The booster immunization using commercial vaccines effectively protect chickens against novel variants of infectious bursal disease virus (genotype A2dB1)

The novel variant IBDV (nVarIBDV, genotype A2dB1), characterized by bursal atrophy of fabricius and decreased lymphocytes, has been emerging on a large scale in Asia (including China) since late 2018. nVarIBDV is a new threat to the poultry industry, yet the currently licensed commercial vaccines, including the live viral vector vaccine, IBDV immune complex vaccine or VP2 subunit vaccine, are ineffective against nVarIBDV infection. In this study, specific-pathogen-free (SPF) chickens and broilers divided into 3 groups were vaccinated with the live viral vector vaccine, the VP2 subunit vaccine or the IBDV immune complex vaccine at 1 day-old, respectively. The SPF chickens received a secondary vaccination with the live B87 strain vaccine at 11-day-old. The bursa/body weight ratio, histopathology lesion of the bursa, and the differentiation between infected and vaccinated animals (DIVA) by qRT-PCR confirmed that the live viral vector vaccine or immune complex vaccine plus live B87 strain booster could provide at least 80% protection against the FJ2019-01 strain of nVarIBDV in SPF chickens. The broilers also received a secondary vaccination using a live W2512 G-61 strain vaccine at 14-day-old, and analyses showed that the VP2 subunit vaccine or immune complex vaccine plus the live W2512 G-61 strain booster also provided more than 80% protection against the FJ2019-01 strain of nVarIBDV. Unfortunately, the live viral vector vaccine plus live W2512 G-61 strain booster provided poor to moderate protection against FJ2019-01 in broilers. These findings suggest that combining commercial vaccines with rational booster immunization can effectively protect chickens against an nVarIBDV challenge.

Quantitative Analysis of the Instant and Persistent Inhibition Effects of Maternal Poliovirus Antibodies on the Immune Response in a Phase IV Trial of a Sabin Strain-Based Inactivated Poliovirus Vaccine

BACKGROUND

An inactivated poliomyelitis vaccine made from Sabin strains (sIPVs) has widely been used in China since 2015. However, the quantitative data on the instant and persistent inhibition effects of maternal poliovirus antibodies on the immune response to sIPV priming and booster vaccination have not been available yet.

OBJECTIVE

In this study, we aim to explore and quantify the instant and persistent inhibition effect of maternal poliovirus antibodies on the immune response elicited by sIPV primary and booster vaccination.

METHODS

The immunogenicity data consisting of the days 0 and 30 after the prime and booster vaccination of the sIPV in a phase IV trial were pooled for a quantitative analysis of the inhibition effect of maternal poliovirus antibody. The geometric mean ratio (GMR) was calculated using linear regression models, representing that every 2-fold higher maternal poliovirus antibody titer may result in a (1-GMR) lower postimmunization antibody titer.

RESULTS

The GMRs for poliovirus types 1, 2, and 3 were 0.79 (0.77-0.82), 0.85 (0.81-0.89), and 0.87 (0.83-0.91) at 30 days after the priming series, 0.86 (0.83-0.89), 0.81 (0.76-0.85), and 0.86 (0.80-0.93) at one year after the priming series, and 0.96 (0.94-0.99), 0.89 (0.86-0.93), and 0.98 (0.93-1.03) at 30 days after the booster dose. The inhibition effect continued to exist until the booster dose 1 year later, and such a persistent inhibition effect was almost attenuated for poliovirus types 1 and 3, and partly reduced for type 2 at 30 days after the booster dose.

CONCLUSION

A wider interval between the four sIPV doses might be a consideration for reducing the effect of maternal antibodies and subsequently eliciting and maintaining higher antibody levels to protect against poliovirus transmission and infection at the final stage of polio eradication in the global world. This study's clinical trial registry number is NCT04224519.

Relative effectiveness of bivalent COVID-19 vaccine: a systematic review and meta-analysis

Objective

The rapid development of COVID-19 bivalent vaccines (BVs) has encompassed both the original virus strains and the variant strain. However, the effectiveness of BVs is largely unknown. Therefore, we conducted a systematic review and meta-analysis of the effectiveness of BVs.

