'Why Older People Are Harder To Vaccinate,' BBC News
By William Park, 14th October 2020. - Excerpts:
The strategy for rolling out a Covid-19 vaccine might be undermined by older people’s immune systems.
In a hypothetical alternative universe where we already have a vaccine against Covid-19, world leaders will have a choice about how to deliver it to the population. The most vulnerable people, along with the nurses, doctors and care workers who look after them, are likely to be protected first. If only it were that straightforward. The most vulnerable age group, the elderly, are particularly tricky to vaccinate. “We have very few vaccines designed for older populations,” says Shayan Sharif, a professor of vaccinology at the University of Guelph, Canada. “More often than not in the last century, most vaccines have targeted childhood diseases.”
Shingles is one exception, usually given to patients in their 70s, and there are one or two other vaccines for diseases like meningitis or human papillomavirus developed for young adults. But otherwise immunology is skewed in favour of children.
“We have a tremendous amount of knowledge about childhood diseases,” says Sharif. “When it comes to young adults, middle age and old age, we don’t have a lot of experience.”
To understand why older people are harder to vaccinate, we have to look at the differences in their immune system. Many infectious diseases are more severe in older adults than younger adults. Older people have more risk factors – a lifetime of exposure to carcinogens or other infectious diseases will increase the risk of future disease from new infections. But they also undergo something called immunosenescence – ageing of the immune system. Just like many other parts of the body, our immune system shows signs of our ageing. Some of the immune cells lose their function. The immune system is a very complex network of cell types that interact with each other. If something, somewhere within the system is not working, it interrupts the delicate balance of the immune response.
- How does the aging immune system work? When you are infected by a pathogen, the first layer of the immune system, the innate immune response, starts attacking the pathogen at the site of infection. For respiratory diseases, that could be the lungs, trachea or nose. White blood cells, or macrophages, attack the pathogen, swallowing it up before destroying it.
As those macrophages break apart the pathogen inside themselves, they present bits and pieces of it to another type of immune cell known as T cells. These serve as the “memory” of the immune system. T cells cannot see the pathogen by themselves and need certain macrophages, called antigen presenting cells, to show them the pathogen. That activates the next layer, the adaptive immune system. An effective vaccine may disrupt transmission, but it's unlikely one will completely stop transmission, experts say.
Vaccines have to compromise. While they might work well on one group of people, they might work less well on others. Currently there are a multitude of clinical trials for Covid-19 vaccines, many of which might make it all the way through development to approval. For Weinberger and Sharif, this is a good thing. Having a suite of vaccines that you can rely on means we can pick and choose the right one for the right scenario. One might work better for old people than others.
While all vaccines approved will need to show they protect against disease, not all vaccines will prevent transmission. No vaccine is going to be perfect. “There is not one vaccine that can provide 100% efficacy, not one, nada,” says Sharif.
Sometimes we put on our blindfold and we say vaccines are the only saviour, but that is not the case,” says Sharif. “Vaccines can take 14 to 28 days and require multiple injections and exposures. Immunotherapeutics can work in minutes and hours.”
"The most immediate hope for older people suffering with Covid-19 might be when we find a drug that reduces hospital time from weeks to days, says Sharif, or even one that negates the need for intensive care at all.
Hundreds of drugs are currently being researched as potential treatments for Covid-19...
Read More, https://www.bbc.com/future/article/20201013-why-older-people-are-harder-to-vaccinate
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* 'The Exclusion of Older Persons From Vaccine and Treatment Trials for Coronavirus Disease 2019—Missing the Target,' JAMA Network, Sept. 28, 2020. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2771091
"Older adults are at greatest risk of severe disease and death due to coronavirus disease 2019 (COVID-19). Globally, persons older than 65 years comprise 9% of the population,1 yet account for 30% to 40% of cases and more than 80% of deaths.
Unfortunately, there is a long history of exclusion of older adults from clinical trials. In response, the National Institutes of Health instituted the Inclusion Across the Lifespan policy, requiring the inclusion of older adults in clinical trials.3 Thus, we reviewed all COVID-19 treatment and vaccine trials on http://www.clinicaltrials.gov to evaluate their risk for exclusion of older adults (?65 years)"...
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