In 1796, the scientist Edward Jenner injected material from a cowpox virusinto an eight-year-old boy with a hunch that this would providethe protection needed to save people from deadly outbreaksof the related smallpox virus. It was a success.
The eight-year-old was inoculatedagainst the disease and this became the first ever vaccine. But why did it work? To understand how vaccines function, we need to know how the immune systemdefends us against contagious diseases in the first place. When foreign microbes invade us, the immune system triggersa series of responses in an attempt to identifyand remove them from our bodies.
The signs that this immuneresponse is working are the coughing, sneezing,inflammation and fever we experience, which work to trap, deter and rid the bodyof threatening things, like bacteria. These innate immune responsesalso trigger our second line of defense, called adaptive immunity. Special cells called B cells and T cellsare recruited to fight microbes, and also record information about them, creating a memory of whatthe invaders look like, and how best to fight them. This know-how becomes handy if the same pathogeninvades the body again. But despite this smart response,there's still a risk involved. The body takes time to learnhow to respond to pathogens and to build up these defenses. And even then, if a body is too weak or youngto fight back when it's invaded, it might face very serious riskif the pathogen is particularly severe. But what if we could preparethe body's immune response, readying it before someone even got ill? This is where vaccines come in.
Using the same principlesthat the body uses to defend itself, scientists use vaccines to triggerthe body's adaptive immune system, without exposing humansto the full strength disease. This has resulted in many vaccines,which each work uniquely, separated into many different types. First, we have live attenuated vaccines. These are made of the pathogen itselfbut a much weaker and tamer version. Next, we have inactive vaccines,in which the pathogens have been killed. The weakening and inactivationin both types of vaccine ensures that pathogens don't developinto the full blown disease. But just like a disease,they trigger an immune response, teaching the body to recognize an attack by making a profileof pathogens in preparation.
The downside is that live attenuatedvaccines can be difficult to make, and because they're liveand quite powerful, people with weaker immune systemscan't have them, while inactive vaccinesdon't create long-lasting immunity. Another type, the subunit vaccine, is only made from one partof the pathogen, called an antigen, the ingredient that actually triggersthe immune response. By even further isolatingspecific components of antigens, like proteins or polysaccharides, these vaccines can promptspecific responses. Scientists are now buildinga whole new range of vaccines called DNA vaccines. For this variety, they isolate the verygenes that make the specific antigens the body needs to trigger its immuneresponse to specific pathogens. When injected into the human body, those genes instruct cellsin the body to make the antigens
. This causes a stronger immune response, and prepares the bodyfor any future threats, and because the vaccine only includesspecific genetic material, it doesn't contain any other ingredientsfrom the rest of the pathogen that could develop into the diseaseand harm the patient
. If these vaccines become a success, we might be able to buildmore effective treatments for invasive pathogens in years to come. Just like Edward Jenner'samazing discovery spurred on modern medicineall those decades ago, continuing the development of vaccines might even allow usto treat diseases like HIV, malaria, or Ebola, one day.
April Fools' DayAOCTiger Woods