WILTIMS #176: Vaccines PLUS

Today we started off with a series of lectures on congenital and genetic diseases which, though informative, were not super big on interesting anecdotes. The last lecture was on vaccines and it was actually pretty cool to approach this topic now that I know a little more about the immune system. If you want my views on vaccine safety etc, please see my previous post on the subject, or any of the countless reputable online resources on the subject or [in pharma advertisement voice] talk to your doctor.

Cowpox on the hand of the milkmaid, Sarah Nelmes

First a little set-up from things we learned last year: The most famous example of vaccine development is that of the smallpox vaccine in 1796 by Edward Jenner, with the help of an unconsenting minor, a milkmaid, and Blossom the cow. Jenner (and several other people at the time) noticed that milkmaids that had been exposed to cowpox (similar to smallpox but much less virulent in humans) had little to no reaction to exposure to smallpox. Being the good, if less-than-ethical scientist, Jenner needed to test that this exposure was key to their immunity, so he did the obvious thing and tested it on his gardener's 8 year old boy. After inoculating him with cowpox pus from a milkmaid (who was infected by Blossom), the boy was exposed to smallpox and thankfully never developed the disease.

TIL: The idea behind the cowpox-smallpox vaccine is that, since cowpox is similar to smallpox, but not very good at attacking humans, the immune system will easily combat the disease and store up weapons in the adaptive immune system that can attack either virus equally well in the future.

Attenuated vaccines use the same approach. Scientists take a nasty human pathogen and grow it in cells from another species, like monkeys. The virus/bacterium mutates over many generations until it is better at infecting monkey cells. Hopefully, these changes came at the price of the bug losing its virulence towards humans. This is the equivalent to turning smallpox into cowpox to give the immune system an easy practice target. Attenuated vaccines are generally not used with immunocompromised patients because in very rare cases, the patient can develop the full blown disease if a few of the mutated viruses/bacteria mutate back. This is not a problem with immunologically healthy people.

Adjuvants are another group of compounds about which you may have heard when talking about vaccines. These are substances are added to vaccines to get the immune system to treat your fake threat seriously. Since non-attenuated vaccines are usually composed of just a small piece of a surface protein of the targeted virus/bacterium, the immune system will recognize it as foreign and log it as a possible danger. But the immune system is also smart enough to look around and see that none of the other markers of an infection are present, so it will hold back its biggest weapons for more seemingly serious threats. So scientists add compounds that mimic (or are straight-up copies of) parts of other real threats to trigger a proper immune response that will give the vaccine material the welcome it deserves. These adjuvants often include an aluminum salt or some lipid-like organic molecule.