What is the aim of this review?
Vaccines are important for reducing the spread of infectious diseases during a pandemic such as COVID-19. Clinical trials test these vaccines to make sure that they are safe and effective. But it can be challenging to find enough people who are willing to take part in a vaccine trial for a pandemic or epidemic disease.
The aim of this Cochrane Review of qualitative research (or 'qualitative evidence synthesis') was to find out what influences a person's decision to take part in a vaccine trial in the context of a pandemic or epidemic. Understanding the factors that influence a person's decision to participate in a vaccine trial can inform trial design and development of recruitment strategies that optimise communication, informed consent, and participant inclusion and diversity in vaccine clinical trials. To answer the review question, we analysed 34 studies of people's views and experiences of taking part in a vaccine trial.
Key messages
Many factors influence a person's decision to take part in a vaccine trial during a pandemic or epidemic. People are influenced by the way in which the trial is set up and how information about the trial is communicated. People are also influenced by what they think the possible risks and side effects are. Friends and family may also have influenced their decision. A fear of stigma and distrust in governments may prevent people from taking part in a vaccine trial. People may often see the chance to help others and prevent the spread of disease as a reason to take part in a vaccine trial.
What did we find?
We included 34 studies that looked at people's views and experiences of being invited to take part in a vaccine trial in the context of a pandemic or epidemic. Most of the studies related to HIV vaccine trials. The other studies related to Ebola virus, tuberculosis, Zika virus and COVID-19. Studies were set in many countries across Africa, Asia, Europe and North America. The studies looked at the views and experiences of adults aged 18 years and over who had been invited to take part in vaccine clinical trials. Some of them had accepted and some had decided not to take part.
Main results
We identified several factors that people consider when deciding whether to take part in a vaccine trial during a pandemic or epidemic. We judged our confidence in these findings to be low, moderate or high depending on how well supported that finding was from the included studies. We had moderate to high confidence in most of the findings.
Some of the factors that influenced people's decisions were under the control of the team setting up the trial. For instance, people were influenced by how trial information was communicated, and whether community members were involved in information delivery. They were also influenced by how easy or convenient it was to take part in the trial, whether they would be paid to take part and whether they would get access to additional support or health services.
Other factors included personal concerns, and the influence of family and friends and wider society. From a personal point of view, people had concerns about vaccine side effects, how well the vaccine works, and how taking part in the trial might impact on their daily lives and responsibilities. People were also influenced by their families and whether taking part might affect their relationships with others. Some people feared stigma from their communities if they took part. People's level of trust in the government's involvement in research and trials could also influence their decisions.
People also considered the possible rewards of taking part in a trial and whether these outweighed the risks. Some of these rewards were personal. People wanted to get faster access to a vaccine, improve their health, improve their understanding of the disease and return to normal life during a pandemic or epidemic. But people were also motivated by wanting to help society and contribute to science. This was often tied to memories of family and friends who had died from the disease.
What are the limitations of the evidence?
We identified 34 studies for this review, but 26 were related to HIV. This raised concerns about the relevance of the data to other diseases. In addition, we had concerns about the quality of the data for some findings. Because of the diversity of the participants in individual studies, we cannot make any inferences by participant types (for example, participants' backgrounds, gender, or social standing or class).
How up-to-date is this evidence?
This review includes studies published before the end of June 2021.
This review identifies many of the factors that influence a person's decision to take part in a vaccine trial, and these reflect findings from reviews that examine trials more broadly. However, we also recognise some factors that become more important in connection with a vaccine trial in the context of a pandemic or epidemic. These factors include the potential stigma of taking part, the possible adverse effects of a vaccine, the added motivation for helping society, the role of community leaders in trial dissemination, and the level of trust placed in governments and companies developing vaccines. These specific influences need to be considered by trial teams when designing, and communicating about, vaccine trials in the context of a pandemic or epidemic.
The World Health Organization declared the COVID-19 pandemic on 11 March 2020. Vaccine development and deployment were swiftly prioritised as a method to manage and control disease spread. The development of an effective vaccine relies on people's participation in randomised trials. Recruitment to vaccine trials is particularly challenging as it involves healthy volunteers who may have concerns around the potential risks and benefits associated with rapidly developed vaccines.
To explore the factors that influence a person's decision to participate in a vaccine trial in the context of a pandemic or epidemic.
We used standard, extensive Cochrane search methods. The latest search date was June 2021.
We included qualitative studies and mixed-methods studies with an identifiable qualitative component. We included studies that explored the perspectives of adults aged 18 years or older who were invited to take part in vaccine trials in the context of a pandemic or epidemic.
We assessed the title, abstracts and full texts identified by the search. We used a sampling frame to identify data-rich studies that represented a range of diseases and geographical spread. We used QSR NVivo to manage extracted data. We assessed methodological limitations using an adapted version of the Critical Skills Appraisal Programme (CASP) tool for qualitative studies. We used the 'best-fit framework approach' to analyse and synthesise the evidence from our included studies. We then used the Confidence in the Evidence from Reviews of Qualitative research (GRADE-CERQual) assessment to assess our confidence in each finding and develop implications for practice.
We included 34 studies in our review. Most studies related to HIV vaccine trials. The other studies related to Ebola virus, tuberculosis, Zika virus and COVID-19. We developed 20 key findings, under three broad themes (with seven subthemes), that described the factors that people consider when deciding whether to take part in a vaccine trial for a pandemic or epidemic disease.
Our GRADE-CERQual confidence was high in nine of the key findings, moderate in 10 key findings and low in one key finding. The main reason for downgrading review findings were concerns regarding the relevance and adequacy of the underlying data. As a result of the over-representation of HIV studies, our GRADE-CERQual assessment of some findings was downgraded in terms of relevance because the views described may not reflect those of people regarding vaccine trials for other pandemic or epidemic diseases. Adequacy relates to the degree of richness and quantity of data supporting a review finding. Moderate concerns about adequacy resulted in a downgrading of some review findings.
Some factors were considered to be under the control of the trial team. These included how trial information was communicated and the inclusion of people in the community to help with trial information dissemination. Aspects of trial design were also considered under control of the trial team and included convenience of participation, provision of financial incentives and access to additional support services for those taking part in the trial.
Other factors influencing people's decision to take part could be personal, from family, friends or wider society. From a personal perceptive, people had concerns about vaccine side effects, vaccine efficacy and possible impact on their daily lives (carer responsibilities, work, etc.). People were also influenced by their families, and the impact participation may have on relationships. The fear of stigma from society influenced the decision to take part. Also, from a societal perspective, the level of trust in governments' involvement in research and trial may influence a person's decision.
Finally, the perceived rewards, both personal and societal, were influencing factors on the decision to participate. Personal rewards included access to a vaccine, improved health and improved disease knowledge, and a return to normality in the context of a pandemic or epidemic. Potential societal rewards included helping the community and contributing to science, often motivated by the memories of family and friends who had died from the disease.