Methods

Literature research was conducted through PubMed, Cochrane Library, Embase, and Web of Science up until November 4, 2023. Both randomized control trials and observational studies were considered for inclusion. Pooled estimates were calculated using a random effects model. The Newcastle-Ottawa Scale (NOS) was used to assess the risk of bias in cohort and case-control studies.

Results

A total of 1,174 articles were reviewed and 22 eligible studies were included. All included studies were observational (15 cohort studies, 7 case-control studies). The total number of participants was 39,673,160, and the number of people vaccinated with BVs as an intervention group was 11,585,182. Two mRNA BVs were mainly involved, including the ancestral strain and the BA.1 or BA.4-5 variants. Meta-analysis results showed, compared with the monovalent vaccines (MVs), the relative effectiveness (rVE) of the BVs in COVID-19-associated infections/symptomatic infections, illnesses, hospitalizations, and deaths was 30.90% [95% confidence interval (CI), 8.43-53.37], 39.83% (95% CI, 27.34-52.32), 59.70% (95% CI, 44.08-75.32), and 72.23% (95% CI, 62.08-82.38), respectively. For those aged 50 years and older, BVs provided an additional 49.69% (95% CI, 41.44-57.94) effective protection compared with MVs. During the dominance period of the omicron XBB variant strain, BVs provided an additional 47.63% (95% CI, 27.45-67.82) effective protection compared with MVs.

Conclusion

Our findings show that the rVE of BVs in preventing COVID-19-associated infections, symptomatic infections, illnesses, hospitalizations, and deaths is higher compared to MVs. Particularly for people over 50 years of age and during the Omicron variant XBB dominance phase, BVs provided superior protection. Therefore, BVs may have a broader application in the prevention and control of coronaviruses variant.

Immune Persistence following Primary Immunization and the Immunogenicity and Safety of a Booster Dose of a Multidose Sabin Strain-Based Inactivated Polio Vaccine in Infants Aged 18 Months

BACKGROUND

The multidose Sabin-strain inactivated poliovirus vaccine (sIPV) has the potential to significantly aid in the eradication of poliomyelitis, particularly in low- and middle-income countries. As part of a phase III clinical trial in which infants were given three doses of primary immunization at 2, 3, and 4 months of age, this study aimed to evaluate immune persistence following primary immunization, as well as the safety and immunogenicity of a booster of the 5-dose sIPV in infants aged 18 months.

METHODS

Infants aged 18 months were given one booster dose of 5-dose sIPV in stage one, which was open-label. Unblinding was performed for stage two after completing primary immunization, which was randomized, blinded, and controlled; infants aged 18 months in the test group I-III, IPV group, and single-dose sIPV group were given one booster dose of 5-dose sIPV, conventional IPV, and single-dose sIPV, respectively, in stage two.

RESULTS

This study included 1438 infants in the immune persistence and safety set and 1387 infants in the booster per-protocol set. Fourteen months after primary immunization, the seropositivity rates (≥1:8) for types 1-3 were 100%, 99.88%, and 99.53% in the 5-dose sIPV groups; 100%, 98.97%, and 97.23% in the IPV group; and 99.66%, 100%, and 99.66% in the single-dose sIPV group. A total of 30 days after booster immunization, the seropositivity rates (≥1:8) of 3 serotypes in all the groups reached 100%. The geometric mean titers of neutralizing antibodies for types 1-3 in the 5-dose sIPV group were 9962.89, 10273, and 7870.21, with geometric mean increases of 15.76, 33.15, and 24.5, compared to the pre-booster level. The overall incidence of adverse reactions was 8.97%, with fever being the most common, observed at rates of 7.1%, 5.52%, and 7.96% in the 5-dose sIPV, IPV, and single-dose groups, respectively (p = 0.4845).

CONCLUSIONS

The 5-dose sIPV has shown promising immune persistence and robust immune response following a booster immunization, coupled with an acceptable safety profile.

