OBJECTIVE: Vaccine hesitancy has been a public health issue for some time now, but gained more attention during COVID-19 pandemic. This systematic review aimed to estimate the prevalence of COVID-19 vaccination hesitancy and identify factors affecting it among adolescents. MATERIALS AND METHODS: The preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P 2020) was used. A search was performed in PubMed/ MEDLINE, EMBASE, Google Scholar, Herdin, and Cochrane databases on September 2023 using the key words: (COVID-19 OR SARS-COV OR corona virus) AND (Vaccination OR immunization) AND (adolescence OR teenagers OR youth) AND (hesitancy OR acceptance). Observational studies which determined the prevalence or risk factors for COVID-19 vaccine hesitancy among adolescents aged 10-19 years old were included. RESULTS: There were 5 good quality cross-sectional studies included. The prevalence of adolescents who did not want to be vaccinated ranged between 8.4% and 61.0%; while the prevalence of being unsure if they want to be vaccinated was between 31.6% and 88.0%. Factors associated with vaccine hesitancy included being economically disadvantaged, not having influenza vaccination, worrying about its effectiveness and safety, and low perceived necessity. CONCLUSION There is good quality evidence that COVID-19 vaccine hesitancy exists among adolescents. It is recommended that health workers should conduct information and education campaigns to iterate the effectiveness, safety, and misconceptions about of COVID-19 vaccination. Vaccination programs should also reach out to economically disadvantaged adolescents, and tapping parents and social media may be an effective strategy to improve vaccination acceptance among adolescents.
COVID-19 ; SARS-COV ; Severe acute respiratory syndrome-related coronavirus ; Vaccination ; Immunization ; Adolescent ; Adolescence ; Teenagers ; Youth

This study followed up the immune memory after 3-dose revaccination among infants with non-and low-response following primary hepatitis B (HepB) vaccination. About 120 children without self-booster doses were finally included who had anti-HBs<10 mIU/ml (anti-HBs negative) at the time of follow-up, of whom 86 children completed blood sampling and anti-HBs testing. Before the challenge dose, all 86 children were negative for anti-HBs, and the GMC of anti-HBs was<10 mIU/ml. The seropositive conversion rate of anti-HBs was 100% and the GMC of anti-HBs was 886.11 (95%CI: 678.15-1 157.84) mIU/ml after the challenge dose. Compared with those with GMC<7 mIU/ml before the challenge dose, infants with GMC>7 mIU/ml had a higher anti-HBs level after the challenge dose. The β value (95%CI) was 0.82 (0.18-1.46) (P=0.012). Compared with those with GMC<1 000 mIU/ml at primary vaccination, infants with GMC≥1 000 mIU/ml had a higher anti-HBs level after the challenge dose. The β value (95%CI) was 0.78 (0.18-1.38)(P=0.012). The results showed a stronger immune memory was found at 9 years after revaccination among infants with non-and low-response to HepB.
Child ; Humans ; Infant ; Hepatitis B Vaccines ; Immunization, Secondary ; Hepatitis B Surface Antigens ; Immunologic Memory ; Follow-Up Studies ; Vaccination ; Hepatitis B/prevention & control* ; Hepatitis B Antibodies

Persistent infection of high-risk human papillomavirus (HPV) is the leading cause of cervical cancer. In order to achieve the goal of cervical cancer elimination, the World Health Organization (WHO) proposed the "90-70-90" goal, one of which is "90% of girls fully vaccinated with HPV vaccine by age 15 years". Based on the epidemiological characteristics of HPV infection and the characteristics of HPV vaccine, it is important to give priority to female adolescents to be vaccinated with HPV vaccine. CAV Affiliated Association for Standardized Management and Practice of Immunization Program organized an expert group to develop an expert consensus on the immunization strategy and practice of human papillomavirus vaccine for female adolescents in the Yangtze River Delta region. This consensus introduces HPV infection and related disease burden, safety, efficacy and effectiveness of HPV vaccination for female adolescents, factors affecting the health benefits of HPV vaccination for female adolescents, current HPV vaccination strategies for female adolescents, the expert advice, common problems and precautions in the Yangtze River Delta region. This consensus is developed to guide HPV vaccination for female adolescents in the Yangtze River Delta region and provide reference for other regions.
Female ; Adolescent ; Humans ; Papillomavirus Vaccines ; Papillomavirus Infections/prevention & control* ; Human Papillomavirus Viruses ; Uterine Cervical Neoplasms/prevention & control* ; Consensus ; Vaccination ; Immunization Programs

