The review (pre-print) emphasises the importance of a healthy diet, particularly a plant-based one with high antioxidant and high-fibre content, as a consideration in bolstering the immune response to a vaccine.
“When we think of vaccine efficacy, we often think of the vaccine itself,” explains Annelise Madison, first author of the paper and a graduate student in clinical psychology at Ohio State University.
“My motivation was to draw attention to the fact that we bring important factors to the table as well - and those factors are modifiable.
"If we can address them now, when most of the world has yet to receive the vaccine, we have the chance to make our response to the vaccine quicker, more robust and lasting."
Along with diet, the team also discusses the effects stress, depression and poor health behaviours can have in diminishing the body's response to vaccination, and how that response can be enhanced.
Developing antibodies
"These findings suggest that with the COVID-19 vaccine, when people are more stressed and more anxious, it may take a little longer to develop antibodies, so they should probably allow a little more time before they assume they're protected," says senior author Janice Kiecolt-Glaser.
"Another possibility is that stress may erode protection more rapidly," adds Kiecolt-Glaser, a director of Ohio State's Institute for Behavioral Medicine Research and a professor of psychiatry and psychology at the University’s College of Medicine.
Out of these factors though, nutrition appears to be the least studied particularly dietary components and nutritional status in relation to vaccine responses among healthy adults.
The bulk of existing research focuses on populations in which undernourishment is common: children in developing countries and older adults.
Malnourished children are generally able to mount a sufficiently protective immune response upon vaccination, but the extent and duration may be less than ideal.
Across several studies, deficiencies in protein, vitamins A and D, iron, and zinc had little to no effect on vaccine response in children.
Vitamin D in particular has recently come under the microscope after an open letter was sent to world governments in December 2020, citing clear scientific evidence that vitamin D reduced Covid-19 infections, hospitalisations, and deaths.
The letter, signed by a wealth of health, science and medical experts from the UK, US, and Europe, called for immediate, widespread, increased vitamin D intake to 4,000 International Units (IU) per day (or at least 2,000) for healthy adults.
However, the review takes a more cautious approach, suggesting a single nutrient or nutrient deficiency may have little impact on vaccine response, and that an overall diet may be an important consideration.
The gut microbiome
The review also introduces another powerful factor, the gut microbiome as highly diet-dependent and influential in determining vaccine response.
As a primary example, dietary fibre intake promotes a greater abundance of bacteria like Bifidobacteria that produce short-chain fatty acids, which can boost antibody responses.
Along with exercise, the team also suggests boosting nutritional status via supplementation may result in a better antibody response to vaccines, especially in older adults, who often struggle to meet recommended daily nutritional guidelines especially if they live alone.
In one trial, elderly individuals who received a complete liquid nutritional supplement containing vitamins and minerals, including antioxidants, had higher antibody levels one month after influenza virus vaccine administration, compared to those who received the placebo.
However, a cited study thinks there is little evidence that micronutrient supplementation at the time of vaccination improves responses.
Even so, another trial among nursing home elderly revealed zinc supplementation successfully increased serum zinc levels and led to increased T cell multiplication which could bode well for vaccine responsiveness.
The review also cites preclinical evidence suggesting vitamin A supplementation may have a similar effect.
“Taken together, there is promising evidence that even short duration psychological and behavioural interventions can modify the immune system’s vaccine response as well as vaccine-related side effects,” the review states.
“Further research is needed to assess (1) the optimal dose and timing of the intervention, and (2) whether change in the targeted psychological construct or behaviour is the mechanism driving the improved vaccine response.”
“I know it can be difficult day in and day out during the pandemic to keep prioritising things we know we should do," adds Kiecolt-Glaser.
"But we could use this time as a wake-up call. These are important health behaviours to keep engaging in, especially as we're preparing to get vaccinated -- which is a really good thing."
Source: Perspectives on Psychological Science
Published online: DOI: 10.31124/advance.13528418.v1 (Pre-print)
“Psychological and Behavioral Predictors of Vaccine Efficacy: Considerations for COVID-19.”
Authors: Annelise Madison et al