Abstract

Objective:

To determine the effectiveness of a brief intervention in increasing influenza vaccination coverage compared with the usual advice in people who refuse it, and to record the main reasons for refusing to be vaccinated.

Method:

A cluster randomized clinical trial was conducted in which the study population was individuals with high risk factors who initially had refused to be vaccinated against influenza. Professionals (doctors and nurses) who voluntarily accepted to participate were assigned randomly to the intervention group (brief intervention) and the control group (usual advice).

Results:

57 professionals recruited 524 people who had previously declined the influenza vaccination (271 in the control group and 253 in the intervention group). Brief intervention showed its effectiveness with an odds ratio of 2.48 (1.61-3.82; p<0.001), in individuals aged 60 or over, both healthy or with risk factors. The most frequent reasons for rejection of vaccination were the belief that there was no risk of getting sick (53.0%) and the fear of the side effects (33.3%).

Conclusions:

Brief intervention is an effective tool in improving vaccination coverage in people who have initially rejected it.

Keywords:
Directive counselling; Health education; Influenza vaccines; Primary health care; Vaccination coverage

Resumen

Objetivo:

Determinar la efectividad del consejo breve para la vacunación antigripal frente al consejo habitual en personas que la rechazan, y conocer los principales motivos de rechazo.

Método:

Se realizó un ensayo clínico aleatorizado por clusters, en el que la población de estudio eran personas con factores de riesgo y que inicialmente rechazaban vacunarse. Los/las profesionales (médicos/as y enfermeros/as) que aceptaron participar se distribuyeron aleatoriamente en un grupo de intervención (consejo breve) y un grupo de control (consejo habitual).

Resultados:

Cincuenta y siete profesionales reclutaron 524 personas que rechazaron la vacunación (271 en el grupo control y 253 en el grupo de intervención). El consejo breve demostró su efectividad, con una odds ratio de 2,48 (1,61-3,82; p<0.001), en las personas de 60 años o más, sanos o con factores de riesgo. Los principales motivos para no vacunarse fueron la creencia de no estar en riesgo de enfermar (53,0%) y el miedo a los efectos secundarios (33,3%).

Conclusiones:

El consejo breve es una herramienta efectiva para mejorar las coberturas de vacunación en personas que la rechazan inicialmente.

Palabras clave:
Consejo dirigido; Educación sanitaria; Vacunas contra la gripe; Atención primaria de salud; Cobertura de vacunación

Introduction

Influenza is considered to be a serious public health problem, since it causes high morbidity rates during annual epidemics (between 5 and 20% in the general population).¹1. Agència de Salut Pública de Catalunya. Departament de Salut, Generalitat de Catalunya. Programa de vacunacions. Guia tècnica per a la campanya de vacunació antigripal estacional 2018. Campanya 2018-19. Barcelona: ASPCAT; 2018. p. 36. Available at: https://salutpublica.gencat.cat/ca/inici
https://salutpublica.gencat.cat/ca/inici... In addition, it can more severely affect people belonging to certain high-risk groups (such as those aged over 60, people with chronic conditions, pregnant women).¹1. Agència de Salut Pública de Catalunya. Departament de Salut, Generalitat de Catalunya. Programa de vacunacions. Guia tècnica per a la campanya de vacunació antigripal estacional 2018. Campanya 2018-19. Barcelona: ASPCAT; 2018. p. 36. Available at: https://salutpublica.gencat.cat/ca/inici
https://salutpublica.gencat.cat/ca/inici... World Health Organization has recently estimated that every year 290,000 to 650,000 deaths are associated with respiratory diseases from seasonal influenza.²2. Lee VJ, Ho ZJM, Goh EH, et al. Advances in measuring influenza burden of disease. Influenza Other Respir Viruses. 2018;12:3-9. In the region were the present study was carried out (Catalonia, Spain) mortality rates were 13.4% according to data from the 2017-2018 season, similar to previous years.³3. Agència de Salut Pública de Catalunya. Departament de Salut, Generalitat de Catalunya. Pla d'informació de les infeccions respiratòries agudes a Catalunya (PIDIRAC). Balanç temporada gripal 2017-2018. Barcelona: ASPCAT;; 2018. p. 13 [Accessed 7 January 2021]. Available at: https://scientiasalut.gencat.cat/handle/11351/4321.
https://scientiasalut.gencat.cat/handle/...

