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Despite remarkable progress in the treatment of hepatitis C virus (HCV) infection, it remains a significant global health burden, necessitating the development of an effective prophylactic vaccine. This review paper presents the current landscape of HCV vaccine candidates and approaches, including more traditional, based on inactivated virus, and more modern, such as subunit protein, vectored, based on nucleic acids (DNA and mRNA) and virus-like particles. The concept of the HCV vaccine is first put in the context of viral genetic diversity and adaptive responses to HCV infection, an understanding of which is crucial in guiding the development of an effective vaccine against such a complex virus. Because ethical dimensions are also significant in vaccine research, development, and potential deployment, we also address them in this paper. The road to a safe and effective vaccine to prevent HCV infection remains bumpy due to the genetic variation of HCV and its ability to evade immune responses. The progress in cell-culture systems allowed for the production of an inactivated HCV vaccine candidate, which can induce cross-neutralizing antibodies in vitro, but whether this could prevent infection in humans is unknown. Subunit protein vaccine candidates that entered clinical trials elicited HCV-specific humoral and cellular responses, though it remains to be shown whether they translate into effective prevention of HCV infection or progression of infection to a chronic state. Such responses were also induced by a clinically tested vector-based vaccine candidate, which decreased the viral HCV load but did not prevent chronic HCV infection. These disappointments were not readily predicted from preclinical animal studies. The vaccine platforms employing virus-like particles, DNA, and mRNA provide opportunities for the HCV vaccine, but their potential in this context has yet to be shown. Ensuring the designed vaccine is based on conserved epitope(s) and elicits broadly neutralizing immune responses is also essential. Given failures in developing a prophylactic HCV vaccine, it is crucial to continue supporting national strategies, including funding for screening and treatment programs. However, these actions are likely insufficient to permanently control the HCV burden, encouraging further mobilization of significant resources for HCV vaccine research as a missing element in the elimination of viral hepatitis as a global public health.

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The present study aimed to evaluate the effectiveness of two doses of CoronaVac in preventing SARS-CoV-2 symptomatic disease with virological confirmation, as well as in the prevention of COVID-19 moderate and severe cases. A test-negative unmatched case-control design was used, in which cases were patients with suspected COVID-19 (presenting at least two of the following symptoms: fever, chills, sore throat, headache, cough, runny nose, olfactory or taste disorders) with virological confirmation, and controls were those whose SARS-CoV-2 test was negative. As for exposure, participants were classified as unvaccinated, or vaccinated with a complete schedule. Suspected COVID-19 cases were identified from March to November 2021, in two cities located in the State of São Paulo, Brazil. All participants signed the Informed Consent Form before enrollment. RT-PCR results and vaccination data were obtained from the local surveillance systems. Up to two phone calls were made to obtain information on the outcome of the cases. A total of 2981 potential participants were screened for eligibility, of which 2163 were included, being 493 cases and 1670 controls. Vaccination, age, the reported contact with a COVID-19 suspected or confirmed case in the 14 days before symptoms onset, and the educational level were the variables independently associated with the outcome. The adjusted vaccine effectiveness for symptomatic COVID-19 (AVE) was 39.0 % (95 % CI 6.0-60.0 %). The AVE in the prevention of moderate and severe disease was 91.0 % (95 % CI 76.0-97.0 %). Our results were influenced by the waning of the Gamma variant, in the second trimester of 2021, followed by the increase in vaccination coverage, and a drop in the number of cases in the second half of the year. The study demonstrated the high effectiveness of CoronaVac in preventing moderate/severe COVID-19 cases.

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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.

