Gerjo Kok

Prof. Gerjo Kok

orcid

Research Focus & Metrics

Academic Career Length

37Years (1990-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
15 October 2015 in Health Psychology Review
Verified
Journal Article
Open access
GKGerjo Kok
Gerjo Kok
NGNell H. Gottlieb
Nell H. Gottlieb
GPGjalt-Jorn Y. Peters
Gjalt-Jorn Y. Peters
PMPatricia Dolan Mullen
Patricia Dolan Mullen
GPGuy S. Parcel
Guy S. Parcel
LBL. Kay Bartholomew
L. Kay Bartholomew
In this paper, we introduce the Intervention Mapping (IM) taxonomy of behaviour change methods and its potential to be developed into a coding taxonomy. That is, although IM and its taxonomy of behaviour change methods are not in fact new, because IM was originally developed as a tool for intervention development, this potential was not immediately apparent. Second, in explaining the IM taxonomy and defining the relevant constructs, we call attention to the existence of parameters for effectiveness of methods, and explicate the related distinction between theory-based methods and practical applications and the probability that poor translation of methods may lead to erroneous conclusions as to method-effectiveness. Third, we recommend a minimal set of intervention characteristics that may be reported when intervention descriptions and evaluations are published. Specifying these characteristics can greatly enhance the quality of our meta-analyses and other literature syntheses. In conclusion, the dynamics of behaviour change are such that any taxonomy of methods of behaviour change needs to acknowledge the importance of, and provide instruments for dealing with, three conditions for effectiveness for behaviour change methods. For a behaviour change method to be effective: (1) it must target a determinant that predicts behaviour; (2) it must be able to change that determinant; (3) it must be translated into a practical application in a way that preserves the parameters for effectiveness and fits with the target population, culture, and context. Thus, taxonomies of methods of behaviour change must distinguish the specific determinants that are targeted, practical, specific applications, and the theory-based methods they embody. In addition, taxonomies should acknowledge that the lists of behaviour change methods will be used by, and should be used by, intervention developers. Ideally, the taxonomy should be readily usable for this goal; but alternatively, it should be clear how the information in the taxonomy can be used in practice. The IM taxonomy satisfies these requirements, and it would be beneficial if other taxonomies would be extended to also meet these needs.

3 January 2011 in BMC Public Health
Verified
Journal Article
Open access
PDF file
MBMarloes Bults
Marloes Bults
DBDesirée Jma Beaujean
Desirée Jma Beaujean
OZOnno de Zwart
Onno de Zwart
GKGerjo Kok
Gerjo Kok
PEPepijn van Empelen
Pepijn van Empelen
HVHélène Acm Voeten
Hélène Acm Voeten
Research into risk perception and behavioural responses in case of emerging infectious diseases is still relatively new. The aim of this study was to examine perceptions and behaviours of the general public during the early phase of the Influenza A (H1N1) pandemic in the Netherlands. Two cross-sectional and one follow-up online survey (survey 1, 30 April-4 May; survey 2, 15-19 June; survey 3, 11-20 August 2009). Adults aged 18 years and above participating in a representative Internet panel were invited (survey 1, n = 456; survey 2, n = 478; follow-up survey 3, n = 934). Main outcome measures were 1) time trends in risk perception, feelings of anxiety, and behavioural responses (survey 1-3) and 2) factors associated with taking preventive measures and strong intention to comply with government-advised preventive measures in the future (survey 3). Between May and August 2009, the level of knowledge regarding Influenza A (H1N1) increased, while perceived severity of the new flu, perceived self-efficacy, and intention to comply with preventive measures decreased. The perceived reliability of information from the government decreased from May to August (62% versus 45%). Feelings of anxiety decreased from May to June, and remained stable afterwards. From June to August 2009, perceived vulnerability increased and more respondents took preventive measures (14% versus 38%). Taking preventive measures was associated with no children in the household, high anxiety, high self-efficacy, more agreement with statements on avoidance, and paying much attention to media information regarding Influenza A (H1N1). Having a strong intention to comply with government-advised preventive measures in the future was associated with higher age, high perceived severity, high anxiety, high perceived efficacy of measures, high self-efficacy, and finding governmental information to be reliable. Decreasing trends over time in perceived severity and anxiety are consistent with the reality: the clinical picture of influenza turned out to be mild in course of time. Although (inter)national health authorities initially overestimated the case fatality rate, the public stayed calm and remained to have a relatively high intention to comply with preventive measures.

