How to Train Your Immune System

Here’s where we stand: healthcare workers in the Netherlands who got last year’s flu vaccine had fewer cases of COVID-19 than their unvaccinated counterparts. In addition, white blood cells treated with the flu vaccine, with or without the tuberculosis vaccine, demonstrated enhanced immune responses when exposed to the COVID-19 virus.

Where does this lead? It’s a quality known as trained innate immunity: exposure to one vaccine, such as the flu vaccine, will train the immune system to respond to another virus such as COVID-19. However one test-tube study does not prove it will work in the real world. Let’s look at some additional research.

The Flu Vaccine and COVID-19

Several retrospective studies have looked at the flu vaccine and COVID-19. In two studies from Italy, people over 65 who got the flu vaccination had a lower mortality rate from COVID-19. There are several more observational studies, but these studies don’t prove cause and effect.

There are problems doing clinical trials, ethical considerations being one of them; for example, if getting the flu vaccine proves to have a beneficial effect, it puts the people in the study who did not get the flu vaccination at risk. There’s also the possibility that it might have been other factors that were actually beneficial, such as lifestyle. It’s all very complicated.

Other Vaccines and COVID-19

Several studies have reported an enhanced immune response against COVID -19 after certain vaccinations. The polio- and measles-containing vaccines have been identified as stimulating the immune system and providing protection against covid-19. The bacillus Calmette-Guérin (BCG) vaccine against tuberculosis could protect against COVID-19 as well. Both have been investigated as potentially being immune-stimulating against severe upper respiratory infections. In countries where BCG is given on a regular basis, the rates of COVID-19 have remained lower than in countries that no longer use it because tuberculosis has been eradicated for the most part.

The Bottom Line

These are observational studies; there’s a lot of research to be done to find out how vaccinations for one virus can provide benefits against a completely unrelated virus. Trained immunity means immune cells are reprogrammed in some way. The “how” is important because what we may find out is that there’s another way to do it, or research may find other factors such as vitamin D status that complement the vaccinations to enhance trained immunity.

One lesson this foray into trained innate immunity has taught me is that our immune system gets weaker as we get older and must constantly be “trained.” It’s not just diet, exercise, and supplements that help our innate immunity; it seems that exposure to other viruses in the form of vaccines may help protect us against severe cases of COVID-19 and possibly other viruses as well. Right now the simplest way to do that is to get the current flu vaccination. We may not evade catching COVID-19, but having a better-trained immune system may help us avoid the most severe symptoms and possibly even death.

I got my flu vaccination and so did Paula. Talk with your physician and see if it’s right for you. Your body. Your choice. But I hope you’ll do whatever you can to put the odds in your favor.

What are you prepared to do today?

        Dr. Chet

References:
1. medRxiv preprint doi: https://doi.org/10.1101/2020.10.14.20212498
2. Nat Rev Immunol. 2020 June; 20(6): 375–388.