The inactivated influenza vaccine (IIV) is, alongside with hygiene measures, the main prevention strategy against influenza and its complications.¹1. Agència de Salut Pública de Catalunya. Departament de Salut, Generalitat de Catalunya. Programa de vacunacions. Guia tècnica per a la campanya de vacunació antigripal estacional 2018. Campanya 2018-19. Barcelona: ASPCAT; 2018. p. 36. Available at: https://salutpublica.gencat.cat/ca/inici
https://salutpublica.gencat.cat/ca/inici... The vaccine immune response is variable: in young and healthy people its effectiveness can be between 70 and 90% to prevent influenza. Between 30 and 70% of the hospitalization for influenza and pneumonia can be prevented by the IIV. In the elderly in institutional care, the classic inactivated virus vaccines have shown to have an effectiveness of between 50 and 60% to prevent hospitalization and pneumonia and 80% in preventing death from influenza.¹1. Agència de Salut Pública de Catalunya. Departament de Salut, Generalitat de Catalunya. Programa de vacunacions. Guia tècnica per a la campanya de vacunació antigripal estacional 2018. Campanya 2018-19. Barcelona: ASPCAT; 2018. p. 36. Available at: https://salutpublica.gencat.cat/ca/inici
https://salutpublica.gencat.cat/ca/inici...

Although IIV recommendation is widely practiced and accepted, vaccination coverage has remained relatively low. According to the Spanish Ministry of Health, IIV rates for people aged over 65 during the 20162017 campaign stood at 55.5% for Spain as a whole and 54.3% in Catalonia.⁴4. Ministerio de Sanidad, Consumo y Bienestar Social. Coberturas de vacunación. Datos estadísticos. [Accessed 7 January 2021]. Available at: https://www.mscbs.gob.es/profesionales/saludPublica/prevPromocion/vacunaciones/ calendario-y-coberturas/coberturas/docs/Todas_las_tablas2016.pdf.
https://www.mscbs.gob.es/profesionales/s...

Some studies in adults⁵5. Bish A, Yardley L, Nicoll A, et al. Factors associated with uptake of vaccination against pandemic influenza: a systematic review. Vaccine. 2011;29:6472-84.^,66. Giese C, Mereckiene J, Danis K, et al. Low vaccination coverage for seasonal influenza and pneumococcal disease among adults at-risk and health care workers in Ireland 2013 the key role of GPs in recommending vaccination. Vaccine. 2016;34:3657-62. have explored patients and doctors' reasons for deciding whether or not to get vaccinated against the influenza virus. These studies suggest that non-vaccinating patients mention the fear of adverse side effects, a fear of contracting the illness, a belief that they do not belong to a risk group or simply having never considered it. They mention doubts regarding efficacy and safety to a lesser extent.

According to Picazo et al.⁷7. Picazo J, González Romo F, Salleras Sanmartí J, et al. Encuesta sobre la vacunación de adultos en España. Gripe y neumococo. Vacunas. 2012;13:100-11. and Giese et al.⁶6. Giese C, Mereckiene J, Danis K, et al. Low vaccination coverage for seasonal influenza and pneumococcal disease among adults at-risk and health care workers in Ireland 2013 the key role of GPs in recommending vaccination. Vaccine. 2016;34:3657-62., the role of healthcare professionals is essential in increasing IIV coverage by providing patients over 18 with information and advice. Their opinion and example may influence patients' decisions one way or another. Certain beliefs and attitudes held by healthcare personnel influence their own vaccination rates and can prevent patients from receiving suitable health education.⁷7. Picazo J, González Romo F, Salleras Sanmartí J, et al. Encuesta sobre la vacunación de adultos en España. Gripe y neumococo. Vacunas. 2012;13:100-11.

