.

       Parasites: These can be single-celled like malaria, which is a lot larger and more complicated than bacteria are. Parasites can also include worms that infect you or even tiny insects like bed bugs or scabies. We haven’t been successful at making vaccines for many of these but are now having some success with making vaccines for malaria.

       Fungi: These are effectively the mini cousins of mushrooms. They include molds and yeasts. Infections may be from the environment, say from a dust storm in Arizona that can spread Valley Fever, a fungal infection, from the sand and dust. There haven’t been any approved fungal vaccines.

       Prions: Like viruses, prions also aren’t really alive, and they’re even smaller. They’re just crumped proteins that can cause other proteins of the same type to crumple up in the same way. This type of infection causes Mad Cow Disease and a few other diseases, but they’re incredibly rare. We don’t yet have any vaccines for prion diseases in humans (but there is some promising work for animal diseases).

       The oldest type is a similar but alive (or replicating) bacteria or virus that shows our immune system what the danger is without causing us any harm.

       Another tried-and-true method is to take killed, whole bacteria or viruses. These won’t be able to infect us but will show our immune system what to watch for.

       Other vaccines use small proteins or sugars, found on the outside of bacteria or viruses, that can be used to recognize pathogens.IS THIS INGREDIENT SAFE?Vaccines go through rigorous multi-stage testing to ensure they prevent disease and are safe without worrisome side effects. Once vaccines are approved, they continue to be watched for any signs of any problems. Chapter 5 looks more closely at the vaccine testing and manufacturing processes.The ingredients in vaccines are carefully monitored to ensure they don’t have worrisome side effects. The ingredients are clearly listed in the insert that comes with the vaccine. If you ever have any questions about any ingredients and whether you might be allergic to one, you can discuss this with your doctor or healthcare provider.After vaccines are approved by government agencies, including the Food and Drug Administration (FDA) in the United States, they are still monitored for any signs of problems. Anyone who is vaccinated in the United States can report any side effects to a national database that watches for and tracks patterns and serious events.The manufacturing of vaccines is also watched closely. There are ongoing inspections and monitoring of vaccine production facilities by the FDA in the United States and by other independent government organizations in other countries. Around the world, the World Health Organization (WHO) also assesses factories before they begin production for quality, safety, and efficacy. Only factories that are continually inspected and approved for production can make the vaccines.Once vaccines are produced, they undergo testing again. Vaccines are made in batches called lots. Samples from every single lot must be tested to ensure they have the pure, potent, and safe ingredients they are intended to have. No vaccine lot can be distributed until it is released by the FDA. Other countries have similar regulations. If a problem was found in a vaccine from one lot, the entire lot can be recalled.Once vaccines are released, they have to be packaged and stored in certain conditions to keep the vaccine from deteriorating. Many vaccines require what is called cold chain, meaning they have to be kept within a very specific range of cold temperatures all the way from factory to delivery for vaccination. That way, you can feel assured that the vaccine you receive is still potent when you receive it.

       Some vaccines are made against the toxins that bacteria release to make us sick. The vaccine includes something similar and benign, called toxoids, which don’t make us sick, in order to teach our bodies to recognize toxins.

       Two new types of vaccines have been used so far for viruses — viral vector vaccines and vaccines made from genetic material, like mRNA. These vaccines carry the genetic instructions into our cells in order to build a protein that our immune systems can use to recognize a pathogen.