Rational prediction of immunogenicity clustering through cross-reactivity analysis of thirteen SARS-CoV-2 variants

SARS-CoV-2 breakthrough infections in vaccinated individuals underscore the threat posed by continuous mutating variants, such as Omicron, to vaccine-induced immunity. This necessitates the search for broad-spectrum immunogens capable of countering infections from such variants. This study evaluates the immunogenicity relationship among SARS-CoV-2 variants, from D614G to XBB, through Guinea pig vaccination, covering D614G, Alpha, Beta, Gamma, Delta, BA.1, BA.2, BA.2.75, BA.2.75.2, BA.5, BF.7, BQ.1.1, and XBB, employing three immunization strategies: three-dose monovalent immunogens, three-dose bivalent immunogens, and a two-dose vaccination with D614G followed by a booster immunization with a variant strain immunogen. Three distinct immunogenicity clusters were identified: D614G, Alpha, Beta, Gamma, and Delta as cluster 1, BA.1, BA.2, and BA.2.75 as cluster 2, BA.2.75.2, BA.5, BF.7, BQ.1.1, and XBB as cluster 3. Broad-spectrum protection could be achieved through a combined immunization strategy using bivalent immunogens or D614G and XBB, or two initial D614G vaccinations followed by two XBB boosters. A comparison of neutralizing antibody levels induced by XBB boosting and equivalent dosing of D614G and XBB revealed that the XBB booster produced higher antibody levels. The study suggests that vaccine antigen selection should focus on the antigenic alterations among variants, eliminating the need for updating vaccine components for each variant.

Vaccine-induced immune thrombotic thrombocytopenia post COVID-19 booster vaccination in Brazil: a case series

Background

The emergence of new variants of SARS-CoV-2 has led to the administration of different booster vaccines to mitigate COVID-19. Vaccines with adenoviral vectors have been rarely associated with vaccine-induced immune thrombotic thrombocytopenia (VITT).

Objectives

This study aimed to describe 15 cases of VITT after the third and fourth doses of the COVID-19 vaccine in Brazil.

Methods

Cases were reported after all kinds of anti-SARS-CoV-2 booster vaccinations between October 17, 2021, and September 4, 2022.

Results

Of the 26 suspected cases, 15 cases of VITT were analyzed. Of these, 10 were classified as definite VITT, 2 as probable, 1 as possible, and 2 as unlikely. The estimated frequency of definite, probable, or possible VITT was 0.33 cases per million. Cases were assigned to ChAdOx1 (13 cases), Ad26.COV2.S (1 case), and BNT162b2 (1 case). None of the patients received an adenoviral vaccine as a primary vaccination. The average age of participants was 34 years, and symptoms usually appeared 8 days after vaccination. Headache was the most common symptom, and cerebral veins were the most affected thrombotic site. The overall mortality risk was 53%. Anti-platelet factor 4 enzyme-linked immunosorbent assay serology was positive in 11 out of 15 patients (73.3%), negative in 2 (13.3%), and missing in 2 (13.3%).

Conclusion

The study confirms that VITT is linked to the first exposure to adenoviral vector vaccines. Since January 2023, Brazil has recommended preferably COVID-19 messenger RNA vaccines for individuals aged 18 to 39 years. We suggest that, in the current disease scenario, COVID-19 adenovirus vaccines should not be the first choice for individuals aged <50 years who have not received a previous dose of this type of vaccine.

Field investigation of high reported non-neonatal tetanus burden in Uganda, 2016-2017

BACKGROUND

Despite providing tetanus-toxoid-containing vaccine (TTCV) to infants and reproductive-age women, Uganda reports one of the highest incidences of non-neonatal tetanus (non-NT). Prompted by unusual epidemiologic trends among reported non-NT cases, we conducted a retrospective record review to see whether these data reflected true disease burden.

METHODS

We analysed nationally reported non-NT cases during 2012-2017. We visited 26 facilities (14 hospitals, 12 health centres) reporting high numbers of non-NT cases (n = 20) or zero cases (n = 6). We identified non-NT cases in facility registers during 1 January 2016-30 June 2017; the identified case records were abstracted.

RESULTS

During 2012-2017, a total of 24 518 non-NT cases were reported and 74% were ≥5 years old. The average annual incidence was 3.43 per 100 000 population based on inpatient admissions. Among 482 non-NT inpatient cases reported during 1 January 2016-30 June 2017 from hospitals visited, 342 (71%) were identified in facility registers, despite missing register data (21%). Males comprised 283 (83%) of identified cases and 60% were ≥15 years old. Of 145 cases with detailed records, 134 (92%) were clinically confirmed tetanus; among these, the case-fatality ratio (CFR) was 54%. Fourteen cases were identified at two hospitals reporting zero cases. Among >4000 outpatient cases reported from health centres visited, only 3 cases were identified; the remainder were data errors.