BACKGROUND: Data on the immunogenicity and safety of heterologous immunization schedules are inconsistent. This study aimed to evaluate the immunogenicity and safety of homologous and heterologous immunization schedules. METHODS: Multiple databases with relevant studies were searched with an end date of October 31, 2021, and a website including a series of Coronavirus disease 2019 studies was examined for studies before March 31, 2022. Randomized controlled trials (RCTs) that compared different heterologous and homologous regimens among adults that reported immunogenicity and safety outcomes were reviewed. Primary outcomes included neutralizing antibodies against the original strain and serious adverse events (SAEs). A network meta-analysis (NMA) was conducted using a random-effects model. RESULTS: In all, 11 RCTs were included in the systematic review, and nine were ultimately included in the NMA. Among participants who received two doses of CoronaVac, another dose of mRNA or a non-replicating viral vector vaccine resulted in a significantly higher level of neutralizing antibody than a third CoronaVac 600 sino unit (SU); a dose of BNT162b2 induced the highest geometric mean ratio (GMR) of 15.24, 95% confidence interval [CI]: 9.53-24.39. Following one dose of BNT162b2 vaccination, a dose of mRNA-1273 generated a significantly higher level of neutralizing antibody than BNT162b2 alone (GMR = 1.32; 95% CI: 1.06-1.64), NVX-CoV2373 (GMR = 1.60; 95% CI: 1.16-2.21), or ChAdOx1 (GMR = 1.80; 95% CI: 1.25-2.59). Following one dose of ChAdOx1, a dose of mRNA-1273 was also more effective for improving antibody levels than ChAdOx1 (GMR = 11.09; 95% CI: 8.36-14.71) or NVX-CoV2373 (GMR = 2.87; 95% CI: 1.08-3.91). No significant difference in the risk for SAEs was found in any comparisons. CONCLUSIONS: Relative to vaccination with two doses of CoronaVac, a dose of BNT162b2 as a booster substantially enhances immunogenicity reactions and has a relatively acceptable risk for SAEs relative to other vaccines. For primary vaccination, schedules including mRNA vaccines induce a greater immune response. However, the comparatively higher risk for local and systemic adverse events introduced by mRNA vaccines should be noted. REGISTRATION PROSPERO; https://www.crd.york.ac.uk/PROSPERO/ ; No. CRD42021278149.
Adult ; Humans ; BNT162 Vaccine ; 2019-nCoV Vaccine mRNA-1273 ; Network Meta-Analysis ; Immunization Schedule ; COVID-19/prevention & control* ; COVID-19 Vaccines/adverse effects* ; Viral Vaccines ; mRNA Vaccines ; Antibodies, Neutralizing ; Antibodies, Viral

