Brown, Michaela
(2022)
Don’t worry, be happy: enhancing the positive mood of older adults and investigating influenza vaccination responses.
PhD thesis, University of Nottingham.
Abstract
Vaccinations are vital for reducing the risk of disease, where they play an important role in combating influenza. However, some populations, such as older adults (≥65 years), respond poorly to influenza vaccination due to their compromised immune systems, with efficacy at 17-53% compared to 70-90% in young adults. This is a phenomenon referred to as immunosenescence, whereby older adults have sub-optimal immune systems and are therefore more susceptible to infectious disease. The burden of influenza is becoming an increasingly important challenge to tackle with the rapidly ageing population in the UK. Every year the UK experiences 4,000 to 14,000 deaths due to influenza, where a staggering 90% of these are older adults.
Pharmaceutical avenues have been explored to improve vaccination, such as the addition of vaccine adjuvants, in the hope that individuals will present greater immune responses and, in turn, improve vaccine effectiveness. Pharmaceutical methods have been proven to improve vaccine efficacy. However, they have not improved the immune responses of older adults to the same degree as young adults, therefore highlighting the need for alternative methods to improve vaccine effectiveness for this vulnerable population. Psychological effects, such as mood, loneliness and depression have been identified as immune modulators, where they have been observed to alter immune responses in a variety of ways. Previous research has also demonstrated that psychological interventions are capable of altering these psychological factors to influence immune responses, such as antibody responses to vaccination. This has highlighted the potential for psychological interventions to be used within a clinical setting to improve the vaccination outcomes of older adults. A previous pilot study (n= 138) demonstrated the use of a brief positive mood intervention (standardised, fixed-content intervention) to be effective at enhancing the positive mood of older adults immediately prior to influenza vaccination. In addition, previous research has shown interventions that permit a degree of choice for the participant can result in increased engagement and interest and therefore suggests they could be more effective than non-choice interventions for altering psychological factors, such as positive mood.
This thesis presents a large, a three armed, parallel, randomisation control trial (n= 654), which aimed to build upon the body of research investigating positive mood and influenza vaccination responses in older adults. The primary aim of the Flu and Mood in Older Adults (For-ME) trial presented in this thesis was to determine whether a standardised (fixed-content) intervention and/or choice intervention were capable of improving the positive of older adults immediately prior to influenza vaccination, compared with usual care. A comparison between both intervention types was also carried out to determine whether the standardised or choice intervention was superior for improving positive mood. The secondary aim was to investigate antibody responses to vaccination to determine whether group allocation was a significant predictor of antibody responses to vaccination. Antibody responses to vaccination were measured via Enzyme-Linked Immunosorbent (ELISA) assay and Hemagglutinin Inhibition (HAI) assay and the findings from these two methods were explored and compared.
The research outlined in this thesis revealed that both brief psychological interventions were capable of improving the mood of older adults in a clinical setting, compared with usual care. Both positive mood interventions were equally effective at improving the mood of older adults prior to influenza vaccination. Thus, the provision of choice did not notably enhance the intervention’s impact on mood. Antibody responses 4-weeks post-vaccination were found to be robust with seroprotection rates of >80% for all three influenza vaccine strains and across all three arms of the trial. However, antibody responses to vaccination were found to not differ significantly differ between groups. It is concluded that, in the context of highly immunogenic adjuvanted vaccines, any impact of short interventions on subsequent peak antibody responses to influenza vaccination were potentially too small to be detected in the current trial.
Future directions for research can aim to build upon these findings to investigate whether positive mood is capable of acting on the immune system beyond antibody responses to vaccination by considering T cell responses. More importantly, an immune mechanism study is required to drive this area of research forward to gain insight into the types of immune responses altered in the context of positive mood.
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