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At the end of 2022, a huge tide of SARS-CoV-2 infection mainly Omicron BA.4/5 developed in China. Multiple myeloma (MM) patients suffered cancer deterioration and mortality from COVID-19, yet profound analyses of Omicron variants-induced immunity function are scarce. We presented a longitudinal study in 218 MM patients and 73 healthy controls (HCs), reporting the prognostic factors and dynamic humoral and cellular immune responses. Neutralizing antibody and interferon γ ELISpot assay of SARS-CoV-2 was tested at three time points: 2-4, 8-10, and 14-16 weeks after infections. Our data showed older age, active MM, relapsed/refractory MM (R/RMM), immunotherapy, comorbidity, and non-vaccination were risk factors associated with hospitalization. Severe humoral immunity impairment within 2-4 weeks was especially seen in patients with unvaccinated, older age, immunotherapy, R/RMM and comorbidities, while T-cell response was relatively intact. Although antibodies of Omicron variants reached positive levels in MM patients at 8-10 weeks, half lost effective antibody protection at 14-16 weeks. However, most seronegative patients (76.2% at 2-4 weeks, 83.3% at 8-10 weeks) could develop effective T-cell response. Notably, the inactivated wild-type vaccinated patients exhibited weaker humoral and cellular immunity only at 2-4 weeks, escalating to similar levels as those in HCs later. Our findings indicate impairment of humoral immunity at acute-phase after infection is the major factor correlated with hospitalization. One-month suspension of immune therapy is suggested to prevent serious infection. These results confirm the value of inactivated vaccine, but indicate the need for additional booster at 14-16 weeks after infection for high-risk MM population.

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Knowledge of the antibody response to the third dose of inactivated SARS-CoV-2 vaccines is crucial because it is the subject of one of the largest global vaccination programs. This study integrated microsampling with optical biosensors to profile neutralizing antibodies (NAbs) in fifteen vaccinated healthy donors, followed by the application of machine learning to predict antibody response at given timepoints. Over a nine-month duration, microsampling and venipuncture were conducted at seven individual timepoints. A refined iteration of a fiber optic biolayer interferometry (FO-BLI) biosensor was designed, enabling rapid multiplexed biosensing of the NAbs of both wild-type and Omicron SARS-CoV-2 variants in minutes. Findings revealed a strong correlation (Pearson r of 0.919, specificity of 100%) between wild-type variant NAb levels in microsamples and sera. Following the third dose, sera NAb levels of the wild-type variant increased 2.9-fold after seven days and 3.3-fold within a month, subsequently waning and becoming undetectable after three months. Considerable but incomplete evasion of the latest Omicron subvariants from booster vaccine-elicited NAbs was confirmed, although a higher number of binding antibodies (BAbs) was identified by another rapid FO-BLI biosensor in minutes. Significantly, FO-BLI highly correlated with a pseudovirus neutralization assay in identifying neutralizing capacities (Pearson r of 0.983). Additionally, machine learning demonstrated exceptional accuracy in predicting antibody levels, with an error level of <5% for both NAbs and BAbs across multiple timepoints. Microsample-driven biosensing enables individuals to access their results within hours of self-collection, while precise models could guide personalized vaccination strategies. The technology's innate adaptability means it has the potential for effective translation in disease prevention and vaccine development.

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BACKGROUND: Vaccination constitutes the best strategy against COVID-19. In Tunisia, seven vaccines standing for the three main platforms, namely RNA, viral vector, and inactivated vaccines, have been used to vaccinate the population at a large scale. This study aimed to assess, in our setting, the kinetics of vaccine-induced anti-RBD IgG and IgA antibody responses. METHODS: Using in-house developed and validated ELISA assays, we measured anti-RBD IgG and IgA serum antibodies in 186 vaccinated workers at the Institut Pasteur de Tunis over 12 months. RESULTS: We showed that RNA vaccines were the most immunogenic vaccines, as compared to alum-adjuvanted inactivated and viral-vector vaccines, either in SARS-CoV-2-naïve or in SARS-CoV-2-experienced individuals. In addition to the IgG antibodies, the vaccination elicited RBD-specific IgAs. Vaccinated individuals with prior SARS-CoV-2 infection exhibited more robust IgG and IgA antibody responses, as compared to SARS-CoV-2-naïve individuals. CONCLUSIONS: After following up for 12 months post-immunization, we concluded that the hierarchy between the platforms for anti-RBD antibody-titer dynamics was RNA vaccines, followed by viral-vector and alum-adjuvanted inactivated vaccines.

