Adult Vaccines

Michael Greger (0:00)

We have lots of choices to make about our diet. Add to that doing the right thing when it comes to treating a chronic disease, fighting a virus, or losing weight. And suddenly, our nutrition choices can seem almost overwhelming. Well, I'm here to help. Welcome to the Nutrition Facts Podcast. I'm your host, Dr. Michael Greger. Today we look at the kinds of shots that protect you as you age, and we start with the benefits and side effects of the flu vaccine. Every year, influenza typically kills between 4,000 and 20,000 Americans, though the death toll for the 2017 to 2018 season was estimated at 80,000, making it one of the deadliest in the last half century. Most hospitalizations, 90% of flu-related mortality, occur in those 65 and older, and most over the age 75 Mortality rates for the flu at ages 75 and older are 50 times higher than those below age 65 Nonetheless, the CDC recommends everyone over the age of 6 months get a routine annual flu shot every year, if for no other reason than to help prevent transmission to the more vulnerable. The cruel irony is that older adults, the ones who need protection the most, acquire less robust protection from flu shots due to waning immunity with age. Depending on the season, vaccination typically reduces the risk of getting the flu by about 40 to 50 percent. So in healthy adults, we can say with moderate certainty, we can decrease the risk of getting it from like 2% each year down to just under 1%.

Among older adults, even if you get this similar relative risk reduction from 6% down to 2.4%, since the risk is higher and the consequence is greater, the absolute benefits are greater too.

In the northern hemisphere, the flu season can start as early as September and go as late as March. The problem with getting vaccinated too early in the season is that immunity might wane before the season is over, especially in older adults. So it might be good to wait until October, but getting it any time throughout the season is preferable to not getting vaccinated at all.

Yes, the influenza vaccine can cause Guillain-Barre syndrome, an autoimmune attack on your nerves that can leave you paralyzed for weeks, but so too can getting the flu. There may be one to two additional cases of Guillain-Barre per million vaccinations versus about 17 extra cases per million contacts with the flu virus, so you're much more likely to be temporarily paralyzed by the flu than the flu shot. But since it takes vaccinating about 30 older people to prevent one case of the flu, getting vaccinated would still, in expectation, raise your overall Guillain-Barre risk. But the reason flu shots are recommended is not to lower risk of some obscure autoimmune syndrome, but to reduce the common and potentially devastating impacts of the flu to that extent well beyond just the respiratory infection. In the week following a confirmed flu infection, the risk of having a heart attack shoots up six-fold. The inflammation of infection can destabilize atherosclerotic plastic constrict arteries and make the blood more liable to clot. So might flu vaccination save lives in more ways than one? That's why indirectly the flu may kill up to three times more.

Those who get their flu shots are indeed less likely to die from cardiovascular disease in a given year, as well as all causes put together. In other words, those who get regular flu shots live, on average, longer lives. But who disproportionately gets flu shots? White, married, non-smokers of a higher social class with higher education, higher incomes, and health insurance? You can't tell if it's truly cause and effect until you put it to the test. There have been four randomized controlled trials, flu shots versus placebo shots, in those with pre-existing heart disease. And overall, those who got the real shots had a 56% lower chance of dying from cardiovascular disease, and a 47% lower chance of dying from all causes put together. So flu shots really can be an extraordinary lifesaver.

Whether the observational data showing fewer deaths across the board, even among those without pre-existing heart disease, simply pans out as is of yet unknown. But if you notice for secondary prevention, the randomized controlled trials showed even more protection than the observational studies hinted at.

Given the benefits, overcoming vaccine hesitancy should be as simple as correcting misinformation, but sadly, debunking vaccine myths may actually backfire. Busting the myth that inactivated flu shots, the type given to older adults, can give you the flu surprisingly makes people even less likely to get it. Similarly, correcting the falsehood that MMR vaccines cause autism, or that pertussis vaccination causes as many side effects as people think, paradoxically makes people less inclined to vaccinate. The researchers conclude correcting vaccine myths may not be an effective approach to promoting vaccination.