Vaccines are a hot topic. Vaccines bring up lots of discussion, lots of false information, and a vitriolic passion rarely seen in matters of science and pseudoscience. I’m going to start my discussion about vaccines by explaining what they are and what they do. My second post will address some of the false information and controversy (with an added bonus of bringing in my lovely sister’s fabulous point of view as a mom of two!) My final post will answer a question I was asked about whether or not vaccinations are needed after a stem cell transplant.
Let’s talk about what immunizations do and how they do it. Vaccines (aka immunizations) use biological agents to induce an immune response that protects you from that disease. The immunization itself could contain a weakened version of the disease-causing agent (like an inactivated poliovirus to vaccinate against polio), a non-human version of the disease (such as the cowpox virus to vaccinate against smallpox) or a small part of the disease-causing agent (for example, the toxin or a protein on the surface of the disease-causing agent). The vaccine is injected into the body, but it isn’t strong enough or functional so it doesn’t cause the disease, but the body attacks the vaccine’s biological agent using immune cells and develops a “memory” of this infection. This memory is made up of both antibodies and immune cells. Antibodies are shaped like the letter Y and the top part of the Y functions like a puzzle piece that fits together with a complementary piece on the infectious agent (called an antigen). When the anitbody encounters a matching puzzle piece it will bind to the infectious agent and kill it quickly before it can cause disease. Therefore, the effectiveness of a vaccines depends on how good the vaccine is at making a puzzle piece fits the antigen puzzle piece on the infectious agent.
So let’s have an example. The flu vaccine contains small proteins from several flu strains that, when injected, stimulate the immune system to create antibodies against those flu strains. When a person encounters the flu,for example because their neighbor has the flu and sneezed on them, the antibodies and immune memory that were created by the vaccination will attack and neutralize the flu virus before it can infect the cells and make you sick. If the flu vaccine didn’t contain proteins that create puzzle piece antigens that bind to the most common flu strain in a particular year, the flu shot is less effective and more people will get the flu.
Vaccines have done amazing things. They have eradicated smallpox, a deadly disease that had been around for over 12,000 years and killed 30-35% of people who were infected. Eradicating this disease saves the lives of over 5 million people each year who would have been infected and died otherwise. Polio, another crippling disease, has nearly been eradicated with only a few hundred cases in 2012 compared to over 350,000 in 1988. Common childhood diseases like measles and whooping cough have also been decreased considerable, saving millions of lives each year through vaccines. They are truly a modern medical miracle!