Positive thinking may boost vaccine response, study suggests

Scientists have found evidence that consciously cultivating positive thoughts after receiving a vaccine may strengthen the body’s immune response, according to new research. 

The study builds on earlier animal research suggesting that the brain’s reward system, which governs motivation and expectation, can influence immune function. Until now, however, it was unclear whether a similar brain–immunity link exists in people, The Independent writes. 

Researchers have long suspected that this mechanism may also help explain the placebo effect, in which a fake or inactive treatment produces real health benefits. A better understanding of this process could eventually lead to new strategies for improving vaccine effectiveness.

In the new study, scientists trained 85 healthy volunteers to deliberately increase activity in a key part of the brain’s reward network known as the ventral tegmental area (VTA). The participants’ brain activity was monitored using functional magnetic resonance imaging (fMRI), an advanced brain-scanning technique.

During the training sessions, participants used mental strategies — such as recalling positive memories like a past trip — while researchers measured activity in the VTA in real time. Participants received immediate feedback on how well their strategies worked, allowing them to adjust their thoughts to further increase VTA activity.

After the training, participants were given a hepatitis vaccine. Blood samples were collected before vaccination and for up to four weeks afterward to measure immune responses.

The researchers found that participants who were able to sustain higher levels of VTA activity showed a significantly larger increase in protective antibodies following vaccination. According to the study, the mental strategies used to maintain this heightened brain activity often involved positive expectations, suggesting a link to placebo-related processes.

“Sustained VTA upregulation was further linked to mental strategies involving positive expectations,” scientists wrote.

The findings point to a potential connection between specific brain circuits involved in motivation and expectation and the functioning of the immune system.

“It remains unknown whether a similar brain-immune link exists in humans and whether it involves conscious positive expectations,” scientists wrote in the study published in the journal Nature Medicine.

The researchers say the results could help identify biological targets related to the placebo effect in humans and inform future medical treatments.

“These findings suggest that consciously generated positive expectations can engage reward circuitry to influence immune function,” scientists wrote.

However, the researchers cautioned that further studies involving larger numbers of participants are needed. In this study, they measured only antibody levels, not whether the enhanced immune response translated into improved real-world protection from disease

By Sabina Mammadli