During the 2022-2023 flu season, high-dose and adjuvanted influenza vaccines demonstrated superior efficacy in reducing flu symptoms and hospital admissions among individuals aged 65 and over compared to the standard flu vaccine, according to a study. The research, titled “Comparative effectiveness of licensed influenza vaccines in preventing influenza-related medical encounters and hospitalisations in the 2022-2023 influenza season among adults ≥65 years of age,” was published on August 21, 2024, in the journal Clinical Infectious Diseases.
Jennifer Ku, PhD, MPH, an infectious disease epidemiologist at the Kaiser Permanente Southern California Department of Research & Evaluation, emphasised the benefits of opting for either high-dose or adjuvanted flu vaccines over the standard option for the elderly. She noted that despite seasonal variations, the enhanced vaccines consistently provide better protection for seniors against conventional flu shots, which are typically weaker.
Vaccination remains the most effective measure to prevent influenza and mitigate the severity of its symptoms. Traditional flu vaccines are produced by growing the viruses in chicken eggs; however, newer formulations such as high-dose, adjuvanted, and recombinant vaccines have been developed to enhance the efficacy and production of flu vaccines. The high-dose vaccine contains a quadruple amount of antigen compared to the standard vaccines. Adjuvanted vaccines include an additional component that boosts the immune response. Recombinant vaccines, which use gene technology and do not depend on eggs for production, were less commonly used within Kaiser Permanente in Southern California and, hence, were not part of this study.
In 2022, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) advised the use of high-dose, adjuvanted, or recombinant vaccines over the standard dose vaccines for adults aged 65 years and older, who are more susceptible to severe illness, hospitalisation, and death from influenza.
The study analysed data from nearly half a million seniors who received at least one dose of a flu vaccine during the season. It found that the high-dose and adjuvanted vaccines were significantly more effective at preventing hospitalisations due to flu, with 25% and 62% effectiveness estimates, respectively, compared to the standard dose vaccine. Furthermore, the effectiveness of high-dose and adjuvanted vaccines for healthcare visits due to flu were 9% and 17%, respectively.
Hung Fu Tseng, PhD, MPH, a senior scientist at the Department of Research & Evaluation and senior author of the study, highlighted that this was the first real-world evaluation comparing high-dose and adjuvanted flu vaccines against the more traditional standard-dose egg-based vaccines following ACIP’s preferential recommendation. The findings strongly support ACIP’s guidance to vaccinate seniors with the more potent high-dose and adjuvanted flu vaccines, underscoring their excellent protective benefits in this vulnerable age group.
More information: Jennifer Ku et al, Comparative Effectiveness of Licensed Influenza Vaccines in Preventing Influenza-related Medical Encounters and Hospitalizations in the 2022–2023 Influenza Season Among Adults ≥65 Years of Age, Clinical Infectious Diseases. DOI: 10.1093/cid/ciae375
Journal information: Clinical Infectious Diseases Provided by Kaiser Permanente
