Immunization of preterm infants: current evidence and future strategies to individualized approaches

Diet, microbiome, and probiotics establish a crucial link in vaccine efficacy

Vaccination plays a critical role in public health by reducing the incidence and prevalence of infectious diseases. The efficacy of a vaccine has numerous determinants, which include age, sex, genetics, environment, geographic location, nutritional status, maternal antibodies, and prior exposure to pathogens. However, little is known about the role of gut microbiome in vaccine efficacy and how it can be targeted through dietary interventions to improve immunological responses. Unveiling this link is imperative, particularly in the post-pandemic world, considering impaired COVID-19 vaccine response observed in dysbiotic individuals. Therefore, this article aims to comprehensively review how diet and probiotics can modulate gut microbiome composition, which is linked to vaccine efficacy. Dietary fiber and polyphenolic compounds derived from plant-based foods improve gut microbial diversity and vaccine efficacy by promoting the growth of short-chain fatty acids-producing microbes. On the other hand, animal-based foods have mixed effects - whey protein and fish oil promote gut eubiosis and vaccine efficacy. In contrast, lard and red meat have adverse effects. Studies further indicate that probiotic supplements exert varied effects, mostly strain and dosage-specific. Interlinking diet, microbiome, probiotics, and vaccines will reveal opportunities for newer research on diet-induced microbiome-manipulated precision vaccination strategies against infectious diseases.

Rotavirus Vaccine Administration in Preterm and Medically Fragile Infants Admitted to Neonatal Intensive Care Units: Second Phase Enrollments and Final Results of a Multicenter Observational Study Conducted in Sicily, Italy

Rotavirus disease is the world's leading cause of severe gastroenteritis and mortality in children up to 5 years of age. Premature infants are more vulnerable to rotavirus gastroenteritis (RVGE) and its complications. International authorities strongly recommend vaccination because of the consistent reduction in infections, hospitalizations, deaths, and related costs.

BACKGROUND/OBJECTIVES

The objective of the present study was to evaluate the safety of anti-rotavirus vaccination in premature infants admitted and vaccinated in the main Sicilian Neonatal Intensive Care Units (NICUs) during the pandemic period.

METHODS

The human monovalent rotavirus vaccination (RV1) was administered to preterm infants of gestational age ≥28 weeks in the main Sicilian NICUs from January 2020 to December 2022, as a prolongation of a similar study conducted from April 2018 to December 2019. Rotavirus vaccinations were provided both to hospitalized infants and to those returning for post-discharge follow-up, beginning at six weeks of age according to the official immunization schedule. All potential adverse events-whether expected, unexpected, or serious-were recorded from the day of vaccination through 14 days (first follow-up) and 28 days (second follow-up) after each of the two scheduled doses.

RESULTS

A total of 355 preterm infants were fully vaccinated with RV in four Sicilian NICUs. The mean gestational age of newborns was 33.2 weeks (±2.7), 53% of whom were male. Vaccination was performed on average at 7 weeks of age (±2.1), and the mean weight at the time of vaccination was 3439 g (SD ± 745.2). No expected/unexpected or serious adverse events were observed either within the 14-day or within the 28-day period after administration of both two doses.

CONCLUSIONS

Data confirm that vaccination in preterm infants ≥28 weeks gestational age is safe. The prolongation of this Public Health strategy, strongly recommended by the Sicilian Health Department during the pandemic period that also generally has led to a reduction of vaccination adherence and acceptance of pediatric vaccination, demonstrates the importance of multidisciplinary collaboration with neonatologists and pediatricians to continue promoting in-hospital vaccinations for fragile subjects.

Influenza Immunization in Very-Low-Birth-Weight Infants: Epidemiology and Long-Term Outcomes

BACKGROUND

Very-low-birth-weight infants (VLBWIs; birth weight < 1500 g) are at an increased risk of complicated influenza infection, which frequently includes pneumonia, encephalitis or even death. Data on influenza immunization and its outcome in VLBWIs are scarce. This study aimed to provide epidemiological data on influenza immunization for German VLBWIs and hypothesized that immunization would protect VLBWIs from infection-mediated neurodevelopmental impairment and preserves lung function at early school age.