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Tick-borne encephalitis virus (TBEV) causes a severe disease, tick-borne encephalitis (TBE), that has a substantial epidemiological importance for Northern Eurasia. Between 10,000 and 15,000 TBE cases are registered annually despite the availability of effective formaldehyde-inactivated full-virion vaccines due to insufficient vaccination coverage, as well as sporadic cases of vaccine breakthrough. The development of improved vaccines would benefit from the atomic resolution structure of the antigen. Here we report the refined single-particle cryo-electron microscopy (cryo-EM) structure of the inactivated mature TBEV vaccine strain Sofjin-Chumakov (Far-Eastern subtype) at a resolution of 3.0 Å. The increase of the resolution with respect to the previously published structures of TBEV strains Hypr and Kuutsalo-14 (European subtype) was reached due to improvement of the virus sample quality achieved by the optimized preparation methods. All the surface epitopes of TBEV were structurally conserved in the inactivated virions. ELISA studies with monoclonal antibodies supported the hypothesis of TBEV protein shell cross-linking upon inactivation with formaldehyde.

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The continuous evolution and mutation of SARS-CoV-2 have highlighted the need for more effective vaccines. In this study, CpG, MF59-like, and Alum adjuvant Delta strain inactivated SARS-CoV-2 vaccines were prepared, and the immunogenicity of these vaccines in mice was evaluated. The Delta + MF59-like vaccine group produced the highest levels of S- and RBD-binding antibodies and live Delta virus neutralization levels after one shot of immunization, while mice in the Delta + Alum vaccine group had the highest levels of these antibodies after two doses, and the Delta + MF59-like and Delta + Alum vaccine groups produced high levels of cross-neutralization antibodies against prototype, Beta, and Gamma strain SARS-CoV-2 viruses. There was no significant decrease in neutralizing antibody levels in any vaccine group during the observation period. CpG, MF59-like, and Alum adjuvant Delta strain inactivated SARS-CoV-2 vaccines excited different antibody subtypes compared with unadjuvanted vaccines; the Delta + CpG vaccine group had a higher proportion of IgG2b antibodies, indicating bias towards Th1 immunity. The proportions of IgG1 and IgG2b in the Delta + MF59-like vaccine group were similar to those of the unadjuvanted vaccine. However, the Delta + Alum vaccine group had a higher proportion of IgG1 antibodies, indicating bias towards Th2 immunity. Antigen-specific cytokine secretion CD4/8+ T cells were analyzed. In conclusion, the results of this study show differences in the immune efficacy of CpG, MF59-like, and Alum adjuvant Delta strain inactivated SARS-CoV-2 vaccines in mice, which have significant implications for the selection strategy for vaccine adjuvants.

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The main approach to preventing tick-borne encephalitis (TBE) is vaccination. Formaldehyde-inactivated TBE vaccines have a proven record of safety and efficiency but have never been characterized structurally with atomic resolution. We report a cryoelectron microscopy (cryo-EM) structure of the formaldehyde-inactivated TBE virus (TBEV) of Sofjin-Chumakov strain representing the Far-Eastern subtype. A 3.8 Å resolution reconstruction reveals the structural integrity of the envelope E proteins, specifically the E protein ectodomains. The comparative study shows a high structural similarity to the previously published structures of the TBEV European subtype strains Hypr and Kuutsalo-14. A fraction of inactivated virions exhibits asymmetric features including the deformations of the membrane profile. We propose that the heterogeneity is caused by inactivation and perform a local variability analysis on the small parts of the envelope protein shell to reveal membrane curvature features possibly induced by the inactivation. The results of this study will have implications for the design of novel vaccines against diseases caused by flaviviruses.

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The present study aimed to evaluate the effectiveness of two doses of CoronaVac in preventing SARS-CoV-2 symptomatic disease with virological confirmation, as well as in the prevention of COVID-19 moderate and severe cases. A test-negative unmatched case-control design was used, in which cases were patients with suspected COVID-19 (presenting at least two of the fol lowing symptoms: fever, chills, sore throat, headache, cough, runny nose, olfactory or taste dis orders) with virological confirmation, and controls were those whose SARS-CoV-2 test was negative. As for exposure, participants were classified as unvaccinated, or vaccinated with a complete schedule. Suspected COVID-19 cases were identified from March to November 2021, in two cities located in the State of Sao Paulo, Brazil. All participa ~ nts signed the Informed Con sent Form before enrollment. RT-PCR results and vaccination data were obtained from the local surveillance systems. Up to two phone calls were made to obtain information on the out come of the cases. A total of 2981 potential participants were screened for eligibility, of which 2163 were included, being 493 cases and 1670 controls. Vaccination, age, the reported contact with a COVID-19 suspected or confirmed case in the 14 days before symptoms onset, and the educational level were the variables independently associated with the outcome. The adjusted vaccine effectiveness for symptomatic COVID-19 (AVE) was 39.0 % (95 % CI 6.0−60.0 %). The AVE in the prevention of moderate and severe disease was 91.0 % (95 % CI 76.0−97.0 %). Our results were influenced by the waning of the Gamma variant, in the second trimester of 2021, followed by the increase in vaccination coverage, and a drop in the number of cases in the sec ond half of the year. The study demonstrated the high effectiveness of CoronaVac in prevent ing moderate/severe COVID-19 cases.