The majority of patients who have been vaccinated have done so following the advice recommendation of their general practitioners, a specialist or a nurse. These patients include both adults over 60⁷7. Picazo J, González Romo F, Salleras Sanmartí J, et al. Encuesta sobre la vacunación de adultos en España. Gripe y neumococo. Vacunas. 2012;13:100-11. and children or adolescents under 18.⁸8. Stockwell MS, Kharbanda EO, Martinez RA, et al. Effect of a text messaging intervention on influenza vaccination in an urban, low-income pediatric and adolescent population: a randomized controlled trial. JAMA. 2012;307:1702-8. Patients typically voice their doubts regarding the vaccine and its potential side effects in the nursing or doctor's consulting room. 47% of patients who have not been vaccinated would be willing to do so if its necessity was explained to them thoroughly enough.⁷7. Picazo J, González Romo F, Salleras Sanmartí J, et al. Encuesta sobre la vacunación de adultos en España. Gripe y neumococo. Vacunas. 2012;13:100-11.

Numerous strategies have been tried in an attempt to promote vaccinations and increase coverage: text messages containing advice, reminders, telephone calls, and interventions such as brief education.⁶6. Giese C, Mereckiene J, Danis K, et al. Low vaccination coverage for seasonal influenza and pneumococcal disease among adults at-risk and health care workers in Ireland 2013 the key role of GPs in recommending vaccination. Vaccine. 2016;34:3657-62.

7. Picazo J, González Romo F, Salleras Sanmartí J, et al. Encuesta sobre la vacunación de adultos en España. Gripe y neumococo. Vacunas. 2012;13:100-11.

8. Stockwell MS, Kharbanda EO, Martinez RA, et al. Effect of a text messaging intervention on influenza vaccination in an urban, low-income pediatric and adolescent population: a randomized controlled trial. JAMA. 2012;307:1702-8.^-99. European Centre for Disease Prevention and Control. Catalogue of interventions addressing vaccine hesitancy. Stockholm: ECDC; 2017. p. 71. Available at: https://www.ecdc.europa.eu/sites/default/files/documents/Catalogueinterventions-vaccine-hesitancy.pdf.
https://www.ecdc.europa.eu/sites/default... According to a review by the European Centre for Disease Prevention and Control (ECDC),⁹9. European Centre for Disease Prevention and Control. Catalogue of interventions addressing vaccine hesitancy. Stockholm: ECDC; 2017. p. 71. Available at: https://www.ecdc.europa.eu/sites/default/files/documents/Catalogueinterventions-vaccine-hesitancy.pdf.
https://www.ecdc.europa.eu/sites/default... some of these strategies have not yet been evaluated, while others have shown a degree of effectiveness, especially in changing attitudes and beliefs regarding vaccination.

Brief intervention is a method involving the delivery of health education in a direct, personalized, short way (lasting between 3 and 15minutes),¹⁰10. Organización Mundial de la Salud. Intervención breve vinculada a ASSIST para el consumo riesgoso y nocivo de sustancias. Manual para uso en atención primaria. Ginebra: Organización Mundial de la Salud; 2011. p. 45. Available at: https://apps.who.int/iris/bitstream/handle/10665/85401/9789275332344spa.pdf?sequence=1&isAllowed=y.
https://apps.who.int/iris/bitstream/hand...

11. Institut Català de la Salut. Detecció i tractament del consum del tabac. Guies de pràctica clínica. Barcelona: Institut Català de la Salut. Generalitat de Catalunya; 2009. 63 p. Available at: http://ics.gencat.cat/web/.content/documents/assistencia/gpc/guia_tabac.pdf.
http://ics.gencat.cat/web/.content/docum...

12. Raw M, Anderson P, Batra A, et al. WHO Europe evidence based recommendations on the treatment of tobacco dependence. Tobacco Control. 2002;11:44-6.^-1313. Whitlock E, Orleans C, Pender N, et al. Evaluating primary care behavioral counseling interventions An evidence-based approach. Am J Prev Med. 2002;22:267-84. which is systematic, universal, structured and integrated into daily clinical practice. In the case of the influenza vaccination, this is an opportunistic recommendation from the healthcare professional to patients in high-risk groups. brief intervention is effective in increasing vaccination coverage rates for various vaccines and different population groups¹⁴14. Wong VW, Fong DY, Tarrant M. Brief education to increase uptake of influenza vaccine among pregnant women: a study protocol for a randomized controlled trial. BMC Pregnancy Childbirth. 2014;14:1-7.