CONCLUSIONS

A substantial number of non-NT cases and deaths occur in Uganda. The high CFR and high non-NT burden among men and older children indicate the need for TTCV booster doses across the life course to all individuals as well as improved coverage with the TTCV primary series. The observed data errors indicate the need for data quality improvement activities.

Antigen presentation dynamics shape the antibody response to variants like SARS-CoV-2 Omicron after multiple vaccinations with the original strain

The Omicron variant of SARS-CoV-2 is not effectively neutralized by most antibodies elicited by two doses of mRNA vaccines, but a third dose increases anti-Omicron neutralizing antibodies. We reveal mechanisms underlying this observation by combining computational modeling with data from vaccinated humans. After the first dose, limited antigen availability in germinal centers (GCs) results in a response dominated by B cells that target immunodominant epitopes that are mutated in an Omicron-like variant. After the second dose, these memory cells expand and differentiate into plasma cells that secrete antibodies that are thus ineffective for such variants. However, these pre-existing antigen-specific antibodies transport antigen efficiently to secondary GCs. They also partially mask immunodominant epitopes. Enhanced antigen availability and epitope masking in secondary GCs together result in generation of memory B cells that target subdominant epitopes that are less mutated in Omicron. The third dose expands these cells and boosts anti-variant neutralizing antibodies.

Viral load dynamics in SARS-CoV-2 Omicron breakthrough infections

In order to determine viral dynamics in Omicron breakthrough infections, we measured SARS-CoV-2 RNA in 206 double vaccinated or boostered individuals. During the first three days following the onset of symptoms, viral loads were significantly higher (Ct 21.76) in vaccinated compared to boostered (Ct 23.14) individuals (p = 0.029). However, by performing a longitudinal analysis on 32 individuals over 14 days, no difference in the viral load trajectory was observed between double vaccinated and boostered patients. Our results indicate that booster immunization results in a small reduction in detectable viral loads without significantly changing viral load dynamics over time.

The humoral response of mRNA COVID-19 vaccine in hematological diseases: the HEMVACO study

Objectives

The HEMVACO study evaluated the humoral response after mRNA anti-SARS-CoV-2 vaccination in an hematological cohort.

Methods

HEMVACO was a prospective, multicentric study registered in ClinicalTrials.gov, number NCT04852796. Patients received two or three doses of BNT162b2 vaccine or mRNA-1273 vaccine. The SARS-CoV-2 TrimericS IgG titers were measured 1, 3, 6 and 12 months after the second dose.

Results

Only 16 patients (11.6%) were naive of hematological treatment and 77 patients (55.8%) were on active treatment for hemopathy. Among the 138 analyzed patients, positive antibody titer at 1 month was obtained in 68.1% of patients with mean serology at 850±883 BAU/ml. Risk factors for vaccine failure were anti-CD20 therapy (OR = 111[14.3-873]; P < 0.001), hypogammaglobulinemia under 8 g/L (OR = 2.49[1.05-5.92]; P = 0.032) and lymphopenia under 1.5G/L (OR = 2.47[1.18-5.17]; P = 0.015). Anti-CD20 therapy induced no anti-SARS-CoV-2 seroconversion (96%). Seventy-eight patients (56.5%) received a third dose and could reach the SARS-CoV-2 TrimericS IgG titer of high-risk patients (P = 0.54). The median titer at 379 BAU/ml distinguished two groups of vaccine response (99±121 BAU/ml versus 1,109±678 BAU/ml).

Conclusion

Vaccination should be performed before anti-CD20 therapy if the hemopathy treatment can be delayed. Administration of the third vaccine dose was interesting for patients with suboptimal response, defined by a 379 BAU/ml titer in our study.

