In 1961, type 1 and 2 monovalent oral poliovirus vaccine (MOPV) was licensed, and in 1962, type 3 MOPV was licensed. In 1963, trivalent OPV (TOPV) was licensed, and became the vaccine of choice in the United States and most other countries of the world, largely replacing the inactivated polio vaccine. A second wave of mass immunizations led to a further dramatic decline in the number of polio cases. Between 1962 and 1965, about 100 million Americans (roughly 56% of the population at that time) received the Sabin vaccine. The result was a substantial reduction in the number of poliomyelitis cases, even from the much-reduced levels following the introduction of the Salk vaccine.OPV is usually provided in vials containing 10–20 doses of vaccine. A single dose of oral polio vaccine (usually two drops) contains 1,000,000 infectious units of Sabin 1 (effective against PV1), 100,000 infectious units of the Sabin 2 strain, and 600,000 infectious units of Sabin 3. The vaccine contains small traces of antibiotics—neomycin and streptomycin—but does not contain preservatives. History
In a generic sense, vaccination works by priming the immune system with an immunogen. Stimulating immune response, by use of an infectious agent, is known as immunization. The development of immunity to polio efficiently blocks person-to-person transmission of wild poliovirus, thereby protecting both individual vaccine recipients and the wider community.The development of two polio vaccines led to the first modern mass inoculations.
As a response, a novel oral polio vaccine type 2 (nOPV2) was developed with the aim to provide a safer form of vaccination against type 2 strains with less risk of reverting to infectious polio. Schedule
In countries with endemic polio or where the risk of imported cases is high, the WHO recommends OPV vaccine at birth followed by a primary series of three OPV doses and at least one IPV dose starting at 6 weeks of age, with a minimum of 4 weeks between OPV doses. In countries with >90% immunization coverage and low risk of importation, the WHO recommends one or two IPV doses starting at 2 months of age followed by at least two OPV doses, with the doses separated by 4–8 weeks depending on the risk of exposure. In countries with the highest levels of coverage and the lowest risks of importation and transmission, the WHO recommends a primary series of three IPV injections, with a booster dose after an interval of six months or more if the first dose was administered before 2 months of age. Side effects
The inactivated polio vaccines are very safe. Mild redness or pain may occur at the site of injection. Oral polio vaccine results in vaccine-associated paralytic poliomyelitis in about three per million doses. They are generally safe to give to those who are pregnant, and those who have HIV/AIDS, but who are otherwise well.