Trevor James
The oral polio vaccine (OPV) was developed by physician and microbiologist Albert Sabin in the 1950s. It is a live-weakened form of the poliovirus, which is administered by drops in the mouth. OPV has been instrumental in controlling polio worldwide, with large-scale clinical trials in the Soviet Union and Czechoslovakia in the 1950s proving its safety and efficacy. While OPV has been the primary vaccine of choice in most countries, it was discontinued in the United States in 2000 due to rare cases of vaccine-associated paralytic polio. Today, the World Health Organization (WHO) recommends that all children receive the polio vaccine, and countries with varying levels of immunization coverage and polio risk follow different vaccination schedules.
| Characteristics | Values |
|---|---|
| Type | Oral polio vaccine (OPV) |
| Administration | Given by drops in the mouth |
| Composition | Live, weakened poliovirus |
| Safety | Generally safe, but about 3 cases of vaccine-associated paralytic poliomyelitis per million doses given |
| Efficacy | Reduced the number of polio cases reported each year from an estimated 350,000 in 1988 to 33 in 2018 |
| Usage | Used in other countries with endemic polio or a high risk of imported cases; not licensed or available in the United States since 2000 |
| Advantages | Easier to administer than injectable vaccines, ideal for mass vaccination campaigns, provides better immunity by mimicking natural infection |
| Disadvantages | Can cause vaccine-associated paralytic polio (VAPP) in rare cases (about 1 in 2.4 million doses) |
| Alternatives | Inactivated polio vaccine (IPV), given by injection |
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What You'll Learn
Advantages of the oral polio vaccine
The oral polio vaccine (OPV) is a weakened poliovirus given by mouth. It has several advantages over the alternative, inactivated poliovirus vaccine (IPV), which is given by injection.
Firstly, OPV is easier to administer than IPV as it eliminates the need for sterile syringes, making it more suitable for mass vaccination campaigns. This ease of administration has been crucial in reducing the number of polio cases reported each year from an estimated 350,000 in 1988 to 33 in 2018.
Secondly, OPV provides longer-lasting immunity than IPV. While a complete series of IPV doses is thought to protect individuals for many years, OPV provides both humoral immunity and cell-mediated immunity, which is likely to be lifelong. One dose of trivalent OPV produces immunity to all three poliovirus serotypes in roughly 50% of recipients, while three doses produce protective antibodies to all three poliovirus types in more than 95% of recipients.
Thirdly, OPV has been shown to be highly effective in preventing the transmission of poliovirus. This is important in the global eradication of polio, as the virus has no non-primate reservoir in nature and does not survive in the environment for extended periods.
Finally, OPV has been proven safe for use during pregnancy and in individuals with HIV/AIDS. Large-scale clinical trials in the Soviet Union in the late 1950s to early 1960s demonstrated the safety and high efficacy of the vaccine, leading to the worldwide distribution of the Sabin strains.
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History of the oral polio vaccine
The oral polio vaccine (OPV) was developed by Albert Sabin, a Polish-American physician and microbiologist. It uses a live but weakened poliovirus strain and can be administered orally, either as drops or on a sugar cube. This made it ideal for mass vaccination campaigns, especially in developing countries.
The first successful demonstration of a polio vaccine was by Hilary Koprowski in 1950, with a live attenuated virus that people drank. However, the success of an inactivated (killed) polio vaccine, developed by Jonas Salk, was announced in 1955. Salk's injectable vaccine was deemed safe to use, and a nationwide immunisation campaign began in the United States.
Sabin's oral vaccine came into commercial use in 1961, and mass vaccination in the USA started in March 1961. In 1962, Cuba and Italy began administering the OPV in nationwide immunisation programmes. The OPV had the added benefit of interrupting the chain of transmission, meaning it could stop polio outbreaks. By 1964, the annual number of polio cases in Italy had dropped from 2830 to 842 and continued to decline.
In 1979, Rotary International started a multi-year project to immunise 6 million children in the Philippines. In 1988, the World Health Assembly passed a resolution to eradicate polio. In 1994, the Region of the Americas became the first in the world to be certified polio-free by the World Health Organization (WHO). By 1995, mass vaccination campaigns took place in China and India, and National Immunization Days were coordinated in several European and Mediterranean countries.
In the 21st century, polio cases were brought down by more than 99% worldwide in less than two decades. WHO's South-East Asia region was certified polio-free in 2014, the African region in 2020, and the Eastern Mediterranean region has restricted the virus's reach to a few countries.
Today, both the injected and oral vaccines are used to generate optimal immunity. A baby should receive two doses of the injectable vaccine and one dose of the oral polio vaccine during the first year of life, along with two boosters at 18 months and five years old.
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Countries where the oral polio vaccine is used
The oral polio vaccine (OPV) has been used in many countries around the world, and it played a crucial role in the global effort to eradicate polio. Led by the World Health Organization (WHO), UNICEF, and the Rotary Foundation, this campaign began in 1988 and has helped eliminate polio from most of the world.
- United States: The US used OPV from the early 1960s until 2000 when it switched to the inactivated polio vaccine (IPV).
- Belgium's former colonies: The Democratic Republic of the Congo, Rwanda, and Burundi received OPV as part of human trials in the 1950s.
