Article Text

Original research
Changes in primary care visits arising from the COVID-19 pandemic: an international comparative study by the International Consortium of Primary Care Big Data Researchers (INTRePID)
    1. 1 Department of Family and Community Medicine, University of Toronto, Toronto, Ontario, Canada
    2. 2 Departments of Research and Innovation and Family Medicine-North York General Hospital, Toronto Western Family Health Team-University Health Network, Toronto, Ontario, Canada
    3. 3 Department of Public Health and Caring Sciences, Uppsala Universitet, Uppsala, Sweden
    4. 4 Department of Statistical Sciences, University of Toronto, Toronto, Ontario, Canada
    5. 5 Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK
    6. 6 Norwegian Institute of Public Health, Oslo, Norway
    7. 7 Department of General Practice, University of Oslo, Oslo, Norway
    8. 8 Division of Family Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
    9. 9 Department of General Practice, The University of Melbourne, Melbourne, Victoria, Australia
    10. 10 International Healthcare Center, Asan Medical Center, Seoul, South Korea
    11. 11 Department of Family Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
    12. 12 Department of Family Medicine and Primary Care, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China
    13. 13 Department of Family Medicine and Primary Care, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
    14. 14 DARTNet Institute, Aurora, Colorado, USA
    15. 15 Research Unit for General Practice, NORCE Norwegian Research Centre AS, Bergen, Norway
    1. Correspondence to Dr Karen Tu; k.tu{at}


    Introduction Through the INTernational ConsoRtium of Primary Care BIg Data Researchers (INTRePID), we compared the pandemic impact on the volume of primary care visits and uptake of virtual care in Australia, Canada, China, Norway, Singapore, South Korea, Sweden, the UK and the USA.

    Methods Visit definitions were agreed on centrally, implemented locally across the various settings in INTRePID countries, and weekly visit counts were shared centrally for analysis. We evaluated the weekly rate of primary care physician visits during 2019 and 2020. Rate ratios (RRs) of total weekly visit volume and the proportion of weekly visits that were virtual in the pandemic period in 2020 compared with the same prepandemic period in 2019 were calculated.

    Results In 2019 and 2020, there were 80 889 386 primary care physician visits across INTRePID. During the pandemic, average weekly visit volume dropped in China, Singapore, South Korea, and the USA but was stable overall in Australia (RR 0.98 (95% CI 0.92 to 1.05, p=0.59)), Canada (RR 0.96 (95% CI 0.89 to 1.03, p=0.24)), Norway (RR 1.01 (95% CI 0.88 to 1.17, p=0.85)), Sweden (RR 0.91 (95% CI 0.79 to 1.06, p=0.22)) and the UK (RR 0.86 (95% CI 0.72 to 1.03, p=0.11)). In countries that had negligible virtual care prepandemic, the proportion of visits that were virtual were highest in Canada (77.0%) and Australia (41.8%). In Norway (RR 8.23 (95% CI 5.30 to 12.78, p<0.001), the UK (RR 2.36 (95% CI 2.24 to 2.50, p<0.001)) and Sweden (RR 1.33 (95% CI 1.17 to 1.50, p<0.001)) where virtual visits existed prepandemic, it increased significantly during the pandemic.

    Conclusions The drop in primary care in-person visits during the pandemic was a global phenomenon across INTRePID countries. In several countries, primary care shifted to virtual visits mitigating the drop in in-person visits.

    • COVID-19

    Data availability statement

    Data are available upon reasonable request. All data are subject to local regulations for data sharing that vary from country to country. In all settings, individual-level data are not publicly available. We will provide aggregated visit data by country for review if requested. Analytic code for analysis of the data is also available on request.

    This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

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    Strengths and limitations of this study

    • The multiple countries involved to be able to compare experiences in the primary care setting and the large volume of patients visiting primary care around the world is a strength of this study.

    • Coming together to form the INTernational ConsoRtium of Primary Care BIg Data Researchers (INTRePID) with local primary care physicians and data experts having the ability to provide local context for the interpretation of findings is a strength of this study.

    • The heterogeneity of available data ranging from national level data to only one or a few clinic’s data in one country may have limited the representativeness of individual countries data.

