New research has found that most of the initial hesitancy towards COVID-19 vaccines was rooted in concerns that can be addressed and reduced over time.
In a study of more than one million people from Imperial College London's landmark REACT study, Imperial researchers found that almost two-thirds (65%) of people who were initially hesitant about getting a COVID-19 vaccine went on to get vaccinated at least once.
The findings, published today in The Lancet, show the most common reasons for hesitancy during the pandemic were concerns around the effectiveness of the COVID-19 vaccines and possible side effects. People who cited these reasons were more likely to change their minds and get vaccinated.
However, people who reported being hesitant because of a general anti-vaccine sentiment, a mistrust of vaccine developers, or who perceived their risk from COVID-19 to be low, remained more reluctant to receive a COVID-19 vaccine.
The findings shed new light on the main types of vaccine hesitancy in the UK during the COVID-19 pandemic and provide information about potential barriers to future vaccination uptake. The authors say that public health officials and policymakers need to recognise that certain types of hesitancy may be readily addressed, while others are more resistant to change.
Professor Paul Elliott, from Imperial's School of Public Health, co-senior author of the paper and director of the REACT community surveillance study, said: "What we learned from the COVID-19 experience is the importance of ensuring that people have access to reliable and trusted information so they can make well-informed decisions about their personal health choices. Reliable, easy-to-understand information, for example, on vaccine effectiveness and potential risks, is of particular importance in the case of a public health emergency such as COVID-19, which involved the rapid deployment at-scale of new vaccine technologies."
COVID-19 vaccine rollout
In the study, researchers from Imperial's School of Public Health analysed longitudinal survey data from 1.1 million adults from the Real-time Assessment of Community Transmission (REACT) Study – focusing on the initial COVID-19 vaccine roll-out between January 2021 and March 2022. They compared people's responses at enrolment to the REACT study with subsequent vaccination uptake from National Health Service vaccination records up to May 2024, to identify types of vaccine hesitancy and their drivers.
During the pandemic, participants were asked whether they had been vaccinated or intended to get vaccinated. Those who refused the vaccine, or were sceptical about vaccination, were asked about their reasons from a checklist of 23 options as well as a free text option.
The analysis found that overall, 3.3% of participants (37,982) reported some degree of COVID-19 vaccine hesitancy and subsequent vaccination data was available through NHS records linkage for 24,229 (64%) of them. Hesitancy rates generally declined over time from an initial high of 8% of those surveyed in January 2021, to a low of 1.1% at the start of 2022. There was a small increase in hesitancy to over 2.2% in February and March 2022, during the Omicron wave of the pandemic.
The researchers identified eight categories of vaccine hesitancy including concerns about effectiveness and side-effects, perception of low risk from COVID-19, mistrust of vaccine developers, and fear of vaccines and reactions. Among the 30,701 people who provided a reason for hesitancy, 41% (12,498) reported concerns around long-term health effects, 39% (11,953) wanted to wait to see whether the vaccine worked, and 37% (11,287) had concerns about side effects.
Reasons for hesitancy varied across demographic groups. For example, men were more likely than women to report not feeling COVID-19 was a personal risk (18% vs 10%); women more likely to be worried about fertility-related consequences (21% vs 8%); people aged 74 years or older were more likely to be against vaccines in general compared with 18–24-year-olds (12% vs 2.5%).
The analysis of subsequent vaccination behaviour found that the likelihood of remaining unvaccinated was higher for older people, women, people of Black ethnicity, people who were unemployed or living in deprivation, those with a history of COVID-19, and people with a lower level of education.
Professor Marc Chadeau-Hyam, from Imperial's School of Public Health and co-senior author of the paper, said: "The COVID-19 pandemic provided a unique opportunity to look at attitudes towards vaccination during a health emergency. At the time there was a lot of uncertainty among the public as we were dealing with a new disease and a relatively new vaccine platform. In our study we wanted to look at vaccine hesitancy in more depth to identify groups with more persistent forms of hesitancy and their main concerns. Understanding these drivers is critical to address vaccine uptake and better control disease spreads."
Professor Helen Ward, from Imperial's School of Public Health and the NIHR Imperial Biomedical Research Centre, said: "We show that certain types of vaccine hesitancy are more readily addressed than others, for example concerns relating to pregnancy or breastfeeding. Our study suggests that as the vaccine was rolled out, public confidence increased and the original vaccine scepticism was largely overcome."
The researchers explain that while the findings focus specially on the rollout of the COVID-19 vaccines – which were a relatively new vaccine platform at the time – the findings may provide important insights into wider phenomenon of vaccine hesitancy, including vaccination against childhood diseases.
Dr Helen Skirrow, a clinical lecturer from Imperial's School of Public Health specialising in maternal and childhood vaccine uptake, who was not involved in the study, explained: "We know that the impacts of declining childhood vaccine uptake are very real: in recent years we have seen a resurgence in cases of vaccine preventable diseases such as measles and in 2024 sadly the death of a child from measles in England. We need to ensure parents and families are getting clear and accurate information from health professionals so any concerns can be addressed. The evidence suggests most parents want to vaccinate their children but some might have questions that can easily be addressed through conversations with health professionals. It's important that children get their recommended doses of vaccines in order protect themselves, as well as their friends and families."
The legacy of REACT
The REACT programme was launched in April 2020 and quickly became one of the world's largest and most comprehensive coronavirus monitoring studies. Led by a team of researchers at Imperial College London in partnership with Ipsos MORI and commissioned by the Department of Health and Social Care, the two REACT studies provided invaluable information during the COVID-19 pandemic, giving insights into how many people were sick and the spread of immunity in the population.
Following the pandemic, the programme continues to be a valuable resource for scientific research. In 2025, REACT joined a leading national dementia programme to help boost recruitment for clinical trials. The first participants from the REACT cohort are expected to be recruited to the dementia programme in early 2026.
Professor Elliott added: "The REACT studies provided invaluable information during the COVID-19 pandemic, but they also leave an important research legacy beyond COVID-19. With the help of over three million participants who have signed up to our studies, we are looking at the long-term consequences of the pandemic as well as a focus on specific conditions such as dementia and bipolar disorder. This could one day translate into better treatments and earlier detection for these diseases."
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'Profiling vaccine attitudes and subsequent uptake in 1.1 million people in England: a nationwide cohort study' by Matthew Whitaker, Joshua Elliott, Ines Gerard-Ursin, et al. is published in The Lancet. DOI: XXX