Early assessment of the safety and immunogenicity of a third dose (booster) of COVID-19 immunization in Chinese adults

Inducing durable and effective immunity against severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) via vaccination is essential to combat the current pandemic of coronavirus disease 2019 (COVID-19). It has been noticed that the strength of anti-COVID-19 vaccination-induced immunity fades over time, which calls for an additional vaccination regime, as known as booster immunization, to restore immunity among previously vaccinated populations. Here we report a pilot open-label trial of a third dose of BBIBP-CorV, an inactivated SARS-CoV-2 vaccine (Vero cell), on 136 participants aged between 18 to 63 years. Safety and immunogenicity in terms of neutralizing antibody titers and cytokine/chemokine responses were analyzed as the main endpoint until day 28. While systemic reactogenicity was either absent or mild, SARS-CoV-2-specific neutralizing antibody titers rapidly arose in all participants within 4 weeks, surpassing the peak antibody titers elicited by the initial two-dose immunization regime. Broad increases of cellular immunity-associated cytokines and chemokines were also detected in the majority of participants after the third vaccination. Furthermore, in an exploratory study, a newly developed recombinant protein vaccine, NVSI-06-08 (CHO Cells), was found to be safe and even more effective than BBIBP-CorV in eliciting humoral immune responses in BBIBP-CorV-primed individuals. Together, these results indicate that a third immunization schedule with either homologous or heterologous vaccine showed favorable safety profiles and restored potent SARS-CoV-2-specific immunity, providing support for further trials of booster vaccination in larger populations.

COVID-19 Vaccine Booster Hesitancy (VBH) of Healthcare Workers in Czechia: National Cross-Sectional Study

The emerging SARS-CoV-2 variants and waning vaccine-elicited immunity are two public health challenges that occurred simultaneously and synergistically during the summer of 2021 and led to a surging demand for COVID-19 vaccine booster dose (BD) rollout. This study aimed to evaluate the COVID-19 vaccine booster hesitancy (VBH) among Czech healthcare workers to explore the potential determinants of VBH. A national cross-sectional survey-based study was carried out between 3 and 11 November 2021, using an online self-administered questionnaire (SAQ) that explored the participants' demographic characteristics, COVID-19 infection and vaccine anamneses, willingness to receive COVID-19 vaccine BD, and the psychosocial drivers of VBH. A total of 3454 HCW properly responded to the online SAQ, of which 80.9% were females, 30.3% were medical professionals, and 50.5% were ≤47 years old. Most of the participants were already inoculated against SARS-CoV-2 (95.2%), and BTN162b2 was the most commonly administered vaccine (90.7%). As the study sample was planned to represent the target population, it revealed a high level of BD acceptance (71.3%) among Czech HCW, while 12.2% were still hesitant and 16.6% were against the currently available BD. These results are consistent with other recent results from central Europe. Medical professional, male, and older participants were more likely to accept BD rather than allied health professional, female, and younger participants. The BDs' perceived effectiveness against severe illness, symptomatic infection, and community transmission was a significant and strong predictor for BD acceptance, while the effectiveness against the circulating variants was not that important for our target population. The BDs' perceived safety and ethical dilemmas of vaccine justice should be addressed sufficiently while communicating with HCW and other population groups. The altruistic reasons for BD acceptance, i.e., family protection, patient protection, and community health protection, underpin the recommendation of postponing the COVID-19 vaccine mandating in favour of stressing these altruistic concerns amid public health messaging.

Systematic Booster after Rabies Pre-Exposure Prophylaxis to Alleviate Rabies Antibody Monitoring in Individuals at Risk of Occupational Exposure

Pre-exposure rabies prophylaxis (PrEP) is recommended for people at frequent or increased risk of professional exposure to lyssavirus (including rabies virus). PrEP provides protection against unrecognized exposure. After the primary vaccination, one's immune response against rabies may decline over time. We aimed to evaluate the immune response to rabies in individuals immunized for occupational reasons before and after a booster dose of the rabies vaccine. With this aim, we retrospectively documented factors associated with an inadequate response in individuals vaccinated for occupational purposes. Our findings analyzed data from 498 vaccinated individuals and found that 17.2% of participants had an inadequate antibody titration documented after their primary vaccination without the booster, while inadequate response after an additional booster of the vaccine was evidenced in 0.5% of tested participants. This study showed that a single booster dose of vaccine after PrEP conferred a high and long-term immune response in nearly all individuals except for rare, low responders. A systematic rabies booster after primary vaccination may result in alleviating the monitoring strategy of post-PrEP antibody titers among exposed professionals.

