Question

how many lives have been save by vaccines? summary of a vaccinology topic. foccusing on any vaccine, vaccine development, or safety or the "antivax movement"

Answer 1

Vaccines are man made biological preparations that provides the receiver with active acquired immunity against a particular pathogen. Vaccines are prepared from the live attenuated (weakened) or the killed forms of disease causing microbes, their toxins or their surface proteins. These vaccines will stimulate the immune system of the receiver when he/she is exposed to that particular pathogen and fights and destroys it. Vaccination is an effective method to prevent the occurrence and spread of an infectious disease. Invention of Vaccines play a vital role in preventing the occurrence of many infectious diseases like poliomyelitis, chickenpox, Influenza, measles, mumps, rubella and so on.

Polio Vaccine:

There are two types of polio vaccines, injectable form (Salk vaccine) and oral form (Sabin).Oral polio vaccines are live attenuated vaccines whereas injectable inactivated polio vaccines are killed vaccines. Both these vaccines has remarkably brought down the incidence of poliomyelitis cases world wide.

Vaccine development: The first successful and approved polio vaccine IPV (Salk vaccine ) was developed and came to use in 1950s by Jonas Salk an American physician. Albert Sabin developed Oral polio vaccine and in 1961 it started to be used commercially word wide. This vaccine is listed in the WHO's list of essential medicines(is the list of medications considered to be most effective and safe to meet the health needs) . Three doses of Inactivated polio Vaccine (IPV) provides immunity to 99% of the receivers though the duration of immunity induced by IPV is not certain. OPV which contains live attenuated viral strains are easier to be administered and are suitable for mass vaccination too. OPV provides humoral as well as cell mediated immunity and are found to provide long lasting immunity than IPV.

IPV is based on three virulent strains of polio virus which are type 1 poliovirus (Mahoney), type 2 poliovirus (MEF-1), and type 3 poliovirus (Saukett). These are grown in a type of monkey kidney tissue culture and are then are inactivated with formalin. IPV provides IgG mediated immunity. The risk of bulbar polio, post polio syndrome and viremia are elimated by use of inactivated vaccines which protects the motor neurons OPV, the live attenuated form is produced by passing the virus through nonhuman cells at a sub physiological temperature that causes spontaneous mutation in the viral genome. OPV comes in a vial that contains 10 to 20 doses and each single dose comprises of 2 drops of vaccine. One dose contains 1,000,000 infectious units of Sabin 1 and Sabin 2 that are effective against type 1 and 2 polio viruses respectively as well as  600,000 infectious units of Sabin 3 which is effective against type 3 polio virus.

Vaccine schedule: It may differ in various countries. World Health Organization recommends to administer OPV at birth followed by a primary series of three OPV. Also at least one IPV dose starting at 6 weeks of age and a gap of minimum four weeks between the OPV doses in countries where Polio is an endemic or with high number of reported cases.

Vaccine safety: as discussed earlier both the vaccines (IPV as well as OPV) are effective against the pathogen but OPV are considered to be more effective in relation to long lasting immunity, absence of need for sterile syringes and injection procedure (failure in which can cause vaccine site complications like abscess) as well as feasibility for mass vaccination. Inactivated vaccines too are very safe and common side effects are mild redness and pain at the site of infection. A rare ( 3 per a million doses administered) complication associated with OPV administration is Vaccine associated paralytic poliomyelitis.