METHODS

In this observational population-based German Neonatal Network (GNN) study, infants born between 2009 and 2015 were invited to partake in a 6-year follow-up investigation including lung function and developmental testing. Uni- and multivariate analyses were performed to evaluate the clinical characteristics and outcomes of influenza-immunized VLBWIs compared to non-immunized VLBWIs.

RESULTS

Influenza immunization was performed in 871 out of the 3358 VLBWIs (26%) with six-year follow-up. Immunized infants were characterized by a low gestational age and higher rates of morbidity, particularly bronchopulmonary dysplasia. Although early immunization showed no safety signals and had protective effects on the long-term risk of bronchitis (OR: 0.2; CI: 0.1-0.6; p = 0.002), most VLBWIs (88.0%) were unimmunized in their first influenza season.

CONCLUSIONS

Influenza immunization was not associated with improved lung function (forced expiratory volume in one second and forced vital capacity) or a better neurocognitive outcome (intelligence quotient and strengths and difficulties questionnaire) at early school age. In Germany, only one quarter of 6-year-old VLBWIs were immunized against influenza, particularly those born <28 gestational weeks and/or BPD. Specific influenza immunization guidelines that define evidence-based recommendations are needed for this vulnerable group.

Precision Nanovaccines for Potent Vaccination

Compared with traditional vaccines, nanoparticulate vaccines are especially suitable for delivering antigens of proteins, peptides, and nucleic acids and facilitating lymph node targeting. Moreover, apart from improving pharmacokinetics and safety, nanoparticulate vaccines assist antigens and molecular adjuvants in crossing biological barriers, targeting immune organs and antigen-presenting cells (APC), controlled release, and cross-presentation. However, the process that stimulates and orchestrates the immune response is complicated, involving spatiotemporal interactions of multiple cell types, including APCs, B cells, T cells, and macrophages. The performance of nanoparticulate vaccines also depends on the microenvironments of the target organs or tissues in different populations. Therefore, it is necessary to develop precise nanoparticulate vaccines that accurately regulate vaccine immune response beyond simply improving pharmacokinetics. This Perspective summarizes and highlights the role of nanoparticulate vaccines with precise size, shape, surface charge, and spatial management of antigen or adjuvant for a precision vaccination in regulating the distribution, targeting, and immune response. It also discusses the importance of the rational design of nanoparticulate vaccines based on the anatomical and immunological microstructure of the target tissues. Moreover, the target delivery and controlled release of nanovaccines should be taken into consideration in designing vaccines for achieving precise immune responses. Additionally, it shows that the nanovaccines remodel the suppressed tumor environment and modulate various immune cell responses which are also essential.

Persistence of antibodies 5 years after hepatitis B vaccination in preterm birth children: A retrospective cohort study using real-world data

Previous studies did not provide substantial evidence for long-term immune persistence after the hepatitis B vaccine (HepB) in preterm birth (PTB) children. Consequently, there is ongoing controversy surrounding the booster immunization strategy for these children. Therefore, we conducted a retrospective cohort study to evaluate the disparities in immune persistence between PTB children and full-term children. A total of 1027 participants were enrolled in this study, including 505 PTB children in the exposure group and 522 full-term children in the control group. The negative rate of hepatitis B surface antibody (HBsAb) in the PTB group was significantly lower than that in the control group (47.9% vs. 41.4%, p = .035). The risk of HBsAb-negative in the exposure group was 1.5 times higher than that in the control group (adjusted odds ratio [aOR] = 1.5, 95% confidence interval [CI]: 1.1-2.0). The geometric mean concentration (GMC) of HBsAb was much lower for participants in the exposure group compared to participants in the control group (9.3 vs. 12.4 mIU/mL, p = .029). Subgroup analysis showed that the very preterm infants (gestational age <32 weeks) and the preterm low birth weight infants (birth weight <2000 g) had relatively low GMC levels of 3.2 mIU/mL (95% CI: 0.9-11.1) and 7.9 mIU/mL (95% CI: 4.2-14.8), respectively. Our findings demonstrated that PTB had a significant impact on the long-term persistence of HBsAb after HepB vaccination. The very preterm infants (gestational age <32 weeks) and the preterm low birth weight infants (birth weight <2000 g) may be special populations that should be given priority for HepB booster vaccination.

