With any luck, at least one of the vaccines being developed will protect us from Covid-19. However, when candidate vaccines are tested in large groups of people, not everyone will respond in the same way. We may find that one type works better in young adults and another works for elderly people. This will open up a new frontier of science concerning vaccines tailored to benefit different groups of people. In 2021 we will understand that one-size-fits-all is not optimal for anyone.
There are still many gaps in our understanding of how vaccination works. We know which immune cells have to be activated – memory B cells and T cells – and we have ways of testing whether they have been. But we don’t understand what’s needed to ensure that immunity lasts for many years, rather than for a few weeks or months. We also know that elderly people tend not to respond to vaccines as well as younger people, but we are not sure why. It’s not that our immune system simply becomes unresponsive as we age – elderly people are also more likely to suffer from auto-immune diseases, caused by unwanted immune responses. Rather, our immune system somehow goes awry in old age.
Understanding why this occurs will open up the possibilities of vaccines that are especially effective in older people, specifically targeting a part of the human immune system known to work well in old age. There is already a precedent for this. A molecule called flagellin, found in bacteria, has been identified as one of the few germ molecules easily detected by the immune system in senior citizens. Including this molecule in a flu vaccine has been shown to help stimulate an appropriate immune response in elderly people.
And that will just be the beginning. Every person’s immune system is configured slightly differently. In part, this is down to our genes – those which vary the most from one person to the other are not to do with anything physically obvious, such as our eye, skin or hair colour; they are immune-system genes. This is one reason why people fare differently when exposed to the same infection. And the infections each of us has been exposed to, our gender, where we were brought up, our diet and levels of exercise also all have an affect.
In 2021, we will increase our knowledge of the diversity of human immune responses. One large collaboration led by the US National Institute of Allergy and Infectious Diseases has already begun collecting huge amounts of information about different people’s immune responses during Covid-19 infection. We will also see the results from several phase-3 clinical trials of Covid-19 vaccine candidates and, in most cases, this will include careful profiling of people’s immune responses. This will seed new insights on immunity and generate the data needed for vaccines to be used in a more personalised way.
We will also understand more deeply other issues that affect our response to vaccines. It may emerge, for example, that giving someone a vaccine at a certain time of day will enhance its efficacy, as we know that our immune reactivity fluctuates by day and night.
Not only will these details help us tackle the current coronavirus pandemic, they will change how we use vaccines in general. In 2021, we will see an important step being taken towards truly personalised vaccines that work.
Daniel M Davis is an immunologist and author of The Beautiful Cure