How long will the immunity conferred by the COVID-19 vaccine last? Will the immune response be strong in all persons who receive it? These are frequently asked questions, as vaccines are set to roll out in India. The answers provided, be they six months or two years, assume that the strength and duration of the vaccine response are entirely dependent on the vaccine, without taking into account the age, nutritional status or pre-existing health conditions in the person receiving the vaccine.
Ignoring nutrition as an important influencer of both natural or innate immunity and acquired or adaptive immunity developed in response to infection or a vaccine, has consequences. It does not usually influence the decision to immunise but ignoring this aspect leads to neglect of nutrition in both public health policy and clinical practice.
A vaccine only provides the antigenic stimulus for the body to react. How capably the body reacts is considerably influenced by the nutritional status and will vary among individuals. Different facets of nutrition influence this response. The diet may be deficient in vital nutrients needed for a robust immune response. It may have elements that stoke high levels of inflammation in the body, consuming the building blocks of immunity which could be better utilised for the adaptive response to the vaccine. These effects are very likely if the diet has a high content of ultra-processed foods. The diet may also adversely affect the composition of our gut microbiome which, with its trillions of bacteria, is turning out to be an important influencer of our immunity. The healthy microbiome thrives on plant sourced soluble fibre in the diet and is destabilised by excessive sugar, trans fats, red and processed meats, alcohol and tobacco.
Studies on the immune response to several vaccines, ranging from polio and cholera to rotavirus, have revealed that deficiencies of several key nutrients adversely affect the strength of the immune response. Dietary protein deficiency is an obvious culprit, as antibodies are proteins too. Zinc and selenium are important minerals that have been shown to potentiate vaccine efficacy, apart from enhancing natural (innate) immunity. Vitamin E, too, has been proposed as a nutrient that enhances the immune response to a vaccine.
It is not just the antibody levels that are influenced by nutrition. The more durable component of the body’s immune response, cellular immunity, is affected by nutrition. In 2006, Japanese researchers reported that mice fed a diet with 5 per cent casein (milk protein) had lower T cell counts than mice fed 20 per cent milk protein. Production of interleukin-2, an important component of the chemical ammunition in the body’s response, was lower among the CD4+ T cells in the low protein diet group. The researchers concluded that “in addition to development of an effective DNA vaccine, the management of the nutritional state is important for the prevention of infectious disease by DNA vaccination.”
A double blind, placebo controlled clinical trial in France revealed that elderly persons living in a care home developed more antibodies and fewer respiratory infections, when compared to a similar group that did not receive these supplements. The immune system needs these two minerals for a strong response against viral infections. That is true for both natural immunity and for the immune response to an administered vaccine.
It is not necessary to supplement these nutrients along with the administration of the vaccine. That would not be possible in a mass immunisation programme, though nutrition counselling may be provided along with the vaccination during the post-injection observation period. What is needed is a reconsideration of policies that influence our agricultural priorities and shape our food systems. Enabling people to consume healthy diets will boost natural immunity that can fight off microbial infection and also to build a robust immune response when stimulated by a vaccine.
Are our agriculture and food systems presently configured to do that? Sadly not. We are presently offering cereals stripped of fibre and ultra-processed foods without adequate and affordable supply of pulses, millets, fruit, vegetables, nuts and fish which can provide us much needed proteins, vitamins, minerals and fibre. Even eggs are being removed from school mid-day meal menus in some states, despite their being power packed with the nutrients needed for immunity.
The impact of climate change also needs to be considered as we examine the future of food systems and nutrition in our country. A study from Columbia University (Data Science Institute, 2018) estimates the impact that climate change would have on India, by 2050. The nutrient quality of staples would decrease, according to the study. It projects that global warming would result in 49.6 million new zinc deficient persons, 38.2 million new protein deficient persons, apart from 106.1 million children and 396 million women who would be iron deficient. It concludes that diversifying crop production, replacing some part of rice cultivation with millets and sorghum, would make India’s food supply more nutritious, while reducing irrigation demand, energy use and greenhouse gas emission. “Such diversification of crops would also enhance India’s climate resilience without reducing calorie production or requiring more land”, the study concludes.
Even as we prepare to immunise our many millions, the big challenge of public health nutrition remains the production of easily available and affordable food sources which enable people to consume balanced diets which are physiologically suited to growth and good health across a long life course. These diets should also be predominantly plant-based, making them both nutritionally appropriate and ecologically sustainable. Ultra-processed foods should be regulated and taxed to decrease their production, promotion and consumption. These steps are not only good for human nutrition but also for reducing the risk of zoonotic infections by maintaining an ecological balance. The bonus is a benefit in slowing down climate change. Our protection does not lie only at the tip of a needle that injects the vaccine but even more so in the policies that determine what fills our plate when we eat.
This article first appeared in the print edition on January 16, 2021 under the title ‘Vaccine plus’. The writer, a cardiologist and epidemiologist, is President, Public Health Foundation of India (PHFI) and author of Make Health in India: Reaching a Billion Plus. Views are personal
