Tag Archives: Edward Jenner


Pretty much all we keep hearing these days is that we need a vaccine for COVID-19 but what exactly are vaccines and how do they work?

What is a vaccine?

Quick biology lesson: when we are born, we get an acquired immunity to various diseases through drinking our mother’s milk.  For the most part, this acquired immunity will only last about six months.  Acquired immunity just means an immunity that is conferred on us, rather than made by our own immune system.

A vaccine is something that confers and acquired immunity which may last anything from six months to several years.  A weakened or inactivated form of the pathogen is used in the vaccine to make the immune system react.

As adults, we get a natural immunity by being exposed to various pathogens that our body fights off.  Our bodies produces antibodies that fight disease, and in many cases, once we have the antibodies, they will provide us with an immunity against said disease.  As we know from the doubts about immunity to COVID-19, we don’t always get an immunity.  In any case, it normally takes our bodies about five days to make enough antibodies to really fight an infection, which may be too long in some cases.


There are accounts of smallpox inoculation as far back as the 1500s in China and India.  Other reports say that is started much earlier, in around 200 BCE.  It is thought that the procedure was carried out by variolation – some of the toxin is taken from a recently infected person and rubbed against the skin until there became an open wound.  Variola is the generic name of the virus that causes smallpox, hence variolation.

Over the centuries, many physicians searched for a cure for the often-deadly smallpox, without success. And, as has so often been the case, Western and Eastern medicine did not really converge.  

However, in 1721 in Boston, USA, during a smallpox outbreak, 248 people were variolated.  Six of these people died, so it wasn’t perfect, but the mortality rate for those who had been variolated was lower than for those who hadn’t.  Later the same year, Lady Mary Montagu brought variolation to England.  

In 1770, the English physician Edward Jenner started to investigate the folk law that infection with cow pox would confer protection against smallpox.  (Although it wasn’t known then, the viruses that cause these diseases are from the same family.)

In 1796, Jenner successfully used a vaccine made from cox pox to inoculate against smallpox.  By 1853, a law was passed that made it mandatory for children to be vaccinated against smallpox by the time they were three months old.

Fast forward to 1899 and the British army vaccinated almost 15,000 soldiers against typhoid in the Second Boer War.  

By the late 1940s, vaccines for smallpox, tuberculosis, tetanus, diphtheria and whooping cough had become established.  Despite vaccines for more diseases being discovered since then, there are surprising number of people who don’t take advantage of them – for example, it took until 2002 for polio to be eradicated in Europe.

How do they work?

Basically, vaccines make our immune systems think that we have been exposed to a full-on version of a disease.  

It is very common, after a vaccine is administered, to feel some soreness or redness in the area, and perhaps a low-grade fever.   

Vaccination, Inoculation or Immunisation?

These terms are often used interchangeably, but they are all slightly different.  

Inoculation is where something that will grow is inserted inside the body, not only to protect it against a specific disease but also to help it protect against that same disease in the future.

Vaccination is where a weakened version of the bacterium or virus is put into the body so that the immune system produces antibodies against that weakened version. When the body later meets that same disease, it will readily fight it because it has encountered that weakened version before.

Immunisation is the process whereby the body can respond quickly to a pathogen.  We can have either active or passive immunity.  Active immunity happens when we have been exposed to a pathogen.  Passive immunity happens, for example, when a baby gets immunity from its mother’s milk, or we are given an injection of antivenom after a snake bite.

So there you have it, a very basic guide to vaccines, what they do and how they do it.  Personally, there is no doubt in my mind, once a vaccine has been tested and found safe, I would have them every time.

© Susan Shirley 2020