Strategies for Working With Parents With Vaccination Hesitancy

The purpose of this article is to provide an overview of effective strategies for working with parents' vaccination hesitancy or refusal. An overview of historical and current trends in vaccination hesitancy and factors that contribute to and strategies for addressing vaccine hesitancy are discussed. This includes an emphasis on the critical role played by health care providers, as trusted advisors and a primary source of health care information, in encouraging vaccine acceptance. Legal and ethical implications are also considered. Vaccination hesitancy strategies are most effective if they are timely, multifaceted, and collaborative.

Age-related changes of the human splenic marginal zone B cell compartment

In this review, we will summarize the growing body of knowledge on the age-related changes of human splenic B cell composition and molecular evidence of immune maturation and discuss the contribution of these changes on splenic protective function. From birth on, the splenic marginal zone (sMZ) contains a specialized B cell subpopulation, which recruits and archives memory B cells from immune responses throughout the organism. The quality of sMZ B cell responses is augmented by germinal center (GC)-dependent maturation of memory B cells during childhood, however, in old age, these mechanisms likely contribute to waning of splenic protective function.

An update on vaccination in preterm infants

OBJECTIVE

The objective of this article is to review the most current literature on vaccines, focusing on their safety, immunogenicity, and efficacy in preterm newborns, aiming to improve vaccine coverage in this population.

DATA SOURCE

Most recent scientific publications addressing the immunization of preterm newborns.

DATA SYNTHESIS

Despite its immunological immaturity, vaccination is well tolerated by preterm infants, and protective immune responses are observed, but some studies have shown that preterm infants undergo unjustified delays in their vaccination schedule.

CONCLUSIONS

Despite being widely recommended, the routine immunization of preterm infants is often delayed, putting this vulnerable population at risk for several diseases, many of which are preventable by immunization. Every effort should be made to develop universal guidelines that define the immunization of preterm infants.

A retrospective study of hepatitis B vaccination in preterm birth and low birth weight infants born to hepatitis B surface antigen-positive mothers: Time to close the policy-practice gap

National Immunization Program-version 2016 (ISIV-NIP-v2016) recommended a 4-dose hepatitis B vaccine (HepB) schedule for preterm birth (PTB) and low birth weight (LBW) infants born to HBsAg-positive mothers. However, the implementation of this immunization strategy in the past five years has not been fully evaluated in China. We reviewed the data of pregnant women and live-born infants from 24 hospitals between 2016 and 2021 in Lu'an, Anhui province, to estimate the prevalence of PTB, LBW, and hepatitis B virus (HBV) infected pregnant women. We analyzed the vaccination status of HepB and HBIG among PTB and LBW infants born to HBsAg-positive mothers. A total of 160 222 pregnant women and 159 613 live-born infants were included in this study. The estimated prevalence of PTB, LBW and HBV-infected pregnant women was 3.86% (range: 3.28%-5.10%), 2.77% (range: 2.12%-3.66%), and 3.27% (range: 3.03%-3.49%), respectively. We screened 340 PTB and LBW infants born to HBsAg-positive mothers between 2016 and 2020. We found that the coverage of HepB and HBIG among them was 100% and 99.39%. However, the timely vaccination rate of the HepB birth dose was only 78.59% and only four children (1.22%) received the 4-dose HepB as recommended by ISIV-NIP-v2016. The 4-dose of HepB for PTB and LBW infants born to HBsAg-positive mothers recommended by ISIV-NIP-v2016 was not fully implemented. A strong public health intervention should be taken to close the policy-practice gap in China in the future.