The unexpected ways vaccines could boost your health
As US political leaders question vaccine safety, scientists point to studies that show the shots might provide benefits beyond their intended targets.
Despite being among the great scientific breakthroughs of all time, vaccines are under fire as top US government officials cast doubts on their safety.
But as doctors and vaccine deniers spar over the safety of vaccines, emerging evidence finds that some vaccines aren’t only good at preventing the disease or virus they target but also might have broader or even unrelated health benefits.
US Health Secretary Robert F Kennedy Jr has raised questions about numerous vaccines and taken steps to make it easier for parents to opt out of vaccinating their children. And in its strongest anti-vaccine move to date, a federal vaccine panel voted last Friday to scrap a recommendation that all newborns get the hepatitis B vaccine. While the focus has been on childhood vaccines, researchers are studying whether certain adult vaccines can be used for dementia prevention or for improving cancer survival rates.
The shingles vaccine, for example, might help reduce the risk of developing dementia later. The Covid-19 vaccine, when given to certain cancer patients, increased their survival rates, one recent study found.
An old tuberculosis vaccine – bacillus Calmette-Guérin, or BCG – is being studied to prevent Alzheimer’s disease. It has also been shown to decrease infant mortality in parts of the developing world where it is still widely used.
It is a concept known as trained immunity. Adaptive immunity trains the immune system to recognise a specific pathogen. Trained immunity is a form of innate immune memory whereby the body generates a more robust response to even unrelated exposures.
“Trained immunity is broad,” says David Topham, a professor of microbiology and immunology at the University of Rochester Medical Center. “Trained immunity is a biological phenomenon – cells that mediate trained immunity are changed by some immune event and they stay that way. They are experienced in some way.”
Shingles, also known as herpes zoster, is caused by the reactivation of the chickenpox virus, resulting in a painful rash. Two doses of the shingles vaccine are recommended for all healthy adults who are ages 50 and older.
Studies have found adults who receive the shingles vaccine have a lower risk of developing dementia later.
But many of the studies might have a bias and researchers say people who get vaccines in general could have healthier behaviours that might be contributing to that reduced risk, rather than the vaccine itself.
Two recent studies were able to compensate for that bias by comparing people close in age and behaviours.
An April study in Nature looked at seniors in Wales who were 79 years old after a shingles-vaccination program started. The researchers compared 79-year-olds who were just young enough to be eligible for the program with those who were just a few weeks older and ineligible because they were 80.
“We estimate that over a seven-year follow-up period, the shingles vaccine averts one in five new dementia diagnoses,” says Dr Pascal Geldsetzer, an assistant professor of medicine at Stanford University and senior author of the study.
The findings were replicated in a similar study in JAMA this year, looking at seniors in Australia when the government rolled out a similar shingles-vaccine program.
Because the chickenpox varicella-zoster virus remains dormant in the nervous system, it is plausible that it is a chronic stressor causing chronic inflammation, says Geldsetzer. “We know inflammation is a bad thing for many chronic diseases, including dementia,” he says. “Reducing these activations through shingles vaccination may well have benefits.”
The Wales and Australia studies looked at adults who got the Zostavax vaccine, which was discontinued in the US in 2020. Adults now get the Shingrix vaccine. Geldsetzer says that if the mechanism at work is chickenpox virus-specific, he expects the effect on dementia would be even larger with the newer vaccine but, if it is a broader immune mechanism, it might not have the same effect.
In other research, an October study in the journal Nature found that some cancer patients who received the Covid-19 vaccine while undergoing immunotherapy had a more than 50 per cent greater survival rate than those who didn’t. The patients had stage three or four lung cancer or melanoma.
Other vaccines, for flu or pneumonia, didn’t have the same benefit, said Dr Steven Hsesheng Lin, a professor of radiation oncology at MD Anderson Cancer Centre in Houston and senior author on the study.
Lin attributes the benefit to mRNA vaccines specifically. An mRNA vaccine uses messenger RNA to get your cells to make a piece of a virus that is harmless. This sets off an immune response to teach your body how to combat the disease without being exposed to its harms. Pfizer and Moderna’s Covid-19 vaccines were the first US federally approved mRNA vaccines.
“The cells gobble up the vaccine, and it’s the nucleic acid of the mRNA that sets off an alarm switch in the body as if the body is being invaded by viruses, but it’s not,” says Lin. This sets off a chain reaction where cytokines, or inflammatory mediators, wake the immune system — giving cancer patients getting immunotherapy an extra boost.
The immune response, however, eventually weakened so the Covid-19 vaccine had to be given within 100 days of the immunotherapy, said Lin.
The BCG vaccine given to newborns in many parts of the developing world to prevent tuberculosis also seems to have a systemic immune response that helps prevent infant mortality from other infections, says Topham. “It sort of raises the baseline immunity across the board,” he says.
Though not given in the US, the tuberculosis vaccine introduces humans to what is among the oldest microorganisms that coevolved with humans, says Dr Denise L Faustman, director of immunobiology at Massachusetts General Hospital and an associate professor of medicine at Harvard Medical School.
“These microorganisms live with you for the rest of your life and they’re resetting your genes,” she says. “They have a lot of benefit. When we add back these old organisms, we’re seeing whole protein pathways get reset.”
The BCG vaccine resets sugar pathways. This might help in diabetes and might also prevent Alzheimer’s disease because neurons die after losing sugar, an energy source.
Faustman presented preliminary data from a randomised controlled trial this week at a conference in San Diego. This shows that after five years of taking the BCG vaccine six times, cognitively normal middle-aged adults with a form of Type 1 diabetes had significantly lower levels of two types of protein that play a large role in Alzheimer’s disease compared with those who didn’t get the vaccine.
The use of vaccines as tools to reduce dementia or cancer survival rates isn’t prime time yet and requires more research. Meanwhile, don’t worry about strong side effects you might get from certain vaccines. They are the broad, non-specific response of your body, which is bolstering your immune system.
“We always talk about the downsides of vaccination but there are some unexpected upsides,” notes Topham.
The Wall Street Journal
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