BACKGROUND: This study in 11- to 15-year-old boys and girls compared the immunogenicity and safety of GARDASIL 9 (9-valent human papillomavirus [9vHPV] vaccine) administered either concomitantly or nonconcomitantly with 2 vaccines routinely administered in this age group (Menactra [MCV4; Neisseria meningitidis serotypes A/C/Y/W-135] or Adacel [Tdap; diphtheria/tetanus/acellular pertussis]). METHODS: Participants received 9vHPV vaccine at day 1 and months 2 and 6; the concomitant group (n = 621) received MCV4/Tdap concomitantly with 9vHPV vaccine at day 1; the nonconcomitant group (n = 620) received MCV4/Tdap at month 1. Antibodies to HPV-, MCV4-, and Tdap-relevant antigens were determined. Injection-site and systemic adverse events (AEs) were monitored for 15 days after any vaccination; serious AEs were monitored throughout the study. RESULTS: The geometric mean titers for all HPV types in 9vHPV vaccine 4 weeks after dose 3, proportion of subjects with a fourfold rise or greater in titers for 4 N meningitidis serotypes 4 weeks after injection with MCV4, proportion of subjects with antibody titers to diphtheria and tetanus ≥0.1 IU/mL, and geometric mean titers for pertussis antigens 4 weeks after injection with Tdap were all noninferior in the concomitant group compared with the nonconcomitant group. Injection-site swelling occurred more frequently in the concomitant group. There were no vaccine-related serious AEs. CONCLUSIONS: Concomitant administration of 9vHPV vaccine with MCV4/Tdap was generally well tolerated and did not interfere with the antibody response to any of these vaccines. This strategy would minimize the number of visits required to deliver each vaccine individually.

Background: High‐income country studies show unfavorable trends in stroke incidence (SI) in younger populations. We aimed to estimate temporal change in SI disaggregated by age and sex in Latin America and the Caribbean region. Methods and Results: A search strategy was used in MEDLINE, WOS, and LILACS databases from 1997 to 2021, including prospective population‐based observational studies with first‐ever stroke incidence in Latin America. Reports without data broken down by age and sex were excluded. Risk of bias was assessed with The Joanna Briggs Institute's guide. The main outcomes were incidence rate ratio and relative temporal trend ratio of SI, comparing time periods before 2010 with after 2010. Pooled relative temporal trend ratios considering only studies with 2 periods in the same population were calculated by random‐effects meta‐analysis. Meta‐regression analysis was used to evaluate incidence rate determinants. From 9242 records identified, 6 studies were selected including 4483 first‐ever stroke in 4 101 084 individuals. Crude incidence rate ratio in younger subjects (<55 years) comparing before 2010:after 2010 periods showed an increase in SI in the past decade (incidence rate ratio, 1.37 [95% CI, 1.23–1.50]), in contrast to a decrease in older people during the same period (incidence rate ratio, 0.83 [95% CI, 0.76–0.89]). Overall relative temporal trend ratio (<55:≥55 years) was 1.65 (95 CI%, 1.50–1.80), with higher increase in young women (pooled relative temporal trend ratio, 3.08 [95% CI, 1.18–4.97]; P for heterogeneity <0.001). Conclusions: An unfavorable change in SI in young people, especially in women, was detected in population‐based studies in the past decade in Latin America and the Caribbean. Further investigation of the explanatory variables is required to ameliorate stroke prevention and inform local decision‐makers. Registration: URL: https://www.crd.york.ac.uk/prospero/ Identifier: CRD42022332563.

In 2006, the human papillomavirus (HPV) vaccine was approved for use as an effective intervention for reducing the risk of developing cervical cancer; however, its successful implementation is dependent on acceptability. This study aims to provide a comprehensive understanding of the reasons that favor or do not favor the acceptability of HPV vaccines. Methods: We conducted a systematic review and meta-summary of qualitative research on 16 databases. A total of 32 articles that considered the perspectives of vaccine users, their parents, and the professionals who care for them were reviewed. Synthesis was conducted as described by Sandelowski and Barroso. Results: We used inductive and deductive methods to obtain a total of 22 dimensions, out of which three issues stood out that should be considered to improve acceptability and are formed by three groups of study, namely, information about the vaccine, fears and side effects, and sexuality associated with the vaccine. Conclusions: Acceptability, as well as adherence to HPV vaccination, is a complex concept. This review highlights the perspectives of the three sets of actors involved in the process (i.e., users, parents, and professionals) and views these factors in relation to acceptability as a guide for new interventions.

Annual vaccination is an effective strategy for preventing severe disease caused by seasonal influenza. Quadrivalent influenza vaccines (QIVs) protect against two strains of influenza A and two strains of influenza B, thereby enhancing the host antiviral neutralizing antibody response and inducing CD4⁺ and CD8⁺ T cell responses. Here, we report findings from a randomized, double-blind, active-controlled phase 3 clinical trial (NCT05431725) that includes 334 healthy adults aged 18–64 years and evaluates the humoral and cellular antiviral immune responses induced by two inactivated QIVs, Sinovac-QIV and Vaxigrip-Tetra™. The primary endpoint of the study is the specific antibody responses measured by hemagglutination inhibition (HAI) assays 28 days post-vaccination, while the secondary endpoint is virus-specific T cell responses. Both QIVs elicit significant increases in antibody titers 28 days after vaccination; Sinovac-QIV induces 9–10-fold increases in geometric mean titers, while Vaxigrip-Tetra™ elicits 7–8-fold increases (p < 0.05). Cellular immune responses using ELISPOT and supervised and unsupervised flow cytometry analyses show that both vaccines modulate the frequency of hemagglutinin-specific CD4⁺ and CD8⁺ T cell subsets, inducing distinct T cell response profiles. Although cellular analyses are evaluated in a subgroup of the cohort, the data indicate that both QIVs induce robust humoral and cellular immunity in adults, providing mechanistic insights into vaccine-induced protection.

Several vaccines have been developed to control the COVID-19 pandemic. CoronaVac^®, an inactivated SARS-CoV-2 vaccine, has demonstrated safety and immunogenicity, preventing severe COVID-19 cases. We investigate the safety and non-inferiority of two immunization schedules of CoronaVac^® in a non-inferiority trial in healthy adults. A total of 2302 healthy adults were enrolled at 8 centers in Chile and randomly assigned to two vaccination schedules, receiving two doses with either 14 or 28 days between each. The primary safety and efficacy endpoints were solicited adverse events (AEs) within 7 days of each dose, and comparing the number of cases of SARS-CoV-2 infection 14 days after the second dose between the schedules, respectively. The most frequent local AE was pain at the injection site, which was less frequent in participants aged ≥60 years. Other local AEs were reported in less than 5% of participants. The most frequent systemic AEs were headache, fatigue, and myalgia. Most AEs were mild and transient. There were no significant differences for local and systemic AEs between schedules. A total of 58 COVID-19 cases were confirmed, and all but 2 of them were mild. No differences were observed in the proportion of COVID-19 cases between schedules. CoronaVac^® is safe, especially in ≥60-year-old participants. Both schedules protected against COVID-19 hospitalization.