A new study suggests that COVID-19 vaccine hesitancy may be linked to traumatic events experienced in childhood, such as neglect, domestic violence or substance abuse in the family home.

The observational study, conducted by researchers out of the U.K., found that reluctance or refusal to get COVID-19 shots was three times higher among those who had experienced four or more types of trauma as a child than among those who hadn't experienced any.

"Adverse childhood experiences (ACEs) can affect life-course health and well-being, including risk-taking behaviour and trust," the study's authors wrote.

Researchers found that increasing ACEs were also related to low trust in COVID-19 information, feeling "unfairly restricted" by government measures, as well as being in favour of ending mandatory face masks and removing physical distance requirements.

The findings were published Tuesday in the peer-reviewed .The study was conducted via a "nationally representative" telephone survey of adults living in Wales between December 2020 and March 2021. Out of an initial 6,763 people contacted, 2,285 met the eligibility criteria and were included in the final analysis.

According to the study, researchers asked participants about nine types of childhood trauma and whether they experienced any of them.

These types of trauma included physical, verbal, and sexual abuse; parental separation; exposure to domestic violence; and living with a household member with mental illness, alcohol and/or drug misuse, or who was in prison.

Researchers say they also collected personal details and experiences of long-term health conditions, levels of trust in COVID-19 information from governments, and attitudes towards public health restrictions and vaccination.

According to the study, approximately half of respondents (52 per cent) said that they hadn鈥檛 experienced any childhood trauma, while one in five reported they had experienced at least one type.

Researchers found about one in six people surveyed (17 per cent) reported experiencing two to three trauma types, and one in 10 (10 per cent) reported four or more.

IMPACT OF CHILDHOOD TRAUMA

According to the study, vaccine hesitancy was three times higher among those with a childhood trauma count of four or more, and was more often reported in younger age groups.

Researchers estimate that the likely rates of vaccine hesitancy according to childhood trauma and age range from roughly 3.5 per cent among those aged 70 and older with no experience of childhood adversity, to 38 per cent among those between the ages of 18 and 29 who had experienced four or more types of trauma.

Support for getting rid of mandatory face coverings was four times as high among those who had experienced four or more types of childhood trauma, compared to those who hadn't experienced any.

Younger males with no history of long-term medical conditions were "significantly associated with this stance" on masking, researchers said.

The study found that experiencing four or more types of trauma as a child was also associated with a desire to end physical distancing requirements.

"The likelihood of admitting to flouting COVID-19 restrictions occasionally rose in tandem with the childhood trauma count," researchers noted in the study.

According to the findings, going against public health restrictions was twice as high for those who had experienced four or more types of trauma than among those who hadn't experienced any (38 per cent versus 21 per cent), after taking into account sociodemographic factors, previous COVID-19 infection and health history.

However, since the study was observational in its method, researchers acknowledge there are "several caveats" to the findings, most notable that the study could not establish cause.

Although in line with other telephone surveys, researchers say the response rate was only around 36 per cent, and the findings relied on personal recall. In addition, women were overrepresented in the study, while the numbers of people from ethnic minority backgrounds were underrepresented. Researchers say future research should work to address these inequities in representation.

Despite such caveats, researchers noted that those who have experienced childhood trauma are "known to have greater health risks across the life-course. Results here suggest such individuals may have more difficulty with compliance with public health control measures and consequently require additional support."

Researchers say this is not only important during the COVID-19 pandemic, but for other public health emergencies that may arise in the future. They say the findings suggest that experts and public health officials need to "urgently" find ways to increase trust and compliance with health guidance for those with childhood trauma.

If not, researchers say those in this group remain at higher risk of infection and pose a potential transmission risk to others.

"Increasing the appeal of public health information and interventions, such as vaccination, to those who have experienced ACEs should be considered in health protection responses," the study's authors wrote.

"Longer term, however, achieving better compliance with pandemic and other public health advice is another reason to invest in safe and secure childhoods for all children."