    • The capture of virtual visits and contacts of primary care physicians and their patients may be more incomplete in settings that did not have remuneration for virtual visits.


    On 11 March 2020, the WHO declared the spread of COVID-19 a pandemic.1 Almost 2 years later, with over 425 million cases and nearly 6 million deaths worldwide as of 24 February 2022,2 new variants spreading and vaccination issues, the end to the pandemic is uncertain. The COVID-19 pandemic has presented unprecedented challenges in all aspects of daily life around the world, especially in healthcare delivery including primary care.3 4 Primary care is the foundation on which the highest functioning healthcare systems are built.5 Primary care practice and policy has the potential to affect the health impacts of the pandemic, with respect to screening, diagnosis, treatment and prevention of patients with COVID-196 and through non-COVID-19 disease management and prevention. Although recent studies have shown less respiratory illnesses as a result of COVID-19 prevention strategies7 8 and lower overall death rates in Norway,9 likely due to less spread of other infectious diseases,10 the unintended consequences of the pandemic are coming more and more to light. Estimates of excess deaths due to the COVID-19 pandemic suggest that the health consequences of the pandemic are not limited to those infected with COVID-19, with more people dying from non-COVID-19 causes11–13 and many negative indirect effects as well.14 15

    Although all countries have their own unique primary care healthcare system, changes in healthcare delivery in response to the pandemic, variable degrees of COVID-19 spread2 and government and public health-imposed containment measures,16 comparisons between countries may help contextualise local measures. Almost a decade ago, responding to ‘emerging infectious diseases with potential widespread health and economic impact’ was identified as an international primary care research responsibility.17

    In response to the need for primary care to prioritise acute care and prevent the spread of disease, healthcare funders in many countries expanded or introduced virtual care (telephone or video) as a mode of delivery for physician visits.18 19 Yet the design and duration of these virtual care programmes has varied across jurisdictions. There is a lack of evidence comparing the experiences with virtual care in different settings that could be used to support ongoing changes in primary care beyond the pandemic.20 21 We set out to compare the pandemic impact on volume of primary care visits, as well as uptake of virtual care, in primary care settings in nine different countries around the world.


    Triggered by the onset of the COVID-19 pandemic and the understanding of common challenges worldwide, primary care researchers in nine different countries joined together to form the INTernational ConsoRtium of Primary Care BIg Data Researchers (INTRePID). INTRePID countries include Australia, Canada, China, Norway, Singapore, South Korea, Sweden, the UK and the USA.

    We conducted an international comparative study of changes in primary care visit volumes and the switch to virtual care in INTRePID countries in 2019–2020 to capture the effects of the onset of the global COVID-19 pandemic. Electronic medical record data or physician billing claims data covering the primary care population in a given region, or a sample of the population, were used to estimate weekly visit volume and format of care delivery (see online supplemental material for description of country specific data sources). There were no restrictions based on age or sex in any of the data and all patients presenting to the primary care clinics with a visit to the primary care physician (PCP) in the various settings in INTRePID countries were included. Data were extracted and analysed in each individual country, and aggregated results were shared centrally for comparative analysis. We considered key features of each country’s primary care healthcare system, COVID-19 incidence patterns2 and containment and health indices16 (a composite measure of 11 policy response indicators such as school and workplace closures, travel bans, testing policy and contact tracing) in the interpretation of our findings.

    Supplemental material

    All INTRePID countries had some level of public funding for primary care delivery and varied based on the extent of funding via private insurance. In all INTRePID countries except for the USA and Singapore, primary care delivery is primarily publicly funded. Apart from Canada, Sweden and the UK, PCPs in INTRePID countries are paid primarily by fee for service. PCPs include family doctors, family physicians, general practitioners or GPs, list patient doctors, polyclinic doctors and in the USA also includes general internists and paediatricians. Healthcare systems varied based on the degree to which patients were expected to cover or have insurance to cover payments and copayments for visits and medications. In all countries except China, South Korea and most situations in the USA, PCPs act as gatekeepers for access to care from secondary care (table 1a). In all INTRePID countries, PCPs provide a broad scope of practice including preventive, acute and chronic disease diagnosis, and management.