- Hungary: OPV was introduced in December 1959.
- Czechoslovakia: OPV was introduced in early 1960, making it the first country to eliminate polio.
- Cuba: Started administering OPV in nationwide immunization programs in 1962.
- Soviet Union: Large-scale clinical trials were conducted here in the late 1950s to early 1960s, demonstrating the safety and efficacy of OPV.
- China: Mass vaccination campaigns took place in 1995, and China was declared polio-free in 2000.
- India: Mass vaccination campaigns in 1995, and by 2011, no new cases were reported. India was declared polio-free in 2014.
- Australia: Declared polio-free in 2000.
- Japan: Used OPV until 1980.
- Several African countries: OPV was used in some African countries, and by 2004, cases of poliomyelitis were reduced to a few isolated regions in the west.
- Philippines: Rotary International started a project to immunize 6 million children in 1979.
The choice between OPV and IPV depends on various factors, including the local epidemiology of polio, the immunization coverage, and the risk of poliovirus importation. In countries with endemic polio or a high risk of imported cases, the WHO recommends starting with OPV at birth, followed by a primary series of three OPV doses and at least one IPV dose. In countries with high immunization coverage and a low risk of importation, the WHO advises starting with one or two IPV doses, followed by at least two OPV doses.
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Development of the oral polio vaccine
The development of the oral polio vaccine (OPV) was a significant advancement in the fight against poliomyelitis (polio), a highly infectious disease that primarily affects young children and can lead to paralysis and even death. In the mid-1950s, before the widespread availability of vaccines, polio paralysed 25,000 to 30,000 children annually and caused the deaths of approximately 1,500 children each year.
Several groups worked on developing oral polio vaccines, including teams led by Albert Sabin, Hilary Koprowski, and H.R. Cox. Sabin, a physician and microbiologist, developed a live-attenuated viral vaccine, which used a weakened form of the poliovirus. This vaccine was created by growing the virus in cell culture, specifically monkey cells, and then purifying it. This process resulted in the virus losing its pathogenicity, making it safe for administration while still inducing immunity.
Large-scale human trials played a crucial role in the development and distribution of the oral polio vaccine. By 1958, the National Institutes of Health (NIH) had determined that the OPV produced using the Sabin strains was the safest. This conclusion was based on extensive clinical trials conducted in the Soviet Union, Czechoslovakia, and Africa during the late 1950s to early 1960s. These trials, involving millions of children, demonstrated the safety and high efficacy of the Sabin vaccine.
In 1961, the type 1 and 2 monovalent oral poliovirus vaccine (MOPV) was licensed, followed by the licensing of type 3 MOPV in 1962. The trivalent OPV (TOPV) was licensed in 1963 and became the vaccine of choice in the United States and most other countries worldwide. The Sabin vaccine was preferred due to its ability to prevent the virus from multiplying and its ease of administration, making it ideal for mass vaccination campaigns.
Despite its success, the oral polio vaccine developed by Sabin was not without its challenges. In rare cases, the vaccine virus could revert to its original wildtype form during replication, leading to vaccine-associated paralytic polio (VAPP). This occurred in approximately 1 out of every 2.4 million doses. As a result, in 2000, the United States discontinued the use of the oral polio vaccine, opting instead for the inactivated polio vaccine (IPV). However, the oral polio vaccine continues to be used in many other countries, and efforts are underway to develop genetically stabilised vaccines to replace the Sabin vaccines and further reduce the risk of disease-causing mutations.
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Risks and side effects of the oral polio vaccine
The oral polio vaccine (OPV) is a live, "weakened" form of the three types of natural, or wild-type, poliovirus. The viruses are "weakened" by growing them in cells that are different from the ones they infect in people. This process is called "cell-culture adaptation". OPV is given as liquid drops in the mouth.
OPV is no longer used in the United States due to the risk of vaccine-associated paralytic polio (VAPP). About 1 in every 2.4 million doses of OPV causes paralysis. However, OPV is still used in many other countries, and the World Health Organization (WHO) recommends its use in countries with endemic polio or a high risk of imported cases.
The risks and side effects of OPV include:
- VAPP: In rare cases, the vaccine virus can change back to the original wild-type form during replication, causing VAPP. This can occur in both vaccine recipients and susceptible people exposed to the vaccine virus shed by recipients.
- Allergic reaction: Although rare, some people may experience a severe allergic reaction to OPV.
- Interaction with other medicines: OPV may interact with certain medicines, and precautions or changes in dosage may be necessary.
- Age of the recipient: OPV is not recommended for infants younger than 6 weeks old, as maternal antibodies may interfere with the vaccine's effectiveness.
It is important to note that the benefits of OPV in preventing polio greatly outweigh the risks. Large-scale clinical trials have demonstrated the safety and high efficacy of the vaccine, and it has played a crucial role in reducing the number of polio cases worldwide.
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Frequently asked questions
The oral polio vaccine (OPV) is a weakened poliovirus given by mouth. It was developed by physician and microbiologist Albert Sabin and introduced in 1961.
The oral Sabin polio vaccine is given by drops in the mouth.
The oral Sabin polio vaccine is generally safe. However, in rare cases, it can cause vaccine-associated paralytic poliomyelitis (VAPP). The risk is about 1 in 2.4 million doses.