15. Wong VW, Wong Y, Yee D, et al. Brief education to promote maternal influenza vaccine uptake: a randomized controlled trial. Vaccine. 2016;34:5243-50.

16. Ferguson PE, Jordens CF, Gilroy NM. Patient and family education in HSCT: improving awareness of respiratory virus infection and influenza vaccination. A descriptive study and brief intervention. Bone Marrow Transplant. 2010;45:656-61.

17. Chan SS, Leung DY, Leung AY, et al. A nurse-delivered brief health education intervention to improve pneumococcal vaccination rate among older patients with chronic diseases: a cluster randomized controlled trial. Int J Nurs Stud. 2015;52:317-24.^-1818. Bonafide KE, Vanable PA. Male human papillomavirus vaccine acceptance is enhanced by a brief intervention that emphasizes both male-specific vaccine benefits and altruistic motives. Sex Transm Dis. 2015;42:76-80.: influenza vaccine in pregnant women or adults with chronic diseases, anti-pneumococcal in seniors and high risk groups, human papillomavirus vaccine in young males, among others.

Therefore, during the 2016-2017 vaccination campaign, a previous pilot study¹⁹19. Muñoz-Miralles R, Bonvehí Nadeu S, Sant Masoliver C, et al. Efectividad del consejo breve en la vacunación contra la gripe Estudio piloto en atención primaria. Vacunas. 2019;20:18-24. was carried out at an urban health centre to evaluate the effectiveness of a brief, structured, standardized education intervention which directly addressed the reasons for rejection expressed by patients. This study proved to be effective, although the sample was small and not randomized, so it was recommended to carry out a larger and randomized study.

The general objective was to determine the effectiveness of the use of brief intervention for the inactivated influenza vaccine compared to the usual advice, in people who refuse to be vaccinated.

Specific objectives:

Method

A cluster randomized controlled clinical trial.

The reference population consisted of patients assigned to and treated by urban and rural health centres in the centre of Catalonia, an area with a population of approximately 405,000. 135,648 were the risk factor population that could be vaccinated against influenza virus.

The study population consisted of individuals in healthcare centres during the 2017 influenza campaign. They were members of risk groups for IIV (older than 60 and healthy, under and over 60 and at risk of further complications resulting from influenza).²2. Lee VJ, Ho ZJM, Goh EH, et al. Advances in measuring influenza burden of disease. Influenza Other Respir Viruses. 2018;12:3-9.

Inclusion criteria:

Exclusion criteria:

The Research Ethics Committee of the Institut Universitari d'Investigació en Atenció Primària (IDIAP Jordi Gol) approved the study protocol (P17/224).

After an email inviting all professionals in the area (905 from 32 primary care centers) to participate in the study, they were able to voluntarily decide whether or not to participate. The participants (doctors and nurses) from the different centres were randomly assigned by clusters to either the intervention group (IG) or the control group (CG) made up of 27 and 30 professionals, respectively. It was taken into account that if a doctor and a nurse who participated, were working as a team with the same assigned patients, they both participated in the same control or intervention group. All professionals who participated attended a general meeting where the study was explained; then specific instructions were given to the professionals in the CG, and finally, and only in the presence of the professionals from the IG, the brief intervention was explained in detail.

The recruitment of patients suitable to participate in the study was carried out during the IIV campaign, as part of the health centre's routine activities. Patients with inclusion criteria who came to see a doctor or nurse were invited to participate in the study. Those who accepted participating signed an informed consent.

In the IG, patients were asked about the reasons to reject the IIV and they were recorded on an Excel document. The intervention consisted of a standardized brief intervention, which varied depending on the reason the patient had given for refusing the vaccination. The advice was created following a literature search for articles, which included patient surveys to determine reasons for rejection of IIV or similar vaccines. The main reasons for rejection were divided into groups and the arguments against them were based on scientific data in order to rebut said arguments and encourage a favourable and more informed decision. Brief intervention was performed by the healthcare professional during the consultation. It was given verbally, with written support (Table 1). The reasons for non-vaccination were only collected in the IG, because it was necessary for the intervention.

