Vaccines are our first line of defense against disease causing pathogens. Vaccines are usually administered to young children, even though there are several vaccines that are given to adults as well. Vaccines work by stimulating our immune system and train them to fight a specific type of infection. To better understand how they work, let’s take a look at some of the common types of vaccines currently available.
These vaccines have live germs, but they do not cause infection because the germs are weakened versions of the original. These are weakened in the laboratory. Live-attenuated vaccines are very effective in generating a strong immune response. They are also long-lasting and require only one or two doses for a lifetime of protection. Their potency is due to the fact that they closely mimic the natural infection caused by a germ. Some examples of live-attenuated vaccines include rotavirus vaccine, chickenpox, smallpox, yellow fever and measles, mumps and rubella (MMR combined vaccine).
However, live-attenuated vaccines also have some disadvantages. For example, they can create health issues if administered to people with weakened immunity or other serious health problems. Another disadvantage is that they need to be kept in a refrigerated environment. So it’s difficult to store these in remote areas.
These vaccines utilize germs that have been entirely deactivated in the laboratory. However, as the physical structure is still intact, they are able to generate an immune response. Since the immune response is not as strong as that of live-attenuated vaccines, several shots may be required to develop the desired immunity. Some common examples of inactivated vaccines include polio, flu, rabies and hepatitis A vaccine.
These vaccines take an entirely different approach by targeting the toxic substances released by a germ. Toxoid vaccines teach the body to defend itself from the toxin released by the germ and not the germ itself. These vaccines are useful where the threat is more from the toxin rather than from the germ. Some common examples of toxoid vaccines include diphtheria and tetanus vaccine.
Instead of the entire germ, these vaccines use specific parts of the germs to create an immune response. For example, the parts could be a specific protein or sugar found in the germ. Or it could be the outer casing of the germ. Based on their sub-type, these vaccines are also referred to as polysaccharide, recombinant and conjugate vaccines.
These generate a strong immune response, similar to that of live-attenuated vaccines. These also have limited side effects, making them safe for use in people with health issues or weak immunity. The only drawback is that booster shots may be required to provide effective protection. Some common examples of subunit vaccines include shingles vaccine, hepatitis B, Hib (Haemophilus influenzae type b) disease, meningococcal disease, pneumococcal disease, HPV (Human papillomavirus) and whooping cough (part of the DTaP combined vaccine).
Scientists are currently working to develop even more advanced types of vaccines. In the future, we could see DNA based vaccines that will be highly effective, low cost and have fewer side effects.