Long-term memory response after a single intramuscular rabies booster vaccination, 10-24 years after primary immunization

BACKGROUND

To date, published data regarding long-lasting immunological rabies memory after a pre-exposure prophylaxis (PrEP)-schedule are scarce. We tested the hypothesis that rabies booster immunization elicits rapid anamnestic responses.

METHODS

For this observational study, we included participants who had received PrEP 10-24 years before inclusion. We measured rabies antibody titers before, and on days 3, 7 and 14 after one single intramuscular booster.

RESULTS

All 28 participants responded adequately regardless route of administration or (2-dose vs. 3-dose) PrEP-regimen.

CONCLUSION

Rabies immunological memory is reactivated within 7 days after a single intramuscular booster immunization, even when administered 10-24 years after PrEP.

Memory immune response and safety of a booster dose of Japanese encephalitis chimeric virus vaccine (JE-CV) in JE-CV-primed children

Japanese encephalitis chimeric virus vaccine (JE-CV) is a licensed vaccine indicated in a single dose administration for primary immunization. This controlled phase III comparative trial enrolled children aged 36-42 mo in the Philippines. 345 children who had received one dose of JE-CV in a study two years earlier, received a JE-CV booster dose. 105 JE-vaccine-naïve children in general good health were randomized to receive JE-CV (JE-vaccine naïve group; 46 children) or varicella vaccine (safety control group; 59 children). JE neutralizing antibody titers were assessed using PRNT50. Immunological memory was observed in children who had received the primary dose of JE-CV before. Seven days after the JE-CV booster dose administration, 96.2% and 66.8% of children were seroprotected and had seroconverted, respectively, and the geometric mean titer (GMT) was 231 1/dil. Twenty-eight days after the JE-CV booster dose seroprotection and seroconversion were achieved in 100% and 95.3% of children, respectively, and the GMT was 2,242 1/dil. In contrast, only 15.4% of JE-CV-vaccine naïve children who had not received any prior JE vaccine were seroprotected seven days after they received JE-CV. One year after receiving the JE-CV booster dose, 99.4% of children remained seroprotected. We conclude that JE-CV is effective and safe, both as a single dose and when administrated as a booster dose. A booster dose increases the peak GMT above the peak level reached after primary immunization and the antibody persistence is maintained at least one year after the JE-CV booster dose administration. Five year follow up is ongoing.

The augmentation of tumor-specific immunity using haptenic muramyl dipeptide (MDP) derivatives. III. Eradication of disseminated murine chronic leukemia cells by utilizing MDP hapten-reactive helper T-cell activity

A previous paper has demonstrated that enhanced tumor-specific immunity could be induced by priming mice with Bacillus Calmette Guerin (BCG) and subsequently immunizing them with syngeneic tumor cells modified with BCG-cross-reactive muramyl dipeptide (MDP) hapten. The present study establishes a tumor-specific immunotherapy protocol for a murine chronic leukemia based on the above T-T cell collaboration between antitumor effector T cells and anti-MDP hapten helper T cells induced by BCG priming. BALB/c mice which had been primed to BCG were injected intravenously (i.v.) with viable, syngeneic BCL1 leukemia cells. One week later, these mice were immunized intraperitoneally (i.p.) with unmodified or MDP hapten-modified, 10,000 R X-irradiated BCL1 cells, followed by 4 booster immunizations at 5-day intervals. The administration of unmodified BCL1 tumor cells into BCG-primed mice failed to prevent them from tumor death due to the persistent growth of preinjected BCL1 cells. In contrast, the immunization of BCG-primed, BCL1 leukemia-cell-bearing mice with MDP-modified BCL1 cells resulted in a high growth inhibition of leukemia cells and protection of these mice from death by leukemia. It was also revealed that potent tumor-specific, T-cell-mediated immunity was generated in mice which survived in this immunotherapy model. Thus, these results indicate that administration of MDP hapten-modified, syngeneic leukemia cells into leukemia-bearing mice which have been primed with BCG results in potent tumor-specific, T-cell-mediated immunity attributable to preventing the growth of disseminated leukemic cells.