    Table 1

    (A) Summary of primary care healthcare systems in INTRePID countries. (B) Pandemic timing, virtual care policies and data available for INTRePID countries

    Most INTRePID countries responded to the WHO pandemic declaration with corresponding declarations of a ‘state of emergency’ and implemented healthcare policies and restrictions to prevent the spread of COVID-19 (table 1b). In Australia, Canada, Norway, Sweden and the UK, PCPs were encouraged to limit in-person contacts and use virtual care as much as possible, whereas in China, South Korea and Singapore support for virtual care was more limited, with variation in the extent of remuneration and the duration of time it was available. At the University of Hong Kong-Shenzhen Hospital in China, virtual care in primary care was only available shortly after the pandemic started in China from February 2020 to April 2020. Virtual care became permitted in South Korea from the end of February 2020. In Singapore, telephone and video visits were not offered as services billed by PCPs at any point before or during the pandemic. Administrative and support staff within these clinics were more likely to follow-up with patients by telephone during the pandemic, but these contacts were not captured as part of our estimates of visit volume. In all other countries virtual care was a reimbursable primary care visit delivery mode until the end of 2020 and policies for extensions have occurred such that it is still going on today in many countries (table 1b).


    Primary outcome measures were the total number of primary care visits per week in each country and the total visits per week that were virtual. Visits refer to a patient and PCP interaction that is remunerated by local publicly or privately funded health insurance plans. The term visit can be referred to as an attendance, encounter, consultation, contact or event in various INTRePID countries. We considered the format of care delivery. Using methods appropriate to data sources in each country, primary care visits were classified as in-person or virtual. Virtual visits included both telephone and video consultations between patients and GPs as it was not possible to distinguish between these types of visits in all countries. As email correspondence between patients and PCPs were unable to be identified in all INTRePID countries, we elected to only include telephone and video visits except in Norway where e-consultation (secure e-mail correspondence) was the main form of virtual care both prepandemic and in the pandemic period. Separate counts for each week in 2019 and 2020 were created for in-person visits and for virtual visits, which added together created the total visit volume for each week. To facilitate comparison between countries, weekly visit volume was calculated by the International Organization for Standardization (ISO) ( week.

    Data analysis

    We summarised weekly in-person, virtual and total visit volume across all weeks in 2019 and 2020 in the INTRePID countries. The total visit volume and proportion of virtual visits were obtained during the pandemic period in 2020 as well as the corresponding period in 2019 (the prepandemic period). The start of the pandemic period coincided with the global pandemic declaration by the WHO on 11 March 2020 until the end of 2020 (pandemic period: ISO weeks 12–52) for all countries except China where the local pandemic was declared on 23 January 2020 (pandemic period: ISO weeks 5–52).

    To examine the impact of the pandemic on total visit volume in each country, we estimated rate ratios (RRs) comparing the mean weekly visit volume in the pandemic period and prepandemic periods. In countries where virtual care was offered before and after the pandemic (Norway, Sweden and the UK), we repeated the same analysis for weekly virtual visit volume to evaluate the relative change in mean weekly virtual visit rate in the pandemic period compared with the prepandemic period. For both analyses, RRs were obtained from a Poisson generalised linear model with an indicator of the pandemic period included as a covariate. We obtained robust SEs, two-sided p values and 95% confidence intervals (CIs) using the Newey-West method to account for autocorrelation. Bandwidth selection was performed using the procedure of Newey and West 1994 with prewhitening. All analyses were conducted with R V.4.0.3.

    Role of the funding source

    None of the study funding sources played a role in the study design, collection, analysis, interpretation of the data, writing of the report or in the decision to submit the paper for publication.

    Patient and public involvement

    Neither patients nor the public were directly involved in the conduct of the study.


    Overall, we captured 80 889 386 primary care visits in INTRePID countries in 2019 and 2020 (table 2). At the onset of the pandemic, visit volume decreased in all INTRePID settings, with variation across countries in the timing and duration of this change and the degree to which virtual visits increased to fill the gap in in-person visit volume (figure 1). Comparing the average weekly visit volume in the pandemic period to the prepandemic period, we observed significant decreases in China, Singapore, South Korea, the USA, but not in Australia, Canada, Norway, Sweden or the UK (table 3).