In order to increase the ability of oil-emulsion adjuvant to stimulate cellular immunity, chitosan hydrochloride with positive charge was selected to stabilize oil-in-water emulsion (CHE). In this paper, model antigen ovalbumin was selected to prepare vaccines with emulsion adjuvant, commercial adjuvant or no adjuvant. The emulsion was characterized by measuring the particle size, electric potential and antigen adsorption rate. BALB/c mice were immunized by intramuscular injection. Serum antibody levels, the numbers of IL-4-secreting cells in splenocytes, cytotoxic T lymphocyte (CTL) response, and the expression of central memory T cells were measured to evaluate the immunostimulatory effect. The results showed that chitosan hydrochloride can effectively stabilize the emulsion. The emulsion size is about 600 nm, and the antigen adsorption rate is more than 90%. After immunization, CHE could increase serum antibodies levels and increase IL-4 secretion. Expression of CTL surface activation molecules was also increased to stimulate CTL response further and to increase the CD44⁺CD62L⁺ in T cells proportion. CHE as adjuvant can stimulate humoral and cellular immunity more efficiently, and is expected to extend the duration of protection.
Animals ; Mice ; Chitosan ; Interleukin-4 ; Emulsions ; Immunization ; Adjuvants, Immunologic/pharmacology* ; Antigens ; Mice, Inbred BALB C

To prepare a lipid nanoparticle (LNP)-based subunit vaccine of Mycobacterium tuberculosis (Mtb) antigen EsxV and study its immunological characteristics, the LNP containing EsxV and c-di-AMP (EsxV: C: L) was prepared by thin film dispersion method, and its encapsulation rate, LNP morphology, particle size, surface charge and polyphase dispersion index were measured. BALB/c mice were immunized with EsxV: C: L by nasal drops. The levels of serum and mucosal antibodies, transcription and secretion of cytokines in lung and spleen, and the proportion of T cell subsets were detected after immunization. EsxV: C: L LNPs were obtained with uniform size and they were spherical and negatively charged. Compared with EsxV: C immunization, EsxV: C: L mucosal inoculation induced increased sIgA level in respiratory tract mucosa. Levels of IL-2 secreted from spleen and ratios of memory T cells and tissue-resident T cells in mice were also elevated. In conclusion, EsxV: C: L could induce stronger mucosal immunity and memory T cell immune responses, which may provide better protection against Mtb infection.
Animals ; Mice ; Mycobacterium tuberculosis ; Antigens, Bacterial ; Immunization ; Nanoparticles ; Vaccines, Subunit ; Mice, Inbred BALB C

To further enhance the immune effect of the foot-and-mouth disease (FMD) virus-like particles (VLPs) vaccine, this study prepared FMDV VLPs-zeolitic imidazolate (framework-8, ZIF-8) complexes with different particle sizes. We used a biomimetic mineralization method with Zn²⁺ and 2-methylimidazole in different concentration ratios to investigate the effect of size on the immunization effect. The results showed that FMDV VLPs-ZIF-8 with three different sizes were successfully prepared, with an approximate size of 70 nm, 100 nm, and 1 000 nm, respectively. Cytotoxicity and animal toxicity tests showed that all three complexes exhibited excellent biological safety. Immunization tests in mice showed that all three complexes enhanced the titers of neutralizing and specific antibodies, and their immune effects improved as the size of the complexes decreased. This study showed that ZIF-8 encapsulation of FMDV VLPs significantly enhanced their immunogenic effect in a size-dependent manner.
Animals ; Mice ; Foot-and-Mouth Disease/prevention & control* ; Foot-and-Mouth Disease Virus ; Antibodies, Neutralizing ; Immunity, Humoral ; Immunization ; Vaccines, Virus-Like Particle ; Antibodies, Viral ; Viral Vaccines