In the CG the IIV advice didn't change: it was the normal advice that professionals used to give their patients, that is, any unstructured advice on IIV performed by the health professional, that they do every year during influenza vaccination campaigns. Patients in the CG were not asked for the reasons for the rejection of the vaccine to prevent them from influencing the advice.

There were no known differences between the advice given by a doctor or a nurse: in the CG was used the usual advice, and in the IG the brief intervention. Groups were selected including both types of professionals in both groups to avoid differences between groups.

Data was collected anonymously and confidentially via the electronic health record of Catalonia [eCAP in Catalan]. The variables analysed for the two groups were: IIV at the end of the 2017 vaccination campaign (yes/no), age, IIV risk factors and reasons for non-vaccination.

The SPSS v18 statistical program was used to analyse the data. IIV coverage was recorded for the CG and IG as a whole and for each risk group. The analysis of any statistical differences between the control and intervention groups was conducted using the chi-square test, with a p value<0.05 considered statistically significant.

Results

57 professionals from 18 different primary care centers voluntarily participated in this study.

Of a sample of 524 patients belonging to a high-risk group for IIV who did not intend to be vaccinated, 251 belonged to the IG and 273 to the CG.

Of the sample obtained, 40.1% (n=210) of the patients were 60 or older and healthy, 44.5% (n=233) were 60 or over 60 with some risk factors and 10.9% (n=57) younger than 60 with risk factors (1.3% were paediatric patients, n=7). 4.6% of patients (n=24) were at risk of IIV but with risk factors, which did not appear on the eCAP list (Table 2).

Vaccination coverage in these patients (who had rejected the IIV, but who were part of a high-risk group) was 21.9% (n=115): 24.3% of those 60 or over 60 who were healthy, 18.9% of patients 60 or over 60 with various risk factors and 24.6% of those under the age of 60 with risk factors.

The main risk factors of patients who initially rejected the vaccine but were finally vaccinated were metabolic (25.4%), kidney (17.9%), cardiovascular (17.4%) or pulmonary (13.0%) disease (Table 3). There were no statistically significant differences in the vaccination according to which one of the risk factors.

The main reasons for not getting vaccinated, in both age groups, were “I never get sick” (53.0%) and “It has side effects” (33.3%). The least frequent motive was “They (the pharmaceutical industry) do it for the money” (0.4%) (Table 4). 17 results were lost due to incorrect registration.

At the end of the IIV campaign, 75 patients (29.9%) in the IG were vaccinated and 40 in the CG (14.6%). The intervention was effective at the global level (odds ratio [OR]: 2.48 [1.61-3.82]; p<0.001) and in those aged 60 and over 60 (healthy OR: 2.62 [1.32-5.17], and with risk factors OR: 2.95 [1.495.79]). There were no statistically significant differences in the effectiveness of the intervention in those aged under 60 with risk factors or between individuals with different illnesses (Table 2).

Discussion

The results obtained in this study show that IIV coverage in patients with vaccine hesitancy continues to remain low, in all groups. In order to increase vaccination coverage, there is a clear need to develop measures aimed at achieving changes in attitudes and certain behaviours,¹³13. Whitlock E, Orleans C, Pender N, et al. Evaluating primary care behavioral counseling interventions An evidence-based approach. Am J Prev Med. 2002;22:267-84. in the same way other behaviours which have a negative impact on health are addressed.

The present study raises the possibility of improving the coverage of IIV with a low-cost intervention, which is easily incorporated into a primary healthcare professional's routine, by means of brief intervention lasting 2-5minutes, something that is practicable on a daily basis.

Our study suggests that a structured brief intervention in influenza vaccine, as in studies conducted with other vaccines,¹²12. Raw M, Anderson P, Batra A, et al. WHO Europe evidence based recommendations on the treatment of tobacco dependence. Tobacco Control. 2002;11:44-6.

13. Whitlock E, Orleans C, Pender N, et al. Evaluating primary care behavioral counseling interventions An evidence-based approach. Am J Prev Med. 2002;22:267-84.

