24 - Vaccines.ppt

Vaccines 1 Learning objective • • • • What is a Vaccine ? Characteristics of vaccines. Type of vaccines. Examples of marketed vaccines currently in use. 2  A Vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembl...

Vaccines 1 Learning objective • • • • What is a Vaccine ? Characteristics of vaccines. Type of vaccines. Examples of marketed vaccines currently in use. 2  A Vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism. The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters. Vaccines can be prophylactic (to prevent and protect the body from a future infection), or therapeutic (e.g. vaccines against cancer). 3 4 * The Ideal Vaccine: 5 • There are three forms of vaccines classified according to content: A) Live attenuated vacciens B) Inactivated killed vacciens C) Subunit/fragment vaccines. 6 A) Live attenuated vaccines: - Live virus/bacterial vaccines are prepared from attenuated strains that are almost or completely devoid (lack) of pathogenicity but are capable of inducing a protective immune response. They multiply in the human host and provide continuous antigenic stimulation over a period of time. - These vaccines are produced by growing the virus/bacteria in tissue cultures that will select for less virulent strains, or by mutagenesis or targeted deletions in genes required for virulence. - They should not be administered to pregnant women because of the theoretical possibility that the antigen would harm the growing fetus. 7 B) Killed (inactivated) vaccines: - These vaccines contain killed, but previously virulent, micro-organisms that have been destroyed with chemicals treatment such as with formalin, heat, radioactivity or antibiotics. - Inactivated antigens cannot replicate in the body and can be safely administered to pregnant women. - This type of vaccines may require “booster” doses to maintain immunity. 8 Live attenuated Vs Killed (inactivated) vaccines Live vaccine Killed vaccine Low High single multiple many Duration ** It is also important to knowyears that: Short duration Feature Dose no. of doses - Immunity produced by a live, attenuated vaccine is usually more effective. But the Killed vaccine still safer than live vaccines. 9 C) Recombinant subunit/fragment vaccine: A subunit vaccine is a vaccine that contains isolated fragment (e.g. proteins) from a virus/bacterial, but lacks nucleic acid of the micro-organism. These vaccines expose the body to antigens so it can learn to recognize them without exposing the body to the risk of viral replication and subsequent infection. The primary advantage of using a subunit vaccine is that it is very safe, even in people with compromised immune systems. 10 * How to produce a Recombinant vaccine • Producing a relevant proteins from an infectious agent is done without using the microorganism. the DNA fragment codifying these proteins is isolated and then inserted into a plasmid/expression vector that acts as the vector for the transference. Later, this is inserted in the expression vector (Slide 12). • Most used host cells for expression are: bacteria, e.g. Escherichia coli, and Yeast. • Limitations: sometimes isolating the proteins denatures them, causing them to take on a different shape. The immune system develops antibodies to the denatured proteins, but will not recognize the viral proteins coating the virus. 11 roduction of recombinant subunit/fragment vaccine: 12 COVID 19 vaccines 13 Pfizer / BionTech Sputnik V 14 Pfizer/Biontech COVID 19 vaccine 15 Vaccine preparations available in Oman 16 • Live attenuated: → Priorix = live attenuated strains of Measels, Mumps and Rubells virus – subcutaneous injection → Opvero = live attenuated strains of Type 1,2,3 poliovirus – oral intake • Killed (inactive): → Imovax = inactive strains of strains of Type 1,2,3 poliovirus – IM injection • Recombinant vaccines: → Gardasil is a recombinant vaccine of human papilloma virus (HPV) that helps protect against 4 types of HPV. It helps in procting women from cervical cancer caused by HPV. → Tetavax is recombinant vaccine of Clustridium tetani bacteria toxins (tetanospasmin). The vaccine is a TOXOID used to prevent tetanus. 17 COVID 19 vaccines available in Oman: 18 Learning outcomes • Vaccines are biotech products used for disease protection. • Subunit/fragment vaccine is a safe type of vaccines and is produced by following the principles of recombinant DNA technology. • There are many vaccine preparations available in Oman with different technologies used. Vaccines are used for various purposes: childhood immunization, protection against infectious diseases and COVID 19. 19