    Figure 1

    Changes in primary care visits, COVID-19 spread and health containment indices in INTRePID countries in 2019–2020. INTRePID, INTernational ConsoRtium of Primary Care BIg Data Researchers.

    Table 2

    Total number of visits (in-person and virtual) in 2019–2020 and the total visit volume and proportion of virtual visits in the prepandemic and pandemic periods for the INTRePID countries

    Table 3

    Relative change in the average weekly visit volume comparing the pandemic period to the prepandemic period

    All INTRePID countries experienced a drop in in-person visits to PCPs immediately following the pandemic onset and showed various degrees of recovery either through a rebounding of in-person visits or a switch to virtual visits (figure 2). The countries with the largest decreases in visit volume during the pandemic (China (RR 0.72 (95% CI 0.58 to 0.88)), Singapore (RR 0.73 (95% CI 0.65 to 0.83)), South Korea (RR 0.86 (95% CI 0.79 to 0.94)) were those who did not shift to virtual care (table 2, figure 2). In countries that supported virtual care during the pandemic period, the decline in in-person visits appeared to be partially or completely mitigated by an increase in virtual visit rate. In Canada, Australia and the USA, virtual visits were not offered before the pandemic due to the regulatory environment or accounted for <1% of prepandemic visit volume. However, the overall visit volume in Canada was relatively stable across the pandemic and control periods, with a large increase in virtual care (77.0% of the weekly visit rate in the pandemic period). A similar pattern was observed for the uptake of virtual care in Australia (41.8%) and the USA (27.5%) (table 2, figure 2). Sweden and the UK were the only countries in which telephone or video visits were widely used prepandemic, while a small proportion of visits occurred virtually in the prepandemic period in Norway. During the pandemic, virtual visits increased substantially in all three of these countries (table 3).

    Figure 2

    Year-over-year change in weekly visit volume, by country and visit type.


    Principal findings

    The drop in in-person visits in primary care with the onset of the pandemic was a global phenomenon across INTRePID countries. Countries that embraced virtual care were able to mitigate the drop in in-person visits such that overall visit volume to primary care was largely maintained. The countries that had the lowest uptake of virtual care had the lowest rates of total visit volume during the pandemic compared with the prepandemic period. The impacts of replacing in-person visits with virtual ones to maintain stable primary care service levels remains to be seen and is an area for future research. The experiences across INTRePID countries illustrate that there is considerable variability in how much virtual care was used during the pandemic and to what degree prepandemic service patterns have returned.

    The uptake of virtual care did not appear to be related to the degree of COVID-19 spread (figure 1) as the countries with the greatest COVID-19 incidence (Sweden, USA and UK) were similar in proportion of visits that were virtual during the pandemic as countries that had moderate or relatively lower COVID-19 incidence. Given that the health containment indices (figure 1) were similar among most INTRePID countries, it is difficult to correlate health containment indices with visit patterns. However, Norway did have slightly lower health containment index scores than other INTRePID countries and was the country that best maintained prepandemic visit volume in the pandemic period. It is interesting to note that the three countries that were the highest in rates of virtual care in the pandemic period (Canada, UK and Sweden) were the three countries among INTRePID that had primarily capitation payment model primary care systems. It is possible that a capitation payment model system whereby a physician has a set group of patients that they are remunerated to care for, regardless of the number of times a patient is seen, may be more amenable to virtual PCP visits.

    Funding policies may explain some of the differences in virtual care uptake during the pandemic. The low number of virtual visits observed in China, South Korea and Singapore reflect policy decisions on how PCPs were or were not renumerated for virtual care. However, there was also variation among the other INTRePID countries where policies supported renumeration for virtual visits such that funding policies alone may not fully explain the differences in primary care visits we observed. Other factors such as the perceived effectiveness of virtual visits, perceived barriers in patient access and satisfaction with virtual care may have influenced both the availability and uptake of virtual visits in primary care across INTRePID countries.

