A simple and cost-neutral manipulation of the timing of flu vaccine administration – vaccinating older adults in the morning – may improve protection from the influenza virus, according to a study published in Vaccine.

Anna C. Phillips, PhD, of the School of Sport, Exercise, and Rehabilitation Sciences at the University of Birmingham (England), and her associates assessed the change in antibody titers to three vaccine influenza strains (A/H1N1, A/H3N2, and B) from prevaccination to one month postvaccination in a non-blinded cluster-randomized trial of 276 adults aged 65 or older receiving vaccinations in the morning or afternoon between October 28, 2011 and November 12, 2013. Because diurnal variations in immune cell responses and/or levels of hormones with immune modifying properties, such as cortisol or inflammatory cytokines, may provide an advantageous period for vaccination responses to occur, their levels were analyzed at baseline to identify relationships with antibody responses (Vaccine. 2016 May;34[24]:2679-85. doi: 10.1016/j.vaccine.2016.04.032 ).

The study results indicated significant effects of time of day on the A/H1N1 and B strain antibody responses, but not for the A/H3N2 strain. More specifically, morning vaccinations produced greater antibody responses for the A/H1N1 and B strains as compared with those vaccinated in the afternoon, while the A/H3N2 strain antibody responses did not differ between morning and afternoon administration. Furthermore, both men and women were equally likely to show these effects.

Given their known diurnal rhythms, expected significant differences between groups were found for cortisol, the cortisol:cortisone ratio, corticosterone, dehydroepiandrosterone (DHEA), and androstenedione. However, none of the measured steroid hormone or cytokine levels showed any relationship between the time of day and antibody responses.

Dr. Phillips and her associates said that the strength of their study was its first-of-a-kind, large-scale randomized design for the assessment of different times of vaccination, which provided evidence for the enhancement of the antibody responses to the influenza vaccine following morning administration. Limitations included the inability to reach the recruitment goal of 400 participants over three years, which may have reduced the statistical power of the study.

The study was funded by a Medical Research Council Lifelong Health and Wellbeing Collaborative Research Grant to the University of Birmingham. The authors declared no conflicts of interest.

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