Question: How do the vaccines work? Isn't it putting part of the disease into you? How come some vaccines hurt more than others?

There are several types of vaccines.

Live, attenuated vaccines
Inactivated vaccines
Subunit vaccines
Toxoid vaccines
Conjugate vaccines
DNA vaccines
Recombinant vector vaccines

Live Attenuated Vaccines

Live, attenuated vaccines contain a version of the living microbe that has been weakened in the lab so it can’t cause disease. Because a live, attenuated vaccine is the closest thing to a natural infection, these vaccines are good “teachers” of the immune system: They elicit strong cellular and antibody responses and often confer lifelong immunity with only one or two doses. The remote possibility exists that an attenuated microbe in the vaccine could revert to a virulent form and cause disease. Also, not everyone can safely receive live, attenuated vaccines. For their own protection, people who have damaged or weakened immune systems—because they’ve undergone chemotherapy or have HIV, for example—cannot be given live vaccines.

Inactivated Vaccines

Scientists produce inactivated vaccines by killing the disease-causing microbe with chemicals, heat, or radiation. Such vaccines are more stable and safer than live vaccines: The dead microbes can’t mutate back to their disease-causing state. Inactivated vaccines usually don’t require refrigeration, and they can be easily stored and transported in a freeze-dried form, which makes them accessible to people in developing countries. Most inactivated vaccines, however, stimulate a weaker immune system response than do live vaccines. So it would likely take several additional doses, or booster shots, to maintain a person’s immunity.

Subunit Vaccines

Instead of the entire microbe, subunit vaccines include only the antigens that best stimulate the immune system. Subunit vaccines can contain anywhere from 1 to 20 or more antigens. The Hepatitis B vaccines is a subunit vaccine.

Toxoid Vaccines

For bacteria that secrete toxins, or harmful chemicals, a toxoid vaccine might be the answer. These vaccines are used when a bacterial toxin is the main cause of illness. Scientists have found that they can inactivate toxins by treating them with formalin, a solution of formaldehyde and sterilized water. Such “detoxified” toxins, called toxoids, are safe for use in vaccines.

When the immune system receives a vaccine containing a harmless toxoid, it learns how to fight off the natural toxin. The immune system produces antibodies that lock onto and block the toxin. Vaccines against diphtheria and tetanus are examples of toxoid vaccines.

Conjugate VAccines

If a bacterium possesses an outer coating of sugar molecules called polysaccharides, as many harmful bacteria do, researchers may try making a conjugate vaccine for it. Polysaccharide coatings disguise a bacterium’s antigens so that the immature immune systems of infants and younger children can’t recognize or respond to them. Conjugate vaccines, a special type of subunit vaccine, get around this problem.

When making a conjugate vaccine, scientists link antigens or toxoids from a microbe that an infant’s immune system can recognize to the polysaccharides. The linkage helps the immature immune system react to polysaccharide coatings and defend against the disease-causing bacterium. The vaccine that protects against Haemophilus influenzae type B (Hib) is a conjugate vaccine.

DNA Vaccines

Once the genes from a microbe have been analyzed, scientists could attempt to create a DNA vaccine against it. Still in the experimental stages, these vaccines show great promise, and several types are being tested in humans.

Recombinant Vector Vaccines

Recombinant vector vaccines are experimental vaccines similar to DNA vaccines, but they use an attenuated virus or bacterium to introduce microbial DNA to cells of the body. “Vector” refers to the virus or bacterium used as the carrier.

I know that’s a lot of information, but there are a lot of different ways to make a vaccine these days!

As for why some hurt more than others, you are pushing liquid into your vein, which increases the pressure and thus this is felt as pain. IF you have a vaccine that is a slightly bigger volume it will hurt more on injection. As for those which start hurting a few hours after the injection (like big ol’ scary tetanus shots) I was told that it hurting was a good sign, and redness around the injection site was too. If this happens in the first 24 hours, it usually means your body is launching a nice strong attack against the vaccine (which is what you want it to do) and this means you will have very good protection against the thing you are vaccinating against

I know with one of the Hepatitis vaccines i had to have 3 jabs and then they had to take blood and test if i had made enough antibodies yet, or whether i needed more jabs. Those didn’t hurt at all, but Tetanus shot did! and you only need one of those every 10 or so years