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Coronavirus disease 2019 (COVID-19) and metabolic syndrome (MetS) are currently highly prevalent diseases worldwide. Studies on clinical outcomes of patients with Omicron and MetS, especially after vaccination with an inactivated vaccine are limited. Herein, we explored the relationship between MetS and the outcome of Omicron infection. STUDY DESIGN: This was a retrospective observational study. METHODS: This study recruited 316 individuals with Omicron infection. The inpatient data from between 8 January and 7 February 2022 were obtained from designated isolation hospitals in Tianjin, China. Hierarchical and multivariable analysis was conducted on age, gender, number of complications, and vaccination status. RESULTS: Among the 316 study participants, 35.1% were diagnosed with MetS. The results showed that MetS was strongly associated with Intensive Unit Care (ICU) admission, Polymerase Chain Reaction (PCR) re-positivity, and severe COVID-19. The ICU admission rates of the unvaccinated individuals, those who received two-dose and full vaccination (3 doses), were 66.7%, 19.2%, and 0, respectively (p < 0.01). Two-dose and three-dose vaccinations significantly reduced PCR re-positivity. CONCLUSIONS: In summary, MetS increases the risk of ICU admission, PCR re-positivity, and severe COVID-19. MetS is a composite predictor of poor outcomes of Omicron infection. Two shots of inactivated vaccine, specifically three doses, effectively protect against Omicron even in the high-risk group.

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The recently prevalent variants of concerns (VOCs) of SARS-CoV-2 belong to Omicron variants which display increased transmissibility and evade from immune protection generated by vaccines and/or natural infections. Better immunization strategies should be explored to induce broader immune responses against evolving SARS-CoV-2 variants. Here, we used inactivated vaccines derived from ancestral (Wu), Delta (Del) and Omicron (Omi) strains to immunize mice with homologous booster (3 × Wu, 3 × Del and 3 × Omi) or heterologous sequential booster (Wu/Del/Omi and Omi/Wu/Del) to evaluate their responses against two pre-Omicron (Wu and Del) and four Omicron variants. Even though neutralization responses against Wu and Del variants were similar in heterologous and homologous immunization groups, heterologous immunization groups induced significantly stronger neutralizing antibody against BA.1 (4.1-11 folds higher) and BA.2 (4.7-14.2 folds higher) than those of homologous immunization groups. While homologous immunization only induced strong neutralizing responses to either pre-Omicron variants (Wu and Del) in 3 × Wu and 3 × Del groups or to Omicron variants (BA.1 and BA.2) in 3 × Omi group, heterologous immunization groups induced strong and broader neutralizing responses to both pre-Omicron (Wu, Del) and Omicron variants (BA.1 and BA.2). Homologous and heterologous immunization groups elicited similar antigen-specific T cell (IFN-γ+) and B cell responses. Compared with homologous immunization, heterologous immunization could induce stronger plasma cell responses, which have the potential to generate broader and stronger neutralizing antibodies. However, neither heterologous nor homologous immunization groups induced strong neutralizing antibody against variants with bigger genetic deviation, such as BA.4/5 or BF.7, only weak neutralizing responses were induced. Surveillance on SARS-CoV2 variants evolution and immunization strategy are needed to explore better vaccines with broader and stronger neutralizing antibodies against post pandemic COVID-19.

