Safety and immunogenicity of high doses of quadrivalent influenza vaccine in children 6 months through <18 years of age: A randomized controlled phase II dose-finding trial

Unlocking the Power of Influenza Vaccines for Pediatric Population: A Narrative Review

The flu, often known as influenza, is a dangerous public health hazard for the pediatric population. Immunization is essential for decreasing the burden of the disease and avoiding complications related to influenza. However, the immunogenicity, efficacy, and safety of different influenza vaccines in children warrant careful evaluation. The purpose of this narrative review is to give a summary of the existing literature on the immunogenicity, efficacy, and safety of several vaccinations against influenza viruses in children. The review incorporates evidence from a range of studies focusing on the outcomes of interest. Immunogenicity studies have shown that influenza vaccines induce a robust immune response in children, primarily through neutralizing antibodies' formation. However, variations in vaccine composition influence the duration and magnitude of immune responses. Safety is a crucial consideration in pediatric vaccination. In children, influenza vaccinations have generally shown a high safety profile, with mild and temporary side effects being the most common. Vaccinations against influenza have shown a modest level of efficacy in avoiding hospitalizations linked to influenza, laboratory-confirmed influenza infections, and serious consequences in children. Live attenuated vaccines have shown higher effectiveness against matched strains compared to inactivated vaccines. In conclusion, this narrative review highlights that receiving influenza vaccination in children aged six to 47 months is very important. While different vaccines exhibit varying immunogenicity, safety profiles, and effectiveness, they all contribute to reducing the burden of influenza among children. Future research should focus on optimizing vaccine strategies, improving vaccine coverage, and evaluating long-term protection.

Epidemiology, Clinical Characteristics, and Outcomes of Influenza-Associated Hospitalizations in US Children Over 9 Seasons Following the 2009 H1N1 Pandemic

BACKGROUND

Recent population-based data are limited regarding influenza-associated hospitalizations in US children.

METHODS

We identified children <18 years hospitalized with laboratory-confirmed influenza during 2010-2019 seasons, through the Centers for Disease Control and Prevention's Influenza Hospitalization Surveillance Network. Adjusted hospitalization and in-hospital mortality rates were calculated, and multivariable logistic regression was conducted to evaluate risk factors for pneumonia, intensive care unit (ICU) admission, mechanical ventilation, and death.

RESULTS

Over 9 seasons, adjusted influenza-associated hospitalization incidence rates ranged from 10 to 375 per 100 000 persons each season and were highest among infants <6 months old. Rates decreased with increasing age. The highest in-hospital mortality rates were observed in children <6 months old (0.73 per 100 000 persons). Over time, antiviral treatment significantly increased, from 56% to 85% (P < .001), and influenza vaccination rates increased from 33% to 44% (P = .003). Among the 13 235 hospitalized children, 2676 (20%) were admitted to the ICU, 2262 (17%) had pneumonia, 690 (5%) required mechanical ventilation, and 72 (0.5%) died during hospitalization. Compared with those <6 months of age, hospitalized children ≥13 years old had higher odds of pneumonia (adjusted odds ratio, 2.7 [95% confidence interval, 2.1-3.4], ICU admission (1.6 [1.3-1.9]), mechanical ventilation (1.6 [1.1-2.2]), and death (3.3 [1.2-9.3]).

CONCLUSIONS

Hospitalization and death rates were greatest in younger children at the population level. Among hospitalized children, however, older children had a higher risk of severe outcomes. Continued efforts to prevent and attenuate influenza in children are needed.

Influenza vaccines: where we are, where we are going

PURPOSE OF REVIEW

Influenza vaccines are the most useful strategy for preventing influenza illness, especially in the setting of the COVID-19 pandemic. For the coming year (2021/2022) all vaccines will be quadrivalent and contain two influenza A strains [(H1N1)pdm09-like and (H3N2)-like viruses] and two influenza B strains (Victoria lineage-like and Yamagata lineage-like viruses). However, the currently licensed have suboptimal efficacy due to the emergence of new strains and vaccine production limitations. In this review, we summarize the current recommendations as well as new advancements in influenza vaccinations.

RECENT FINDINGS

Recent advances have been aimed at moving away from egg-based vaccines and toward cell culture and recombinant vaccines. This removes egg adaptations that decrease vaccine efficacy, removes the reliance on egg availability and decreases the time necessary to manufacture vaccines. However, even more radical changes are needed if we are to reach the ultimate goal of a universal vaccine capable of providing long-lasting protection against all or at least most influenza strains. We discuss various strategies, including using more stable influenza antigens such as the hemagglutinin stalk and internal proteins as well as new adjuvants, new vaccine formulations, and DNA/RNA-based vaccines that are currently being developed.

SUMMARY

The currently available vaccines have suboptimal efficacy and do not provide adequate protection against drifted and shifted strains. Thus, the development of a universal influenza vaccine that induces long-lasing immunity and protects against a broad range of strains is crucial.