Improved immunologic responses to heterologous influenza strains in children with low preexisting antibody response vaccinated with MF59-adjuvanted influenza vaccine

Biodistribution and mechanisms of action of MF59 and MF59-like adjuvants

Recently, adjuvants have received increasing attention as essential vaccine components. Nearly 100 years have passed since Gaston Roman introduced the concept of adjuvants in 1925, during which numerous preclinical and clinical studies related to vaccine adjuvants have been conducted. However, to date, only a few adjuvants have been successfully used in marketed vaccines. This low clinical translational efficiency is mainly owing to the lack of comprehensive and in-depth understanding of the mechanisms of action of adjuvants in complex biological systems. In fact, MF59 is the first non‑aluminum adjuvant applied in approved human vaccines and is still used today; however, many unknowns regarding its mechanism of action remain. Therefore, in this review, the current status of the mechanism of action of MF59 and MF59-like adjuvants is discussed based on evidence-based temporal and spatial processes of immune-regulatory events. Moreover, the key factors of MF59 and MF59-like adjuvants that regulate humoral and cellular immune responses have been summarized. In addition, studies on the distribution and elimination of both antigens and adjuvants were analyzed based on published studies to gain mechanistic insights into the safety of MF59-adjuvanted vaccines. This review will not only benefit future prospects for the development of novel squalene-based adjuvants and their use in clinical applications but will also be valuable for future mechanistic investigations on other vaccine adjuvants.

Committee on Infectious Diseases, O’Leary ST, Campbell JD, Ardura MI, Bryant KA, Caserta MT, Espinosa C, Frenck RW, Healy CM, John CC, Kourtis AP, Milstone A, Myers A, Pannaraj P, Ratner AJ, Bryant KA, Hofstetter AM, Chaparro JD, Michel JJ, Kimberlin DW, Banerjee R, Barnett ED, Lynfield R, Sawyer MH, Barton-Forbes M, Cardemil CV, Farizo KM, Kafer LM, Moore D, Okeke C, Prestel C, Patel M, Starke JR, Thompson J, Torres JP, Wharton M, Woods CR, Gibbs G. Recommendations for Prevention and Control of Influenza in Children, 2024-2025: Technical Report

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2024 to 2025 season. The rationale for the American Academy of Pediatrics recommendation for annual influenza vaccination of all children without medical contraindications starting at 6 months of age is provided. Influenza vaccination is an important strategy for protecting children and the broader community against influenza. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage and provides detailed guidance on vaccine storage, administration, and implementation. The report also provides a brief background on inactivated (nonlive) and live attenuated influenza vaccines, available vaccines for the 2024-2025 influenza season, vaccination during pregnancy and breastfeeding, diagnostic testing for influenza, and antiviral medications for treatment and chemoprophylaxis. Strategies to promote vaccine uptake are emphasized.

COMMITTEE ON INFECTIOUS DISEASES, O’Leary ST, Campbell JD, Ardura MI, Banerjee R, Bryant KA, Caserta MT, Frenck RW, Gerber JS, John CC, Kourtis AP, Myers A, Pannaraj P, Ratner AJ, Shah SS, Bryant KA, Hofstetter AM, Chaparro JD, Michel JJ, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH, Bernstein HH, Cardemil CV, Farizo KM, Kafer LM, Kim D, López Medina E, Moore D, Panagiotakopoulos L, Romero JR, Sauvé L, Starke JR, Thompson J, Wharton M, Woods CR, Frantz JM, Gibbs G. Recommendations for Prevention and Control of Influenza in Children, 2023-2024

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2023-2024 season. The rationale for the American Academy of Pediatrics recommendation for annual influenza vaccination of all children without medical contraindications starting at 6 months of age is provided. Influenza vaccination is an important strategy for protecting children and the broader community against influenza. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage, and provides detailed guidance on vaccine storage, administration, and implementation. The report also provides a brief background on inactivated and live-attenuated influenza vaccines, available vaccines this season, vaccination during pregnancy and breastfeeding, diagnostic testing for influenza, and antiviral medications for treatment and chemoprophylaxis. Strategies to promote vaccine uptake are emphasized.

Recommendations for Prevention and Control of Influenza in Children, 2022-2023

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2022 to 2023 season. The American Academy of Pediatrics recommends annual influenza vaccination of all children without medical contraindications starting at 6 months of age. Influenza vaccination is an important strategy for protecting children and the broader community as well as reducing the overall burden of respiratory illnesses when other viruses, including severe acute respiratory syndrome-coronavirus 2, are cocirculating. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage, and provides detailed guidance on storage, administration, and implementation. The report also provides a brief background on inactivated and live attenuated influenza vaccine recommendations, vaccination during pregnancy and breastfeeding, diagnostic testing, and antiviral medications for treatment and chemoprophylaxis. Updated information is provided about the 2021 to 2022 influenza season, influenza immunization rates, the effectiveness of influenza vaccination on hospitalization and mortality, available vaccines, guidance for patients with history of severe allergic reactions to prior influenza vaccinations, and strategies to promote vaccine uptake.

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.