Background The COVID-19 pandemic has had a profound impact on the mental health of people worldwide. Mental health also impacts on physical health. In the context of viral illnesses, viral challenge studies have shown that indices of mental health are associated with susceptibility to viral infections, including coronaviruses. Research conducted during the pandemic has shown that people with a history of mental health conditions were at increased risk of infection, hospitalisation, and mortality. However, the relationship between mental health conditions and vaccine outcomes such as vaccine intentions, uptake, and vaccine breakthrough is not yet well-understood.

Methods We conducted a systematic search on the topics of COVID-19 vaccine intentions, vaccine uptake, and vaccine breakthrough, in relation to mental health conditions, in four databases: PubMed, MEDLINE, SCOPUS, and PsychINFO, as well as the publication lists of Clinical Practice Research Datalink (CPRD), The Health Improvement Network (THIN), OpenSAFELY, and QResearch. Inclusion criteria focus on studies reporting either of the aforementioned COVID-19 vaccine outcomes among people with mental health conditions.

Results Thirty-three out of 251 publications met our inclusion criteria for this review. Overall, the evidence is inconclusive regarding the level of intention to accept the COVID-19 vaccine among people with mental health conditions. However, people with mental health conditions were more likely to have lower uptake of the COVID-19 vaccine, compared to people without. Common barriers to COVID-19 vaccine uptake include concerns about the safety, effectiveness, and side effects of the vaccines. Limited evidence also suggests that vaccine breakthrough may be a particular risk for those with substance use disorder.

Conclusions Our findings revealed a possible intention-behaviour gap for receiving the COVID-19 vaccine among people with mental health conditions, yielding interventions to encourage vaccine uptake in this population. There is also the need to enhance our understanding of COVID-19 vaccine breakthrough in people with mental health conditions.

The authors have declared no competing interest.

This work was supported by the National Institute for Health Research School for Primary Care Research (NIHR SPCR) [Grant Reference Number: C044, 615]. RJ acknowledges the financial support of the National Institute for Health and Care Research (NIHR) Oxford Health Biomedical Research Centre (BRC). CC acknowledges support from the NIHR Nottingham Biomedical Research Centre. This manuscript reflects preliminary work relating to UK Longitudinal Linkage Collaboration (UK LLC) project LLC_0027 and UK LLC funding from the UKRI funded Longitudinal Health and Wellbeing National Core Study led by University College London (Grant code MC_PC_20059); and UK LLC's UKRI core funding (MR/X021556/1 and ES/X000567/1) supported ET's contribution. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. No other funding supported the work described in this manuscript.

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