28 December 2017 in Health Psychology Review
Verified
Journal Article
Open access
GKGerjo Kok
Gerjo Kok
GPGjalt-Jorn Y. Peters
Gjalt-Jorn Y. Peters
LKLoes T. E. Kessels
Loes T. E. Kessels
Gill Ten HoorGill Ten Hoor
Gill Ten Hoor
RRRob Ruiter
Rob Ruiter
Use of fear appeals assumes that when people are emotionally confronted with the negative effects of their behaviour they will change that behaviour. That reasoning is simple and intuitive, but only true under specific, rare circumstances. Risk perception theories predict that if people will experience a threat, they want to counter that threat. However, how they do so is determined by their coping efficacy level: if efficacy is high, they may change their behaviour in the suggested direction; if efficacy is low, they react defensively. Research on fear appeals should be methodologically sound, comparing a threatening to a non-threatening intervention under high and low efficacy levels, random assignment and measuring behaviour as outcome. We critically review extant empirical evidence and conclude that it does not support positive effects of fear appeals. Nonetheless, their use persists and is even promoted by health psychology researchers, causing scientific insights to be ignored or misinterpreted.

16 December 2013 in BMC Public Health
Verified
Journal Article
Open access
PDF file
IHIrene A Harmsen
Irene A Harmsen
LMLiesbeth Mollema
Liesbeth Mollema
RRRob Ruiter
Rob Ruiter
TPTheo Gw Paulussen
Theo Gw Paulussen
HMhester de melker
hester de melker
GKGerjo Kok
Gerjo Kok
In high income countries, vaccine-preventable diseases have been greatly reduced through routine vaccination programs. Despite this success, many parents question, and a small proportion even refuse vaccination for their children. As no qualitative studies have explored the factors behind these decisions among Dutch parents, we performed a study using online focus groups. In total, eight online focus groups (n = 60) which included Dutch parents with at least one child, aged 0–4 years, for whom they refused all or part of the vaccinations within the National Immunization Program (NIP). A thematic analysis was performed to explore factors that influenced the parents’ decisions to refuse vaccination. Refusal of vaccination was found to reflect multiple factors including family lifestyle; perceptions about the child’s body and immune system; perceived risks of disease, vaccine efficacy, and side effects; perceived advantages of experiencing the disease; prior negative experience with vaccination; and social environment. The use of online focus groups proved to be an effective qualitative research method providing meaningful data. Information provided by the NIP turned out to be insufficient for this group of parents. More trust in the NIP and deliberate decisions might result from increased parental understanding of lifestyle and disease susceptibility, the impact of vaccinations on the immune system, and the relative risks of diseases and their vaccines. The public health institute should also inform parents that the NIP is recommended but non-mandatory.

26 May 2015 in Journal of Medical Internet Research
Verified
Journal Article
Open access
LMLiesbeth Mollema
Liesbeth Mollema
IHIrene Anhai Harmsen
Irene Anhai Harmsen
EBEmma Broekhuizen
Emma Broekhuizen
RCRutger Clijnk
Rutger Clijnk
HMhester de melker
hester de melker
EDEnny Das
Enny Das
Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet

1 March 2016 in Vaccine
Verified
Journal Article
Open access
BLBirthe A Lehmann
Birthe A Lehmann
GCGretchen B Chapman
Gretchen B Chapman
FFFrits Me Franssen
Frits Me Franssen
GKGerjo Kok
Gerjo Kok
RRRob Ruiter
Rob Ruiter
The prevention of health care acquired infections is an important objective for patient safety and infection control in all health care settings. Influenza vaccination uptake among health care workers (HCWs) is the most effective method to prevent transmission to patients, but vaccination coverage rates are low among HCWs. Several educational campaigns have been developed to increase the influenza vaccination coverage rates of HCWs, but showed only small effects. The aim of this study was to test an opt-out strategy in promoting uptake among HCWs in a tertiary care center for patients with complex chronic organ failure. HCWs were randomly assigned to one of two conditions. In the opt-out condition (N=61), participants received an e-mail with a pre-scheduled appointment for influenza vaccination, which could be changed or canceled. In the opt-in condition (N=61), participants received an e-mail explaining that they had to schedule an appointment if they wanted to get vaccinated. The findings show no statistically detectable effect of condition on being vaccinated against influenza. However, HCWs in the opt-out condition were more likely to have an appointment for influenza vaccination, which in turn increased the probability of getting vaccinated. To change the default to promote influenza vaccination among HCWs might be an easy and cost-effective alternative to the complex vaccination campaigns that have been proposed in recent years.