Medical Fun Facts Podcast

MFF0023: Immunity

So many possibilities with the letter I but the most obvious one is Immunity.

In common parlance, there are two uses of the word immunity. In nonmedical circles, immunity means protection or exemption from something, especially a penalty, like immunity from prosecution. Diplomats have so-called immunity from prosecution when they transgress many laws in the countries they work in. For example, in Canberra, as a national capital, we have many embassies from other countries and their national staff run up significant debts for parking and traffic offences.

In a medical sense, immunity means the ability of an organism like a human being or an animal, to resist a particular infectious agent or toxin by the specific action of antibodies or sensitised leucocytes.

Bacteria do NOT develop immunity to antibiotics. Bacteria develop resistance to antimicrobials. The mechanisms are very different. I often hear nonmedical people saying they don’t want to take antibiotics because the infection will become immune to the antibiotics. It’s worse when I hear medical practitioners explain it that way to patients. It just spreads misinformation. Using plain language doesn’t mean using the wrong language.

The other thing that peeves me is when people speak about the ‘immune system’ like it is a sentient being and can live separate to our own beings. You hear people talking about their own immune systems making decisions and doing this or doing that. It’s just the immune system. It’s as complex as our endocrine system which is not sentient, nor is our autonomic nervous system.

I really wish biology was compulsory in school. I remember back in grade 9 learning basic human anatomy and physiology. It seemed odd that friends at other schools learnt these things in physical education. I think biology teachers are better at imparting the necessary information.

Anyway, back to immunity. For the vast majority of people, our immune systems are exposed to countless antigens every day so that humoral and cellular immune systems can become more refined and better at protecting us from infectious agents and toxins. With modern hygiene, better food and better health infrastructure, we’re no longer exposed to some infectious agents and toxins that our forebears were. For example, smallpox and polio are largely gone and the viruses responsible for those infections are mostly well contained. Tetanus is not often seen in countries with good functioning economies and health systems. The difference is the advent of vaccines, vaccination and the effect of immunisation on our health.

Not every vaccine is safe, in fact, there are some, where the risks are such that some people must be excluded, e.g., second-generation smallpox vaccine should not be administered to people with severe skin diseases. Mostly though, the vaccines that have been produced in modern times to prevent childhood diseases like measles, rubella, meningococcal meningitis and Hepatitis B are relatively safe. I think people have lost sight of the fact that diseases like measles have a mortality which can occur soon after infection and decades after infection, rubella causes blindness, deafness and brain damage in babies, meningococcal meningitis can be fatal and Hepatitis B can be a prelude to hepatic carcinoma. Did you know the Hepatitis B vaccine was the first vaccine to prevent a deadly carcinoma? The new Human Papillomavirus vaccine is preventing carcinoma not only of the cervix but also throat and rectal carcinomas as unprotected oral and anal sex become more common in teenagers.

Some of the older preparations had potential side effects, like when I was a baby, the old-fashioned triple antigen often gave babies a fever. I suffered febrile convulsions when administered the triple antigen preparation at 2 and 4 months. Mum said she found it very unsettling watching me have these seizures as a baby. I’m glad she didn’t take me to the hospital. When I was a resident, I worked for one pædiatrician who had a standing order that every child seen with a febrile convulsion needed a lumbar puncture.

Sometimes I do wonder if those convulsions had any lasting effect on me. Perhaps I could have been smarter and become an electrical engineer rather than a medical practitioner.

The bottom line is that in general, modern vaccines are safe and the benefits of vaccination are plain for all to see.


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