    The large immediate drop in in-person visits seen in Canada and China at the onset of the pandemic may reflect previous experience with severe acute respiratory syndrome (SARS-CoV-1),22 whereas other countries did not have as large a change in in-person visits. However, our results illustrate that China and Canada adopted different responses to adapt to this sudden change in in-person primary care services. In Canada, in-person visits were replaced with virtual visits such that total visit volume was largely maintained, and virtual visits continued to be the dominant format of care delivery throughout 2020. In China, the shift to replace missing in-person visits with virtual ones was minimal. As a result, total visit volume was lower during the pandemic than in the prepandemic period, but the number of in-person visits returned to prepandemic levels by the end of 2020. Although the health impacts of these differences remain to be seen, this example illustrates the value of comparing pandemic responses across jurisdictions. Studies done in a single country or health system might not recognise how the response taken locally during the pandemic compares with others internationally. The ability to compare experiences through INTRePID can provide further insight into the advantages and disadvantages of adopting virtual care models during the pandemic and beyond.

    Comparison with other studies

    Previous studies have looked at the switch to virtual care in one or a few jurisdictions.23–25 Reduced access to in-person health services at the start of the pandemic is a common finding and consistent with our results across INTRePID. Researchers have also observed that the content of primary care visits changed during the pandemic.26–28 This could be the result of changing population health needs or priorities during the pandemic or related to the increased use of virtual care. The current study illustrates that the increased use of virtual care was not universal and provides a foundation for future studies into the consequences of ongoing changes in primary care across INTRePID. This study allows for the individual countries to understand how they compare with other countries in the uptake of virtual visits in primary care. Experts in some jurisdictions predict that primary care may be changed forever or at least for the foreseeable future.29 30 This study is an illustration of the adaptability of primary care in the face of a pandemic around the world. There is a need for continued research to support ongoing changes in primary care beyond the pandemic and INTRePID is well positioned to meet this challenge.

    Strengths and limitations

    Over the course of the past 2 years, COVID-19 and the effects of the pandemic have dominated the medical literature. While international comparative studies on COVID-19 impact or response are not new in primary care, previous studies have been largely descriptive3 31 or based on survey responses.32 The formation of INTRePID, using local experts to discuss and agree on comparable measures, perform local analysis, provide local context for interpretation of findings, the large volume of patients visiting primary care around the world and the focus on primary care are strengths of this endeavour.

    There are nevertheless several limitations we must acknowledge with this study. First, there was a large variation of data availability in INTRePID countries. The availability of data ranged from national level data to only one or a few clinic’s data in one country. In countries where there were fewer physicians contributing, the data may be less representative of the whole country and the national COVID-19 spread, and health containment indices may not accurately reflect the situation in settings that were locally sampled. Second, while we defined visits as those that we could reasonably measure through billing data sources in each country, we acknowledge that this approach does not capture all the activities of PCPs and in countries that did not allow for remuneration of virtual care, the activity of PCPs may be differentially under captured here. Third, it is possible that other care providers increased delivery of primary care services in some jurisdictions, and we were not able to measure this in this study. Last, we were limited to only having weekly visit data in 2019 and 2020 and focused our analyses on the average change in weekly visit volume comparing the pre and post pandemic periods rather than analysing trends in visit volume or format of care. We also only present unadjusted analyses as demographics and other environmental factors were not available for analysis.


    The aftermath of the pandemic will only be known in the time to come. How the switch to virtual care may have impacted the quality of care provided is not yet known, will be subject for future study and will be of interest to both patients, providers and policy makers as the pandemic resolves.21 31

    We have established the foundation for future international comparative studies on the impact of the pandemic on primary care in multiple countries.33 Primary care around the world has proven to be flexible and adaptable to provide patient care throughout the pandemic.

    Data availability statement

    Data are available upon reasonable request. All data are subject to local regulations for data sharing that vary from country to country. In all settings, individual-level data are not publicly available. We will provide aggregated visit data by country for review if requested. Analytic code for analysis of the data is also available on request.

    Ethics statements

    Patient consent for publication

    Ethics approval

    This project received research ethics board (REB) approval from the University of Toronto (#40129) and North York General Hospital (#20–0044). Further REB approval was sought and attained by investigators in each country as necessary according to local regulations.


    Thank you to the patients and primary care providers in INTRePID countries who allow data sharing. Norway: Jonas Minet Kinge and Kjetil Elias Telle, Norwegian Institute of Public Health helped in providing and presenting the Norwegian data. UK: Julian Sherlock Data Analyst Oxford-Royal College of General Practitioners Clinical Informatics Digital Hub helped in providing and presenting the UK data. USA: Amanda Ratigan Director of Analytics, DARTNet Institute, helped in providing and presenting the US data. Canada: Angela Ortigoza Bonilla, helped in the revisions of the manuscript.


