By: Shreya Sharma
Vaccines are biological products that play a key role in the prevention of many dangerous, potentially deadly, diseases. While medicines are typically used to cure or treat a disease that an individual is suffering from, vaccines are used to protect the individual from being afflicted with the disease in the first place. They work by stimulating an immune response similar to the one that would occur if the body was actually exposed to the illness, resulting in the production of antibodies. This creates immunity without actually getting the disease. There are four primary methods of producing effective vaccines.
One of the commonly used strategies is weakening the virus itself, allowing it to reproduce poorly once in the body. This technique is used for chickenpox, rotavirus, oral polio, intranasal influenza, and MMR (measles, mumps, rubella) vaccines. Viruses, in a typical infection, cause the disease through thousands of reproduction cycles in the body. However, viruses in a vaccine will undergo less than 20 reproductive cycles. Due to the low amount of reproduction, the virus is not strong enough to cause the disease in the body, but there is enough replication to induce the production of B cells, or B lymphocytes. B cells are a type of white blood cell that fights viruses and bacteria by creating pathogen-specific antibodies. Antibodies bind to the invasive cell’s surface and mark them to be destroyed by different immune cells. The biggest advantage of live, but weakened, vaccines is that life-long immunity can generally be achieved through one or two doses. On the other hand, their use can be limited in that these types of vaccines are not suitable for individuals with compromised immunity, such as people with AIDS or cancer.
Inactivating the virus is another method of making vaccines. The process involves using chemicals to completely inactivate the virus, essentially killing it. While the virus is dead and can not reproduce or cause disease in the body, it is still recognized by the body and immune cells against the disease are created. This process is used for rabies, inactivated polio, hepatitis A, and the influenza shot. Inactivated virus vaccines are very effective for those with weakened immune systems because there is no chance of even developing a mild form of the disease through the vaccine. Unlike live vaccines, however, several doses are typically needed to achieve an appropriate level of immunity.
Rather than using the entire virus, a single portion can also be removed and used as a vaccine. The vaccine itself consists of the protein found on the surface of the virus, and the human papillomavirus (HPV), hepatitis B, and shingles vaccines are created through this method. Using a single portion approach is best when the body’s method of protecting against the disease is through an immune response to only one part of the virus. These vaccines are also effective for those with compromised immunity and generally, two doses are enough to induce long-term immunity.
Bacterial vaccines share some similarities with viral vaccines, but there are also several distinctions. Disease-causing bacterias contain harmful proteins called toxins, which can be removed and chemically inactivated. Once inactivated, they are referred to as toxoids, and can no longer cause disease. This process is used to create tetanus, pertussis, and diphtheria vaccines. Alternatively, the polysaccharide (sugar) coating of the bacteria can be used as prevention against several forms of bacteria is based on immunity to the coating alone, rather than the entire bacteria. Young children, however, require conjugated polysaccharide vaccines, which consist of the sugar linked to its carrier protein. The protein induces a stronger immune response and increase immunogenic memory. Pneumococcal and Haemophilus influenzae type B vaccines are made this way. Additionally, some meningococcal vaccines are as well, but others are made using proteins from the bacteria, rather than the bacterial polysaccharide. Similar to the inactivated viral vaccines, bacterial vaccines are effective for those with weak immunity and require multiple doses for sufficient immunity.
Immunization is responsible for protecting millions of lives and is one of the biggest global success stories. There are currently over 20 vaccines that prevent deadly diseases in individuals of all ages. With these indisputable benefits, immunization should be considered a key human right and a vital tool in global health.