14. Wong VW, Fong DY, Tarrant M. Brief education to increase uptake of influenza vaccine among pregnant women: a study protocol for a randomized controlled trial. BMC Pregnancy Childbirth. 2014;14:1-7.

15. Wong VW, Wong Y, Yee D, et al. Brief education to promote maternal influenza vaccine uptake: a randomized controlled trial. Vaccine. 2016;34:5243-50.^-1616. Ferguson PE, Jordens CF, Gilroy NM. Patient and family education in HSCT: improving awareness of respiratory virus infection and influenza vaccination. A descriptive study and brief intervention. Bone Marrow Transplant. 2010;45:656-61. is very effective in improving IIV rates, especially in those patients aged over 60, regardless of whether they are in a high-risk group for contracting influenza.

According to Nyhan and Reifler²⁰20. Nyhan B, Reifler J. Does correcting myths about the influenza vaccine work? An experimental evaluation of the effects of corrective information. Vaccine. 2015;33:459-64., and the ECDC⁹9. European Centre for Disease Prevention and Control. Catalogue of interventions addressing vaccine hesitancy. Stockholm: ECDC; 2017. p. 71. Available at: https://www.ecdc.europa.eu/sites/default/files/documents/Catalogueinterventions-vaccine-hesitancy.pdf.
https://www.ecdc.europa.eu/sites/default... , overcoming myths and mistaken beliefs in relation to vaccines may not be sufficient to improve immunization rates. In the present study, brief intervention has been shown to be effective in individuals with vaccine hesitancy. However, it is equally important that each case is dealt with on an individual basis in order to provide them with suitable information so that individuals can make an informed decision.

The implementation of this intervention in primary care could be very useful in health management and have a big impact. This measure would be a valid and effective tool for recommending vaccination to patients with vaccine hesitancy and thus increase vaccination coverage, something that numerous organizations and health institutions declare to be a priority every flu season.¹1. Agència de Salut Pública de Catalunya. Departament de Salut, Generalitat de Catalunya. Programa de vacunacions. Guia tècnica per a la campanya de vacunació antigripal estacional 2018. Campanya 2018-19. Barcelona: ASPCAT; 2018. p. 36. Available at: https://salutpublica.gencat.cat/ca/inici
https://salutpublica.gencat.cat/ca/inici...

Certainly, in some cases, using the brief intervention is not enough to get them vaccinated against the flu. For this reason it's very important to use the different tools available. There are also experiences with phone calls, reminder letters, on-going recommendations, or sending short text messages (SMS)⁶6. Giese C, Mereckiene J, Danis K, et al. Low vaccination coverage for seasonal influenza and pneumococcal disease among adults at-risk and health care workers in Ireland 2013 the key role of GPs in recommending vaccination. Vaccine. 2016;34:3657-62.

7. Picazo J, González Romo F, Salleras Sanmartí J, et al. Encuesta sobre la vacunación de adultos en España. Gripe y neumococo. Vacunas. 2012;13:100-11.

8. Stockwell MS, Kharbanda EO, Martinez RA, et al. Effect of a text messaging intervention on influenza vaccination in an urban, low-income pediatric and adolescent population: a randomized controlled trial. JAMA. 2012;307:1702-8.^-99. European Centre for Disease Prevention and Control. Catalogue of interventions addressing vaccine hesitancy. Stockholm: ECDC; 2017. p. 71. Available at: https://www.ecdc.europa.eu/sites/default/files/documents/Catalogueinterventions-vaccine-hesitancy.pdf.
https://www.ecdc.europa.eu/sites/default... . For example, the simple reminder via SMS to the high risk population, makes it possible to increase the vaccination rate, especially in children under 5 and pregnant women. It is also recognized that the content of the SMS is important and better results are found when educational and information elements are included in the message, and not just a reminder of the need to be vaccinated.⁹9. European Centre for Disease Prevention and Control. Catalogue of interventions addressing vaccine hesitancy. Stockholm: ECDC; 2017. p. 71. Available at: https://www.ecdc.europa.eu/sites/default/files/documents/Catalogueinterventions-vaccine-hesitancy.pdf.
https://www.ecdc.europa.eu/sites/default... ^,2121. Regan AK, Bloomfield L, Peters I, Effler PV. Randomized controlled trial of text message reminders for increasing Influenza vaccination. An Fam Med. 2017;15:507-14.

