Influenza Vaccine Dose-Sparing Possible Without Compromising Safety

influenza dosage
influenza dosage
A prospective multicenter study examined the optimal dose of seasonal trivalent influenza vaccines.

Influenza vaccine dose-sparing in adults and elderly patients was found to be safe with the use of whole-viron vaccines and aluminum adjuvants, according to a study published in the British Journal of Clinical Pharmacology.

Zoltan Vajo, MD, PhD, of the department of family practice at Semmelweis University in Budapest, Hungary, and colleagues completed a prospective, multicenter, randomized, double-blind clinical trial to establish an optimal dose for seasonal trivalent influenza vaccines

Currently licensed seasonal trivalent influenza vaccines include 15 μg haemagglutinin (HA) per virus strain for adult patients, and up to 60 μg for elderly patients. During the study, which ran from September 5 to October 17, 2011 in Budapest, researchers tested the immunogenicity of 4 different 0.5 ml dosages — 3.5 μg, 6 μg, 9 μg, and 15 μg HA — of the following vaccine strains:

The researchers also assessed the dose-effect relationship and immune response of the 4 vaccines 21 days post-vaccination, measured by haemagglutination inhibition (HI) test. 

The study hosted 256 participants: 127 adult participants age 18 to 60 years and 129 elderly participants, age >60 years (all white), randomly assigned to groups of 4 for each influenza vaccination dose; each group was split between the 2 age groups. A total of 254 participants were used for final evaluation. 

The immunogenicity outcomes were assessed according to European Medicines Agency Committee for Medicinal Products for Human Use (CHMP) criteria, which include post-vaccination titres and post- and pre-vaccination GMT ratios after 21 days of vaccination. 

The results found that all 4 vaccines with 3.5, 6, 9, and 15 μg HA per strain fulfilled CHMP criteria 21 days after vaccination with the 6 μg and 9 μg HA dose, showing no significant differences compared with the 15 μg HA dose in adults or elderly participants.   

Compared with the 3.5 μg HA dose, the 15 μg HA dose showed a significant difference between the percentage of adult participants showing seroconversion of a significant increase in antibody titres 21 days after vaccination for vaccine strain H3N2 only, −0.28 (95% CI, −0.51 to −0.03). 

“This was a somewhat unexpected finding, and it can possibly be explained by higher exposure rates to H3N2 during the 1968 pandemic in the elderly subject group,” the researchers noted. “[T]here is no clear dose-response relationship for immunogenicity between 6 μg and 15 μg HA per strain for the seasonal trivalent influenza vaccine studied in the present trial in adult and elderly patients.” 

Study Limitations

  • The study had low statistical power for detecting differences in immunogenicity or adverse events
  • Effects of dose reductions were not tested in pediatric patients or patients younger than 18
  • Results may not be generalizable to other groups as all study participants were white

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Vajo Z, Balaton G, Vajo P, Kalabay L, Erdman A, Torzsa P. Dose sparing and the lack of a dose-response relationship with an influenza vaccine in adult and elderly patients- a randomized, double blind clinical trial [Published online April 5, 2017]. Br J Clin Pharmacol. doi:10.1111/bcp.13289