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Severe acute respiratory syndrome coronavirus 2 (SARS-Cov2) infection has caused an increase in mortality and morbidity, but with vaccination, the disease severity has significantly reduced. With the emergence of various variants of concern (VOCs), the vaccine breakthrough infection has also increased. Here we studied circulating spike-specific T follicular response (cTfh) in infection-naïve vaccinees and convalescent vaccinees (individuals who got the Delta breakthrough infection after two doses of BBV152 vaccine) to understand their response as they are the most crucial cells that are involved in vaccine-mediated protection by helping in B-cell maturation. Our results indicated that cTfh cells in both the groups recognized the wild-type and Delta spike protein but memory response to the wild-type spike was superior in infection-naïve than in the convalescent group. The cytokine response, particularly interleukin-21 (IL-21) from cTfh, was also higher in infection-naïve than in convalescent vaccinees, indicating a dampened cTfh response in convalescent vaccinees after breakthrough infection. Also, there was a positive correlation between IL-21 from cTfh cells and neutralizing antibodies of infection-naïve vaccinees. Multiple cytokine analysis also revealed higher inflammation in convalescent vaccinees. Our data indicated that the necessity of a third booster dose may be individual-specific depending on the steady-state functional phenotype of immune cells.

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Background/Purpose: Optimizing vaccine efficacy is of particular concern in patients undergoing hematopoietic stem cell transplantation (HSCT), which mainly have an inadequate immune response to primary SARS-CoV-2 vaccination. This investigation aimed to explore the potential prime-boost COVID-19 vaccination strategies following autologous (auto-) HSCT. Methods: In a randomized clinical trial, patients who had already received two primary doses of receptor-binding domain (RBD) tetanus toxoid (TT) conjugated SARS-CoV-2 vaccine during three to nine months after auto-HSCT were randomized to receive either a homologous RBD-TT conjugated or heterologous inactivated booster dose four weeks after the primary vaccination course. The primary outcome was comparing the anti-S IgG Immune status ratio (ISR) four weeks after the heterologous versus homologous booster dose. The assessment of safety and reactogenicity adverse events was considered as the secondary outcome. Results: Sixty-one auto-HSCT recipients were recruited and randomly assigned to receive either homologous or heterologous booster doses four weeks after the primary vaccination course. The mean ISR was 3.40 (95% CI: 2.63- 4.16) before the booster dose with a 90.0% seropositive rate. The ISR raised to 5.12 (95% CI: 4.15- 6.08) with a 100% seropositive rate after heterologous (P= 0.0064) and to 3.42 (95% CI: 2.67- 4.17) with a 93.0% seropositivity after the homologous booster doses (P= 0.96). In addition, the heterologous group suffered more AEs following the booster dosage than the homologous group, but this difference was not statistically significant (p = 0.955). In multivariable analysis, the prime-boost vaccination strategy (heterologous versus homologous), the level of ISR before the booster dose, and the length of time between auto-HSCT and booster dose were the positive predictors of serologic response to a booster dose. No serious adverse event is attributed to booster vaccination. Conclusion: In patients who were primed with two SARS-CoV-2 vaccine doses during the first year after auto-HSCT, heterologous prime-boost COVID-19 vaccination with inactivated platform resulted in considerably enhanced serologic response and non-significantly higher reactogenicity adverse events than homologous RBD-TT conjugated prime-boost COVID-19 vaccination strategy.

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Chronic liver disease (CLD) entails elevated risk of COVID-19 severity and mortality. The effectiveness of the booster dose of inactivated SARS-CoV-2 vaccine in stimulating antibody response in CLD patients is unclear. Therefore, we conducted a cross-sectional study involving 237 adult CLD patients and 170 healthy controls (HC) to analyze neutralizing antibodies (NAbs) against SARS-CoV-2 prototype and BA.4/5 variant, anti-receptor binding domain (RBD) IgG, and total anti-SARS-CoV-2 antibodies. Serum levels of the total anti-SARS-CoV-2 antibodies, anti-RBD IgG and inhibition efficacy of NAbs were significantly elevated in CLD patients after the booster dose compared with the pre-booster dose, but were relatively lower than those of HCs. Induced humoral responses decreased over time after booster vaccination. The neutralization efficiency of the serum against BA.4/5 increased but remained below the inhibition threshold. All four SARS-CoV-2 antibodies, including total anti-SARS-CoV-2 antibodies, anti-RBD IgG and NAbs against prototype and BA.4/5, were lower in patients with severe CLD than those with non-severe CLD. After booster shot, age and time after the last vaccine were the risk factors for seropositivity of NAb against BA.4/5 in CLD patients. Additionally, white blood cell counts and hepatitis B core antibodies were the protective factors, and severe liver disease was the risk factor associated with seropositivity of total anti-SARS-CoV-2 antibodies. Overall, our data uncovered that antibody responses were improved in CLD patients and peaked at 120 days after the booster vaccines. All antibodies excepting total anti-SARS-CoV-2 antibodies declined after peak. CLD patients exhibited impaired immunologic responses to vaccination and weakened NAbs against BA.4/5, which hindered the protective effect of the booster shot against Omicron prevalence. Cellular immune responses should be further evaluated to determine the optimal vaccine regimen for CLD patients.

