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Most of the vaccines that we’re familiar with are one of two types: live-attenuated or inactivated. Live-attenuated vaccines are sometimes referred to as having “live virus,” which has caused a great deal of misunderstanding in the general population. The terminology is not exactly a misnomer, but it’s not quite literal either: live-attenuated vaccines are often developed against viruses—which, by nature, can’t be killed because they are not, in fact, alive. Viruses do, however, can only replicate a finite number of times before they are essentially rendered unable to infect. A live-attenuated virus is developed by taking a “live” virus that’s fully capable of replication and basically putting it through the paces in order to weaken it. This is achieved by passing the virus through a series of test tubes, perhaps hundreds of times, while periodically checking to be sure the virus hasn’t smartened up and mutated in response. To be vaccinated with a virus in its weakened state allows the body to recognize the virus in its true form and promotes a strong immune response; as would occur in an active infection.
That being said, vaccines can still be created from inactivated—loosely dead—viruses, too. This option is generally regarded as a safer bet for people with compromised immune systems who would therefore struggle to even fend off a weakened version of a virus. Inactivated vaccines are made from exposing disease-causing microorganisms to agents like formaldehyde, or conditions like high temperatures, that render them incapable of causing infection—what you might call dead. While these vaccines can’t cause infection, they also don’t initiate the kind of immune response that live-attenuated vaccines do, so the immunity they provide doesn’t last as long, and therefore the vaccine may need to be repeated (think “booster” shots). Similarly, there are also subunit vaccinations which contain only the antigenic components of a pathogen, rather than the entire cell. Using only the antigenic part of a pathogen is not always a guaranteed way to create immunity because knowing which of those antigenic properties the body will form a response to can be difficult to ascertain.
Then, there are vaccines for toxins, which may be used for prevention or treatment, such as the vaccines for tetanus, pertussis and diphtheria—which are often given at the same time but in different relative doses. In children under age 7, it’s given as DTap ( where the capitalization of the D and T represent a higher ration of tetanus and diphtheria vaccine) and later doses are given as Tdap—colloquially referred to as a “tetanus booster,” which a child usually gets around age 11, and adults might get if they cut themselves on a rusty tool.
Developing vaccines—and getting them approved for use—is a process that takes years even without controversy. A contemporary example would be the baseless link between autism and the vaccine for measles, mumps and rubella (MMR) which was proposed by Andrew Wakefield. Although the link he claimed—along with his work and whatever reputation he may have had prior—has been discredited by the scientific community, the misinformation has become a stubborn part of the public consciousness. It has also lent itself to a generation of children who are under-immunized, if not lacking immunization altogether. The implications extend far beyond individual children, of course, as evidenced by measles outbreaks over the last decade or so. The CDC had documented measles as being eliminated in the U.S. in the year 2000. In 2014, there were a record number of measles cases in the U.S.: 667—the majority of which were unvaccinated individuals, many of them children.
Measles is hardly the only infectious disease controlled through vaccines: smallpox was effectively controlled by subsequent refined iterations of Jenner’s vaccine, and was in fact so successful that the WHO declared it eradicated in 1980. Rabies, a disease which is nearly always fatal in humans, was long ago deemed too risky for people to attempt to inoculate themselves against. Louis Pasteur and Émile Roux (the former of which is most remembered for his developing pasteurization) developed an inactivated rabies vaccine in 1885.
It was at first inconsistently effective and carried many risks, and because Pasteur kept others from reviewing his research, he was permitted to tout a narrative of success—one which was not supported by data. It was only after his death that scholars realized Pasteur’s initial success with his rabies vaccine was perhaps more of a lucky break than tried-and-tested science. And in fact, as Pasteur was not a licensed physician, had he not been so lucky he could have been prosecuted. But, it was his vaccine that became the basis for the chemically inactivated version which is used not just to prevent rabies, but treat exposures.
Despite the history of discourse surrounding them, the fact remains that vaccines work. Unlike many who pioneered their development, we now have a much better understanding as to how and why they do. Of course, as we have evolved in our fight so too have the organisms. We would expect this, as we would expect new infectious diseases to present themselves.
The future of vaccines will require us to assimilate new technology and our increased knowledge base to continue to innovate. And we already are: some researchers have already started using viruses and bacteria as vectors for the delivery of immunogenic proteins of microorganisms like HIV—which simply cannot be attenuated enough to be safe (live-recombinant vaccines). Beyond the cleverness of the Trojan horse strategy, DNA vaccines—which involve genetically engineering antigens—are in development, too.
If resources for scientific inquiry are to become scarce in the years ahead, to think that researchers will need to turn their focus upon a resurgence of diseases that were once well-controlled through vaccination—as a result of socio-political machinations—is not just disappointing, but terrifying and for many, downright enraging. There are greater present threats, no doubt many of which have yet to reveal themselves fully to us. Like Jenner, we may be working partially in the dark; witnessing the effects of something we don’t yet have the means to illuminate. But we have shed light upon many such murrains in the past. It should be our task to continue to light up the path as we forge ahead. But if we forsake history, we may find ourselves constantly turned around; striking a match to relight that which we should never have permitted to burn out.
Abby Norman is writer based in New England. She’s currently working on a memoir for Nation Books and is the weekend science editor at Futurism. Her work has been featured in The Rumpus, Atlas Obscura, The Establishment, Cosmopolitan, Seventeen, Medium, The Independent, and others. She’s represented by Tisse Takagi in New York City.