Terry M. Bella
Today the word vaccine encompasses many types of vaccines, for Jenner it was specifically linked to creating immunity to smallpox, the variola virus. The word vaccine today refers to several types of vaccines. The health care industry utilizes live attenuated organisms, killed or inactivated organisms, purified subunits, and even recombinant subunits. Each of these works on the same general premise, delivery of an antigen to the immune system in order to teach it about the antigen of a pathogen.
A live attenuated vaccine is the pathogen with a weakened virulence. This reduced version of the pathogen still has the same identifiable characteristics, namely the antigens that a non-attenuated form would have. Thus, the immune system is given the opportunity to interact and develop defense against the pathogen without the threat of a disease state. We protect against smallpox, tuberculosis, yellow fever, polio, chickenpox, rotavirus, and influenza with live attenuated vaccines. This process relies on eliminating the virulence of the pathogen while maintaining characteristics that will induce an immune response. This can be achieved by causing mutations in the pathogen and then selecting for mutants with reduced or eliminated virulence. Considering the nature of mutations, being random, there is the chance that a non-virulent strain mutates and becomes virulent again. This risk is minimal though. Live attenuated vaccines are effective because they maintain their antigens, have adjuvant effects, and are packaged in an efficient delivery system (the pathogen), all of which help to elicit an effective and lasting immune response.
In some instances, the best strategy for a vaccine is to use killed or inactivated organisms. These pathogens have been chemically killed or inactivated without detriment to the antigens. Because they have been killed or inactivated an adjuvant is required to help induce the immune response. Some examples are the polio, Hepatitis A, and whooping cough vaccinations. These vaccines, as well as attenuated vaccines are cultivated in tissue cultures, eggs, media, or, in the case of the smallpox, directly in the skin of an infected calf. After culture, they are rendered inactive or killed and not just attenuated.
In the case of tetanus, vaccines are developed to target the toxin of bacterial origin as opposed to the bacteria itself. This type of vaccine is called a toxoid vaccine. The body develops an immune response to the inactivated version of the toxin, rendering the human insusceptible to the active version of the toxin.
Purified or recombinant subunits may be used as vaccines in cases where the antigen is known. Recall that antigens do not have any virulence, equate them to a group of robbers that all where red hats. The red hat may be used to identify them as robbers, but the red hat poses no threat on its own. The antigen can be thought of as the red hat. This is a very safe way to vaccinate as the pathogen, whether live, dead, inactivated, or attenuated is not introduced to the recipient thus there is no threat whatsoever.
Vaccines are also packaged together for a more effective delivery. Vaccines are now polyvalent or multivalent when possible and necessary. The valence of the vaccine refers to how many immunizations are packaged within it. Some vaccines remain monovalent, meaning that they provide immunity to one specific pathogen. Multivalent vaccines may be immunizing against multiple different pathogens or may contain immunizations for multiple strains of the same pathogen. Parents are confronted with this when immunizing their newborns. Multivalent vaccines are used because they are safe and more effective at achieve the desired outcome, herd immunity. There is a simple explanation for why they are more effective and that is less needles. It is as simple as that, less injections are required thus it is more likely that people are immunized against more diseases. It is less likely that a person will follow through with 5 separate immunizations than it is that they follow through with just one. Thus this increases the likelihood that the population is immunized against communicable diseases, decreasing the likelihood of an outbreak. DTaP is the acronym for an infant multivalent vaccine used in the US. The “D” is for diphtheria, the “T” for tetanus, and the “P” for pertussis.
There is much to be taught and explored concerning the production of vaccines but it is beyond the scope of this unit and likely beyond the scope of a high school curriculum. The real lesson in vaccines centers around how they work, the utilization of the immune system to combat a pathogen.