Objective To produce rabbit polyclonal antibody against mouse testis expressed 38 (TEX38). Methods Full-length open reading frame sequence of TEX38 was amplified and inserted into the pET-30a-(+) vector to construct pET-30a-TEX38 prokaryotic plasmid. The recombinant plasmid was transformed into E.coli BL21, and expression was induced with isopropyl β-D-thiogalactopyranoside (IPTG). New Zealand white rabbits were immunized with TEX38 protein after purification and denaturation, then TEX38 polyclonal antibodies were collected from rabbit serum samples. ELISA was performed to detect the antibody titer. Western blot and immunofluorescence staining were performed to determine the specificity of TEX38 polyclonal antibodies. Results The pET-30a-TEX38 recombinant plasmid was constructed, and TEX38 prokaryotic protein was expressed and purified successfully. After immunization, the titer of TEX38 antibody reached 1:1 000 000. Western blot analysis and immunofluorescence staining showed that TEX38 was localized in the mouse spermatogenic cells and sperms with a good specificity. Conclusion The rabbit polyclonal antibody against mouse TEX38 is successfully produced, and the expression of TEX38 in mouse spermatogenic cells and sperms is validated.
Male ; Rabbits ; Animals ; Mice ; Testis ; Antibodies ; Enzyme-Linked Immunosorbent Assay ; Immunization ; Spermatozoa ; Escherichia coli

INTRODUCTION: Cervical cancer has a high disease burden in Singapore, and it is strongly associated with human papillomavirus (HPV) infections. Despite constant efforts to encourage vaccination, local HPV vaccine uptake remains low. Universal mass vaccination is a proven cost-effective method to reduce the cervical cancer disease burden. This paper reviews the newly implemented school-based HPV vaccination programme in Singapore and the factors that led to its success. METHODS: Fully subsidised HPV vaccinations were offered to all Secondary 1 female students on an opt-in basis, starting as a rollout dose in 2019. One-time catchup vaccination was also offered to female students in Secondary 2-5. Eligible recipients were identified using enrolment data provided by Ministry of Education schools. A total of 19,144 students across 139 schools were offered the rollout dose, and 20,854 students across 140 schools were offered the catchup doses. RESULTS: High vaccine uptake rates of 80.6%-87.3% were noted with the introduction of the school-based programme, translating to high vaccine coverage of 90.3%-93.4%. Only a small proportion of students (1.5%-1.9% per cohort) opted out. The rate of reported side effects, which were commonly known effects, was low at one in 1000. Among the students who reported side effects, those who received the second vaccine dose did so uneventfully. CONCLUSION High HPV vaccine coverage was achieved after implementation of the school-based immunisation programme. Timely assessment of knowledge lapses and targeted intervention, strong partnerships with stakeholders, constant on-site adaptation and positive social influence contributed to its success. This model can be applied to future school health programmes.
Humans ; Female ; Papillomavirus Vaccines/therapeutic use* ; Human Papillomavirus Viruses ; Papillomavirus Infections/prevention & control* ; Singapore ; Uterine Cervical Neoplasms/epidemiology* ; Vaccination ; Immunization Programs

This study systematically retrieved information on the payment policy of vaccination fees for pneumococcal vaccines, human papillomavirus vaccines, haemophilus influenzae type b vaccines and rotavirus vaccines using a Python-based crawler. The proportion of the population covered by policies among the total applicable population was estimated based on the medical insurance coverage ratio and population data in 2020. This study showed that the payment policies included two categories, government-funded free vaccination policies and medical insurance payment policies. Among the four non-national immunization program vaccines, the free vaccination policies only involved pneumococcal vaccines and human papillomavirus vaccines. Among them, the 13-valent pneumococcal conjugate vaccine, the 23-valent pneumococcal polysaccharide vaccine, and the human papillomavirus vaccine were provided free of charge in 1, 10 and 15 provinces, respectively. For these policies, the corresponding covered population and the proportion among the total applicable population were children aged 6 months to 2 years old (2.5%), older people (1.2% to 21.5%) and middle school girls (1.1% to 12.2%). Medical insurance payment policies were implemented in 14 provinces, and nearly covered the four types of vaccines in the policy implementation areas, with the proportion of the covered population about 10.9% to 41.5% among the total applicable population.
Child ; Female ; Humans ; Infant ; Aged ; Pneumococcal Vaccines ; Vaccination ; Policy ; Immunization Programs ; Papillomavirus Vaccines ; China ; Vaccines, Conjugate