    Supplementary materials

    • Supplementary Data

      This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.


    • Twitter @Lusignan_S, @SFlottorp, @Cmhallinan, @jo_manski

    • Collaborators Simon de Lusignan; Signe Flottorp; Lay Hoon Goh; Jessica Gronsbell; Christine Hallinan; Uy Hoang; Seo Young Kang; Young Sik Kim; Robert Sarkadi Kristiansson; Zhou Li; Zheng Jye Ling; Jo-Anne Manski-Nankervis; Amy Pui Pui Ng; Wilson D Pace; Ellen Stephenson; Karen Tu; Knut-Arne Wensaas; William CW Wong.

    • Contributors This study was born out of a recognition that the onset of the pandemic changed the delivery of primary care globally. In Canada health services researchers KT and ES and biostatistician JG accessed UTOPIAN and conducted the central analysis on all countries and wrote the first draft of the manuscript. In Australia, biostatistician CMH and primary care researcher JAMN accessed Patron. In China, primary care researchers APPN, ZL and WCWW accessed the Family Medicine General Practice Clinic at the University of Hong Kong Shenzhen Hospital. In Norway, health services researcher SF and research fellow KAW accessed the Norwegian Health Economics Administration data. In Singapore, primary care researcher LHG and health informatics researcher ZJL accessed the National University Polyclinics data. In South Korea, primary care researchers SYK and YSK accessed the data in Family Medicine in the Asan Medical Center. In Sweden, PhD candidate RSK accessed the Region Uppsala data. In the UK, primary care researchers SdeL and UH accessed the Oxford-Royal College of General Practitioners (RCGP) database. In the USA, health services researcher WDP accessed DARTNet. All countries had clinical primary care expertise and experience and provided interpretation of their local data. All authors provided critically important revision of the manuscript, approved the final version and accept responsibility to submit for publication. KT is the guarantor and responsible for the overall content, had access to the data centrally, accepts full responsibility for the work and conduct of the study.

    • Funding This work was supported by the Canadian Institute of Health Research (CIHR) Operating Grant: COVID-19 Mental Health & Substance Use – Matching Access to Service with Needs: grant #450302, the North York General Hospital Exploration Fund and the Rathlyn Foundation.

    • Competing interests All authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare the following: KT receives a Research Scholar award from the Department of Family and Community University of Toronto and research salary support from North York General Hospital, Toronto Western Family Health Team and the Rathlyn Foundation and has received grant funding from the Canadian Institutes of Health Research (CIHR), The College of Family Physicians of Canada/Foundation for Advancing Family Medicine/CMA Foundation, Heart and Stroke Foundation of Canada, Heart and Stroke Foundation of Ontario, Department of Defense United States of America, University of Toronto-Department of Family and Community Medicine), MaRS Innovation Fund, Canadian Dermatology Foundation, CRA (CIORA), PSI Foundation, Cancer Care Ontario, St. Michael’s Hospital Foundation, Toronto Rehab Institute Chair Fund, UTOPIAN, Arthritis Society, MS Society of Canada, The Canadian Vascular Network and Ontario SPOR Support Unit Targeted IMPACT Award. RSK teaches at the Swedish advanced training programme in quality improvement and owns stocks in the Swedish healthcare company Ambea. JG has received grant funding from NSERC and consulting fees from Verily Life Sciences. SdeL is the director of the Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) as part of his academic post at Oxford. He has received payment to his research group for health services and primary care research from the University of Oxford and the University of Surrey and a wide range of grant funding through his university for vaccine related research from AstraZeneca, GSK, Sanofi, Segirus and Takeda. WDP has received grant funding from NIMCH, sits on the advisory board of AT Still Research Foundation, has stock in Moderna and Pfizer and received supplies from TEVA. ES receives a CIHR postdoctoral fellowship award. No other authors have any other conflicts of interest to declare. All funding sources were not involved in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and the decision to submit the article for publication. The researchers are all independent from funders, and all authors had full access to all the data in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.