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This prospective cohort study aimed to evaluate the safety of an inactivated coronavirus disease 2019 (COVID-19) vaccine in pregnant women at a tertiary hospital in Hubei, China. Pregnancy outcomes were compared between pregnant vaccinated and unvaccinated women. Composite adverse pregnancy outcomes were defined as one or more of maternal adverse outcomes (prenatal pyrexia, postpartum hemorrhage, maternal intensive care unit admission, and a prethrombotic state) and adverse neonatal outcomes (premature delivery, intrauterine fetal death or induction of labor, fetal macrosomia, fetal growth restriction, small-for-gestational age, fetal abnormalities, neonatal admission to the neonatal intensive care unit, and birth asphyxia). Of a total of 845 participants in the delivery cohort, 41.2% (348/845) received at least one dose of the COVID-19 vaccination, and 33.6% (284/845) received two doses. In total, 25.3% (88/348) of the vaccinated group were vaccinated at 0-4 weeks of pregnancy. No significant difference was found in the composite adverse outcomes between the vaccinated and unvaccinated participants, regardless of whether vaccination occurred before (44/243 [18.1%] vs. 71/497 [14.3%]; P = .17) or during early pregnancy (14/105 [13.3%] vs. 71/497[14.3%]; P = .79). These findings indicate that the pregnancy outcomes of women who received the COVID-19 vaccination, even if they were vaccinated early in pregnancy, were comparable to those of unvaccinated women. This study was registered with the Chinese Clinical Trial Center (ChiCTR2100051756).

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BACKGROUND: It is important to understand the dynamics of SARS-CoV-2 transmission in close-contact settings such as households. We hypothesized that children would most often acquire SARS-CoV-2 from a symptomatic adult caregiver. METHODS: This prospective cohort study was conducted from April 2020 to July 2022 in a low-resource, urban settlement in Brazil. We recruited families who brought their children to a public clinic. We collected nasopharyngeal and oral swabs from household members and tracked symptoms and vaccination. RESULTS: In total, 1256 participants in 298 households were tested for SARS-CoV-2. A total of 4073 RT-PCR tests were run with 893 SARS-CoV-2 positive results (21.9%). SARS-CoV-2 cases were defined as isolated cases (N = 158) or well-defined transmission events (N = 175). The risk of household transmission was lower if the index case was a child (OR: 0.3 [95% CI: 0.16-0.55], P < .001) or was vaccinated (OR: 0.29 [95% CI: 0.1-0.85], P = .024), and higher if the index was symptomatic (OR: 2.53 [95% CI: 1.51-4.26], P < .001). The secondary attack rate for child index cases to child contacts was 0.29, whereas the secondary attack rate for adult index cases to child contacts was 0.47 (P = .08). CONCLUSIONS: In this community, children were significantly less infectious to their household contacts than adolescents or adults. Most children were infected by a symptomatic adult, usually their mother. There was a double benefit of vaccination as it protected the vaccine from severe illness and prevented onward transmission to household contacts. Our findings may also be valid for similar populations throughout Latin America.

