose of vaccine, the positive rate of IgG antibody decreased to 70.4% at 7 months, and the antibody level decreased by 69.0%. A total of 945 children aged 3-5 years received one or two doses of inactivated vaccine. The positive rate and levels of SARS-CoV-2 IgG antibody in participants remained high for 3 months after vaccination. There was no gender-based difference in positive rate of IgG antibody in children aged 3-11 years old (P>0.05). Among the 5,309 unvaccinated children aged 0 day to 11 years, 105 (2.0%) were positive for SARS-CoV-2 IgG antibody, which was associated with passive infusion. The maternal humoral response to COVID-19 vaccination in noninfected pregnant women was transferred through the placenta to the fetus, and some children obtained SARS-CoV-2-positive antibodies through blood transfusion.

CONCLUSIONS

Inactivated SARS-CoV-2 vaccines could induce robust humoral immune response that gradually declined within several months after the second dose. Therefore, it helps to determine whether children receive a booster dose and elicit a long-term memory immune response. Positive SARS-CoV-2 antibodies in unvaccinated children were associated with passive IgG antibody infusion.

Safety after BBIBP-CorV (Sinopharm) COVID-19 Vaccine in Adolescents Aged 10-17 Years in Thailand

Coronavirus disease 2019 affected child health and impacted learning because of the resulting onsite school closures. This prospective cohort study included children aged 10-17 who received two 4 µg doses of BBIBP-CorV administered intramuscularly 21-28 days apart. To assess vaccine safety, 36,808 participants were then followed with paper- and web-based online questionnaire surveys that captured local and systemic reactogenicities following vaccine administration on days 1, 7, and 30. Among participants, 76% (27,880) reported reactogenicity within the first 24 h and 7 days following the first dose. Half (51.41%) of participants experienced pain at the injection site; the majority of cases were mild in severity. Injection site tenderness (37.93%) was another common local reaction. Fatigue (37.89%), myalgia (33.56%), and headache (26.76%) were the most common systemic reactions. On days 2-7 after the first dose, 25.85% of participants experienced adverse reactions. Following the second dose, reactogenicity was 7.6% and 1.09% within 24 h and between days 2-7. The majority of reactions were of mild to moderate severity. We report that two doses of the BBIBP-CorV caused mild to moderate side effects in adolescents in Thailand. The findings confirm the vaccine's safety profile in this age group.

The lymphatic system and COVID-19 vaccines

Understanding the precise mechanism of vaccine-induced protection and the immune correlates of protection against coronavirus disease 2019 (COVID-19) is crucially important for developing next-generation vaccines that confer durable and protective immunity against COVID-19. Similar factors are also important for other infectious diseases. Here, I briefly summarize the mechanism of action of the currently used COVID-19 mRNA vaccines from the viewpoint of the function of the lymphatic system.

A comparative characterization of SARS-CoV-2-specific T cells induced by mRNA or inactive virus COVID-19 vaccines

Unlike mRNA vaccines based only on the spike protein, inactivated severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines should induce a diversified T cell response recognizing distinct structural proteins. Here, we perform a comparative analysis of SARS-CoV-2-specific T cells in healthy individuals following vaccination with inactivated SARS-CoV-2 or mRNA vaccines. Relative to spike mRNA vaccination, inactivated vaccines elicit a lower magnitude of spike-specific T cells, but the combination of membrane, nucleoprotein, and spike-specific T cell response is quantitatively comparable with the sole spike T cell response induced by mRNA vaccine, and they efficiently tolerate the mutations characterizing the Omicron lineage. However, this multi-protein-specific T cell response is not mediated by a coordinated CD4 and CD8 T cell expansion but by selective priming of CD4 T cells. These findings can help in understanding the role of CD4 and CD8 T cells in the efficacy of the different vaccines to control severe COVID-19 after Omicron infection.

Safety and immunogenicity of 3 doses of BNT162b2 and CoronaVac in children and adults with inborn errors of immunity

Our study (NCT04800133) aimed to determine the safety and immunogenicity in patients with IEIs receiving a 3-dose primary series of mRNA vaccine BNT162b2 (age 12+) or inactivated whole-virion vaccine CoronaVac (age 3+) in Hong Kong, including Omicron BA.1 neutralization, in a nonrandomized manner. Intradermal vaccination was also studied. Thirty-nine patients were vaccinated, including 16 with homologous intramuscular 0.3ml BNT162b2 and 17 with homologous intramuscular 0.5ml CoronaVac. Two patients received 3 doses of intradermal 0.5ml CoronaVac, and 4 patients received 2 doses of intramuscular BNT162b2 and the third dose with intradermal BNT162b2. No safety concerns were identified. Inadequate S-RBD IgG and surrogate virus neutralization responses were found after 2 doses in patients with humoral immunodeficiencies and especially so against BA.1. Dose 3 of either vaccine increased S-RBD IgG response. T cell responses against SARS-CoV-2 antigens were detected in vaccinated IEI patients by intracellular cytokine staining on flow cytometry. Intradermal third dose vaccine led to high antibody response in 4 patients. The primary vaccination series of BNT162b2 and CoronaVac in adults and children with IEIs should include 3 doses for optimal immunogenicity.