VACCINES: PRINCIPLES & PRACTICE

What is a vaccine? - an antigenic preparation used to produce active immunity to a disease, in order to prevent or ameliorate the effects of infection by any natural or 'wild' strain of the organism - used to stimulate active immunity and to create an immune memory so that exposure to the active disease microorganism will stimulate an already primed immune system to fight the disease

Basic Types of Vaccines in use Today a. Killed vaccines - preparations of normal infectious pathogenic virus that has been rendered non pathogenic usually done by chemical treatment such as with formalin that cross- links viral proteins b. Attenuated vaccines - live virus particles that grow in the vaccine recipient but do not cause disease because the vaccine virus has been altered to a non-pathogenic form

c. Sub-unit vaccines - these are purified components of the virus, such as surface antigen

Specific Requirements for a Vaccine A vaccine must: ● Produce protective immunity with only minimal side effects ● Be immunogenic enough to produce a strong and measurable immune response ● Be stable during its shel life with the potency remaining at a proper level. Inactivated vaccines are stored in a powdered form and are reconstituted before administration: live, attenuated vaccines require refrigeration

Currently Used Vaccines Influenza vaccine - vaccine currently used by the majority of the world consists of inactivated influenza virus. Several types can be used including whole-attenuated virus particles, partially disrupted virus particles ("split" vaccines) and purified envelope antigens ("subunit" vaccines) Influenza vaccine - vaccine currently used by the majority of the world consists of inactivated influenza virus. Several types can be used including whole-attenuated virus particles, partially disrupted virus particles ("split" vaccines) and purified envelope antigens ("subunit" vaccines)

They aim to induce immunity byproducing hemagglutination inhibition or neutralizing antibodies They aim to induce immunity byproducing hemagglutination inhibition or neutralizing antibodies The vaccine is produced in embryonated hens' eggs, using "high growth" strains developed and provided to the manufactures by the World Health Organization The vaccine is produced in embryonated hens' eggs, using "high growth" strains developed and provided to the manufactures by the World Health Organization

The vaccine is administered intramuscularly with a one-inch needle. Adults and older children should be vaccinated in the deltoid muscle, while children should be vaccinated in the anterolateral aspect of the thigh The vaccine is administered intramuscularly with a one-inch needle. Adults and older children should be vaccinated in the deltoid muscle, while children should be vaccinated in the anterolateral aspect of the thigh

Diphtheria vaccine - No diphtheria-only vaccine is available. The diphtheria vaccine is available as: * DTaP (Diphtheria-Tetanus-acellular Pertussis vaccine) * DTaP in combination with Haemophilus influenzae type b (Hib) vaccine * DTaP in combination with hepatitis B and inactivated polio vaccines * DT or Td (in combination with tetanus vaccine) All DTaP vaccines are available containing no or only trace amounts of thimerosal.

Smallpox vaccine - Currently the U.S. has stockpiles of several vaccines used in the past. The stockpile includes 15 million doses of Dryvax®, a calf lymph-derived vaccine produced by Wyeth, which was recently re-tested and shown to be effective. In addition, in March 2002 Aventis Pasteur announced the availability of approximately 85 million dosesof its smallpox vaccine, also derived from calf lymph. Smallpox vaccine - Currently the U.S. has stockpiles of several vaccines used in the past. The stockpile includes 15 million doses of Dryvax®, a calf lymph-derived vaccine produced by Wyeth, which was recently re-tested and shown to be effective. In addition, in March 2002 Aventis Pasteur announced the availability of approximately 85 million dosesof its smallpox vaccine, also derived from calf lymph.

Hepatitis A - liver disease caused by a virus (HAV). The virus is found in the feces of an infected person. It is easily spread by household or sexual contact with an infected person. Hepatitis B - Hepatitis B is a sexually transmitted disease caused by a virus (HBV) that attacks the liver. The virus is found in the blood and semen of infected men and is spread in the same manner as HIV. Hepatitis B - Hepatitis B is a sexually transmitted disease caused by a virus (HBV) that attacks the liver. The virus is found in the blood and semen of infected men and is spread in the same manner as HIV.

The hepatitis A vaccine is available as: * HAV (alone) * HAV (alone) * HAV in combination with hepatitis B * HAV in combination with hepatitis B (HBV) vaccine Hepatitis B vaccine is available as: * HBV Recombinant (alone) * HBV Recombinant (alone) * HBV in combination with Haemophilus influenzae type b (Hib) vaccine * HBV in combination with Haemophilus influenzae type b (Hib) vaccine * HBV in combination with DTaP * HBV in combination with DTaP (Diphtheria-Tetanus-acellular Pertussis) (Diphtheria-Tetanus-acellular Pertussis) and inactivated polio vaccines and inactivated polio vaccines * HBV in combination with hepatitis A (HAV) vaccine * HBV in combination with hepatitis A (HAV) vaccine

Experimental Vaccines in Development New vaccines with major potential for controlling infectious diseases are at advanced stages of development. It proceeds through discovery, process engineering, toxicology and animal studies to human Phase I, II, and III trials. The process can take more than 10 years, depending on the disease. RotaRix - a vaccine developed by GlaxoSmithKline (GSK)for Rotavirus

Status of vaccine development: - showed an efficacy rate against severe rotavirus diarrhoea of 87% in a clinical study of 1986 infants in Venezuela, Brazil, and Mexico, and is now licensed in Mexico, the Dominican Republic, and Kuwait. RotaTeq, a vaccine developed by Merck, protected more than 95% of recipients from severe rotavirus diarrhoea in a clinical trial of 1946 infants in Finland. Prospects: - Rotavirus vaccines will be ready for use in some additional countries by 2006, but information on their effectiveness in Africa and Asia will not be available until They are expected to be ready for widespread use in immunization programs in Africa and Asia by 2009.

Men A conjugate vaccine - Toxicology studies and animal studies have been successfully completed, and the animal studies suggest the conjugate vaccine is highly immunogenic (stimulates high levels of antibodies against Men A infection) - was designed by the Center for Biological Evaluation and Research of the United States Food and Drug Administration Intended to: - have long-lasting effect - create immunity in infants - allow protection to be conferred in advance

Prospects: A low-priced conjugate vaccine for Men A may be ready for widespread use in the African meningitis belt by 2008 or expected to keep costs as low as US$ 0.40 per dose, making the vaccine affordable for low-income countries. Much of this vaccine-development project was underwritten by a US$ 70 million grant from the Bill & Melinda Gates Foundation

Prevnar Vaccine - A seven-valent conjugate vaccine designed to act against seven strains of pneumococcal disease - eveloped by Wyeth and is licensed in the United States and several other countries, but does not include two serotypes (types 1 and 5) that cause a high percentage of pneumococcal illness in developing countries - Conjugate vaccines is proven to be highly effective & made by linking purified polysaccharides (complex sugars) from the coat of a disease-causing bacterium to a protein "carrier."

Prospects: A vaccine providing effective protection against pneumococcal disease for young children in developing countries may be ready for use in , and could be introduced in such countries provided adequate supply and financial help are arranged.