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Background: Inactivated, whole-virion vaccines have been used extensively in the SARS-CoV-2 pandemic. Its efficacy and effectiveness across regions have not been systematically evaluated. Efficacy refers to how well a vaccine performs in a controlled environment. Effectiveness refers to how well it performs in real world settings. Methods: This systematic review and meta-analysis reviewed published, peer-reviewed evidence on all WHO-approved inactivated vaccines and evaluated their efficacy and effectiveness against SARS-CoV-2 infection, symptomatic infection, severe clinical outcomes, and severe COVID-19. We searched Pubmed (including MEDLINE), EMBASE (via OVID), Web of Science Core Collection, Web of Science Chinese Science Citation Database, and Clinicaltrials.gov. Findings: The final pool included 28 studies representing over 32 million individuals reporting efficacy or effectiveness estimates of complete vaccination using any approved inactivated vaccine between January 1, 2019 and June 27, 2022. Evidence was found for efficacy and effectiveness against symptomatic infection (OR 0.21, 95% CI 0.16-0.27, I2 = 28% and OR 0.32, 95% CI 0.16-0.64, I2 = 98%, respectively) and infection (OR 0.53, 95% CI 0.49-0.57, I2 = 90% and OR 0.31, 95% CI 0.24-0.41, I2 = 0%, respectively) for early SARS-CoV-2 variants of concern (VoCs) (Alpha, Delta), and for waning of vaccine effectiveness with more recent VoCs (Gamma, Omicron). Effectiveness remained robust against COVID-related ICU admission (OR 0.21, 95% CI 0.04-1.08, I2 = 99%) and death (OR 0.08, 95% CI 0.00-2.02, I2 = 96%), although effectiveness estimates against hospitalization (OR 0.44, 95% CI 0.37-0.53, I2 = 0%) were inconsistent. Interpretation: This study showed evidence of efficacy and effectiveness of inactivated vaccines for all outcomes, although inconsistent reporting of key study parameters, high heterogeneity of observational studies, and the small number of studies of particular designs for most outcomes undermined the reliability of the findings. Findings highlight the need for additional research to address these limitations so that more definitive conclusions can be drawn to inform SARS-CoV-2 vaccine development and vaccination policies. Funding: Health and Medical Research Fund on COVID-19, Health Bureau of the Government of the Hong Kong SAR.

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The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been widespread globally, and vaccination is critical for preventing further spread or resurgence of the outbreak. Inactivated vaccines made from whole inactivated SARS-CoV-2 virus particles generated in Vero cells are currently the most widely used COVID-19 vaccines, with China being the largest producer of inactivated vaccines. As a result, the focus of this review is on inactivated vaccines, with a multidimensional analysis of the development process, platforms, safety, and efficacy in special populations. Overall, inactivated vaccines are a safe option, and we hope that the review will serve as a foundation for further development of COVID-19 vaccines, thus strengthening the defense against the pandemic caused by SARS-CoV-2.

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BACKGROUND: Negative conversion of nucleic acid was a key factor in deciding discharge or the end of isolation of asymptomatic or mild COVID-19 patients. We aimed to explore the effect of vaccination on the time to negative conversion after Omicron infection. METHODS: This retrospective cohort study included asymptomatic or mild patients with COVID-19 admitted to Fangcang shelter Hospital from November 10, 2022 to December 2, 2022. The relationship between vaccination status and the time to negative conversion was analyzed by multiple linear regression. RESULTS: A total of 2,104 asymptomatic or mild COVID-19 patients were included in the analysis, of whom 1,963 were vaccinated. The mean time to negative conversion of no vaccination, one dose, two doses, and three doses were 12.57 (5.05), 12.18 (3.46), 11.67 (4.86) and 11.22 (4.02) days, respectively (p = 0.002). Compared with no vaccination, two doses (ß=-0.88, 95% CI: -1.74, -0.02, p = 0.045), and three doses (ß=-1.51, 95% CI: -2.33, -0.70, p < 0.001) were both associated with shorter time to negative conversion. Comparing with two doses, booster dose was associated significantly with shorter time to negative conversion (ß=-0.63, 95% CI: -1.07, -0.20, p = 0.004). Age was positively correlated with the time to negative conversion (ß = 0.04, 95% CI: 0.02, 0.05, p < 0.001). CONCLUSION: Vaccination with inactivated vaccine and booster dose can shorten the time to negative conversion of asymptomatic or mild COVID-19 patients. The significant prolongation of time to negative conversion with increasing age suggests the promotion of vaccination, especially booster dose, particularly in the elderly.

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