Professionals who voluntarily participated were motivated professionals for the influenza vaccination campaign and to give and to improve their advice. The use of a cluster randomised trial for the intervention/control groups eliminated a possible selection bias, which was present in the pilot study,¹⁹19. Muñoz-Miralles R, Bonvehí Nadeu S, Sant Masoliver C, et al. Efectividad del consejo breve en la vacunación contra la gripe Estudio piloto en atención primaria. Vacunas. 2019;20:18-24. thus consolidating the results obtained. To minimize a possible bias and to prevent from influencing the usual advice in the CG, the professionals in this group didn't know the brief intervention and how to develop it. In the primary care setting, different methods are used to give advice, although they were not controlled here. However, the present study has verified the impact of the brief intervention carried out by health professionals on the vaccination rates of the intervention group.

Furthermore, perhaps there could be a convenience bias as patients were recruited as they went to the health center. In future research, possible randomization should be considered.

In comparison with the strength of similar methods assessed in a meta-analysis of 61 trials,²²22. Thomas RE, Lorenzetti DL. Interventions to increase influenza vaccination rates of those 60 years and older in the community. Cochrane Database Syst Rev. 2018:CD005188. the current study also reveals a high OR. But the difference with other studies is the inclusion of patients who initially rejected the vaccine.

The present study included paediatric patients in the sample, since it was decided that brief intervention could also prove effective in this group. Nevertheless, the sample of patients in this subgroup was small and they could not be analysed as an independent group.

Future research should be directed to the study of brief intervention's effectiveness in people with illnesses, which were poorly represented in the sample, such as neoplasms, hemoglobinopathies or those who were immunosuppressed. It would also be interesting to specifically explore their effectiveness in other groups who are in a high-risk group for contracting influenza, such as healthcare professionals, caregivers, pregnant women or essential workers (like police officers, fire-fighters, etc)., and to explore other methods to improve vaccination in young people with risk factors, where there is no important advantage with the brief intervention. Finally, it would also be important in future research to make an effort to train professionals before and during the brief intervention.

Conclusions

Brief intervention is an effective, low cost and easy-to-use tool for health professionals that can change attitudes, beliefs and behaviour, thus achieving an improvement in influenza vaccination coverage. Main reasons for not getting vaccinated were the perception of never getting sick and fear to side effects.

Future research ought to be directed towards evaluating the application of this measure in other population groups and illnesses.

Transparency declaration

The corresponding author on behalf of the other authors guarantee the accuracy, transparency and honesty of the data and information contained in the study, that no relevant information has been omitted and that all discrepancies between authors have been adequately resolved and described.

Acknowledgements

This study has been made possible thanks to the collaboration of the primary health care doctors and nurses: Javier Aibar, Alicia Ariño, Joan Armengol, Ester Arnau, Cristina Ayala, Anna Aymerich, Marta Barrufet, Montserrat Belmonte, M. Dolors Circuns, Rosa Cirera, Montserrat Ciurana, Eva Codinach, Engràcia Atienza, Anna Crespiera, Concepció Espinós, Anna M. Ferrer, Francisca Garcia, Montse Girbau, Anna M. Guiu, Francisca Haro, Mireia Hernández, Estrella Lavado, Montserrat Llorens, Trinidad López, Montserrat Nieto, Mercè Oliva, Silvia Otin, Alexandra Plana, Noelia Reñé, Carme Rialp, Berta Rodoreda, M. Josep Rodriguez, Jordi Ros, Olivia Rubio, Dolors Saavedra, Anna M. Sagarra, Jaume Sanahuja, Consol Sánchez, Encarna Sánchez, Carme Sebastià, Fina Serra, Victoria Tarin, Joan Tobias, Judith Valecillos, Carles Valero, Ester Vila Baño, Ester Vila Marzà and Olga Villarta. We would also like to thank Montserrat Rodriguez and Pilar Puig (Althaia's Primary Health Centers) for her collaboration drawing up the brief intervention, Olga Llamazares Robles for her work and contributions to the study, and Lucia Ramos and Cristina de Vega for their logistical support.

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