Comparison of pneumococcal conjugate vaccine (PCV-13) cellular immune responses after primary and booster doses of vaccine

A comprehensive method for the phenotypical and functional characterization of recalled human memory B and T cells specific to vaccine antigens

Current methodologies for assessing vaccine effectiveness and longevity primarily center on measuring vaccine-induced neutralizing antibodies in serum or plasma. However, these methods overlook additional parameters such as the presence of memory B cells, even as antibody levels wane, and the pivotal role played by memory T cells in shaping antigen-specific memory B cell responses. Several studies have employed a combination of polyclonal activators, such as CpG and R848, along with various cytokines to provoke the recall of memory B cells from peripheral blood mononuclear cells (PBMCs) into antibody-secreting cells (ASCs). Other studies have examined the use of live attenuated viruses to stimulate antigen-specific memory T cells within PBMCs into effector T cells that produce Th1/Th2 cytokines. However, these studies have not fully elucidated the distinct effects of these polyclonal activators on individual subsets, nor have they evaluated whether the vaccine antigen alone is sufficient to trigger the recall of memory T cells. Thus, in this study, we directly compared the capacity of two B cell polyclonal activators to induce the transition of existing vaccine-specific memory cells present in peripheral blood samples into ASCs. Simultaneously, we also assessed the transition of existing memory T cells into effector subsets in response to vaccine antigens. Our findings demonstrate that both polyclonal activator combinations, CpG with IL-6 and IL-15, as well as R848 with IL-2, effectively induce the terminal differentiation of memory B cells into ASCs. Notably, CpG treatment preferentially expanded naïve and non-class-switched B cells, while R848 expanded class-switched memory cells, plasmablasts, and plasma cells. Consequently, R848 treatment led to a greater overall production of total and antigen-specific IgG immunoglobulins. Additionally, the exposure of isolated PBMCs to vaccine antigens alone proved sufficient for recalling the rare antigen-specific memory T cells into effector subsets, predominantly consisting of IFN-γ-producing CD4 T cells and TNF-β-producing CD8 T cells. This study not only establishes a rationale for the selection of methods to expand and detect antigen-specific lymphocyte subsets but also presents a means to quantify vaccine effectiveness by correlating serum antibody levels with preexisting memory cells within peripheral blood samples.

Evolution of Pneumococcal Vaccine Recommendations and Criteria for Decision Making in 5 Western European Countries and the United States

Objectives

Pneumococcal vaccine recommendations have become increasingly complex. This study aims to understand how national immunization technical advisory groups (NITAGs) and health technology assessment (HTA) agencies of 5 European countries and the United States formed their pneumococcal vaccine recommendations, by providing reviewed evidence and key drivers for new recommendations.

Methods

Centers for Disease Control and Prevention, European Centre for Disease Prevention and Control, and National Health Authorities Web sites were screened to capture the evolution of pneumococcal recommendations. A narrative review was conducted on NITAGs and HTA bodies' Web sites. Assessments of pneumococcal vaccines published from 2009 to 2022 were included.

Results

Thirty-four records were identified including 21 assessments for risk groups, 17 for elderly, and 12 for children. Burden of disease and vaccine characteristics were almost systematically reviewed during assessments. All 6 countries recommended the use of higher-valent pneumococcal vaccine (PCV; i.e., PCV10 and PCV13) in childhood vaccination programs, given their broader serotype coverage and their comparable profile to PCV7. PCV13 was progressively added to the vaccine schedule (in addition to polysaccharide vaccine) in at least the high-risk group, given the high burden in this population and expected additional benefits of PCV13. For the elderly, unlike the United States, European countries issued negative recommendation for PCV13 routine use because of substantial herd effects from childhood vaccination program making PCV13 likely not cost-effective.

Conclusions

This research provides an overview of decision-making processes for higher-valent PCVs recommendations and could be of interest to anticipate the place of next generation of PCVs in the vaccination landscape.

Highlights

By describing evidence-based criteria for decision making, this study emphasizes the framework analysis of NITAGs and HTA bodies when assessing pneumococcal vaccines and demonstrates that variation exists between countries and also according to population evaluated.While the burden of disease and immunogenicity/efficacy data were almost systematically reviewed by national stakeholders, economic assessments were reported to a lesser extent but played a major role in the limited use of PCV13 in the adult population.

Pneumococcal Conjugated Vaccines Decreased Acute Otitis Media Burden: A Population-Based Study in Israel

OBJECTIVE

To study time trends in all-cause acute otitis media (AOM) burden by calculating incidence rates of AOM episodes and recurrent acute otitis media (rAOM) cases in highly immunized pediatric population during the pre- and post-pneumococcal conjugated vaccine (PCV) years.

STUDY DESIGN

In this population-based study, AOM episodes and rAOM cases were identified in Clalit Health Services-insured Israeli children aged 0-10 years between 2005 and 2018 by using a data-sharing platform. Because a near-sequential implementation of PCV-7/PCV-13 occurred within a 1-year period (2009/2010), we compared AOM visits before (2005-July 2009) and after (August 2009-2018) the introduction of PCVs. We focused on children younger than 2 years of age, who are the target population of PCVs and are at AOM peak age.

RESULTS

We identified 805 389 AOM episodes contributed by 270 137 children. The median number of AOM episodes was 2 (IQR 1-4). A downward trend of incidence rates of AOM episodes was observed during the post-PCV years in children younger than age 9 years (P < .001). The largest decrease (21%) was observed in children younger than 1 year, from 807/1000 children during the pre-PCV years to 640/1000 during the post-PCV years (P < .001). An average annual decrease of ∼14/1000 AOM episodes was calculated in children younger than 1 year old (β = -13.39, 95% CI -16.25 to -10.53, P < .001). Of rAOM cases, documented in 84 237 (31.2%) children, 74% were in children younger than 2 years, and 55% were in boys. The risk to develop rAOM significantly decreased during the post-PCV years in children younger than 2 years (hazard ratio 0.893, 95% CI 0.878-0.908; P < .001).

CONCLUSIONS

AOM burden significantly decreased following PCVs introduction in highly immunized children.