Chloe Ramirez
The oral polio vaccine (OPV) is a live, attenuated vaccine that has been used to eradicate wild polioviruses around the world. Developed by several groups, including Albert Sabin, Hilary Koprowski, and H.R. Cox, OPV is administered orally as drops or on a sugar cube. It contains a weakened poliovirus that induces immunity in the gut, preventing infection with the wild virus. While OPV is safe and effective, there is a rare risk of vaccine-derived poliovirus (VDPV) emerging in under-vaccinated populations, where the weakened virus can revert to a form that causes illness and paralysis. In contrast, the inactivated polio vaccine (IPV), developed by Jonas Salk, contains a killed virus and is administered via injection in the leg or arm. IPV has been the only polio vaccine used in the United States since 2000, while OPV is still utilized in other countries with a high risk of poliovirus infection due to its low cost and ease of administration.
| Characteristics | Values |
|---|---|
| Type | Oral polio vaccine (OPV) |
| Virus | Live, weakened poliovirus |
| Administration | Oral drops, or on a sugar cube |
| Immunity | Provides immunity to all three poliovirus serotypes in 50% of recipients after one dose; in more than 95% of recipients after three doses |
| Safety | Safe and effective, but can very rarely mutate into a form that causes disease if it spreads among an under-vaccinated population |
| Usage | Used in countries where the risk of getting infected with poliovirus is high; no longer licensed or available in the United States since 2000 |
| Alternative | Inactivated poliovirus vaccine (IPV) |
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What You'll Learn
The oral polio vaccine (OPV) is a live, attenuated vaccine
OPV has played a crucial role in eradicating wild polioviruses worldwide. It offers several advantages over the inactivated polio vaccine (IPV), which is administered through injection. Firstly, OPV is easier to administer as it eliminates the need for sterile syringes, making it more suitable for mass vaccination campaigns. Secondly, OPV provides longer-lasting immunity than IPV as it confers both humoral and cell-mediated immunity. A single dose of trivalent OPV can provide immunity to all three poliovirus serotypes in about 50% of recipients. However, three doses of live-attenuated OPV are highly effective, generating protective antibodies to all three poliovirus types in more than 95% of recipients.
The immunity conferred by OPV is likely to be lifelong, similar to other live-virus vaccines. It offers excellent protection in the intestine, the primary site of wild poliovirus entry, effectively preventing infection in areas where the virus is endemic. Furthermore, OPV is excreted for a few days after vaccination, potentially spreading to unvaccinated individuals nearby and indirectly providing them with immunity. This feature makes OPV particularly valuable in areas with low vaccination coverage, as it helps to protect vulnerable populations.
However, one potential disadvantage of OPV is the risk of vaccine-derived polioviruses (VDPVs). In rare cases, if OPV spreads among under-vaccinated or immunodeficient populations, the weakened virus can revert to a form that causes illness and paralysis. This reversion can lead to outbreaks of circulating vaccine-derived poliovirus (cVDPV). To address this issue, novel oral polio vaccine type 2 (nOPV2) has been developed to enhance vaccine safety and prevent further cVDPV outbreaks.
While OPV is no longer licensed or used in the United States as of 2000, it continues to be administered in other parts of the world, particularly in countries with a high risk of poliovirus infection. Its ease of administration, low cost, and ability to confer immunity to both vaccinated and nearby unvaccinated individuals make it a valuable tool in the ongoing global fight against polio.
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OPV is no longer used in the US
The oral polio vaccine (OPV) is no longer used in the US because it contains live poliovirus, albeit in a weakened form. In extremely rare cases, the weakened virus in the OPV vaccine can mutate into a form capable of causing disease. This can happen when the virus is allowed to circulate in under- or unimmunized populations for long enough or replicate in an immunodeficient individual. As a result, US health authorities switched to using only the inactivated poliovirus vaccine (IPV) in 2000, which contains a killed or inactivated form of the poliovirus and therefore cannot cause disease.
OPV is highly effective at protecting against polio and tends to be more effective than IPV at mitigating the spread of the disease between people. OPV is also easier to administer than IPV because it is given by mouth as liquid drops, eliminating the need for sterile syringes, and is thus more suitable for mass vaccination campaigns. OPV also provides longer-lasting immunity than IPV, as it provides both humoral immunity and cell-mediated immunity. One dose of trivalent OPV produces immunity to all three poliovirus serotypes in roughly 50% of recipients, and three doses produce protective antibodies to all three poliovirus types in more than 95% of recipients. OPV also creates immunity in the intestine, the primary site of wild poliovirus entry, which helps prevent infection with the wild virus in areas where it is endemic.
Despite these advantages, OPV has fallen out of use in the US due to the rare risk of causing vaccine-associated paralytic poliomyelitis, with about three cases occurring per million doses given. In comparison, polio infection results in 5,000 cases per million of paralysis. The emergence of circulating vaccine-derived poliovirus (cVDPV), a form of the vaccine virus that has reverted to causing poliomyelitis, has also contributed to the discontinuation of OPV in the US.
IPV, on the other hand, is given as a series of shots in the leg or arm, depending on the person's age, and protects against paralytic disease caused by any type of poliovirus, including vaccine-derived poliovirus (VDPV). VDPVs can cause outbreaks in places with low vaccine coverage, and people with certain immunodeficiency disorders can shed the virus for long periods, potentially infecting unvaccinated individuals. However, due to high IPV vaccination coverage in the US and the absence of OPV since 2000, it is unlikely that any VDPV would become widespread in the country.
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OPV is still used in other countries
The oral polio vaccine (OPV) is a live, attenuated vaccine that contains a combination of one, two, or three strains of live, weakened poliovirus. It is administered orally, in the form of drops. While OPV is no longer used in the United States, it is still used in many other countries.
OPV has played a crucial role in eradicating wild polioviruses worldwide, and its ease of administration has made it ideal for mass vaccination campaigns. Notably, OPV provides longer-lasting immunity compared to the inactivated polio vaccine (IPV) and interrupts the chain of poliovirus transmission. These unique characteristics have made OPV a powerful tool in the fight against polio outbreaks.
Historically, OPV was first successfully demonstrated by Hilary Koprowski in 1950, although it was not approved for use in the United States. The vaccine found success in other countries, including Mexico, the Soviet Union, the Congo, and Poland. In 1959, ten million children in the Soviet Union received the Sabin oral vaccine, and by 1960, Czechoslovakia became the first country to eliminate polio with the help of OPV.
Today, OPV continues to be used in countries with endemic polio or a high risk of imported cases. The World Health Organization (WHO) recommends OPV vaccine at birth, followed by a primary series of three OPV doses and at least one IPV dose starting at six weeks of age. This recommendation aims to ensure comprehensive protection against poliovirus.
While OPV is still used in many parts of the world, it is essential to note that the emergence of vaccine-derived poliovirus (VDPV) has led to the development of novel oral polio vaccines, such as nOPV2, which aim to enhance vaccine safety and prevent further outbreaks of VDPV.
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IPV is an inactivated (killed) polio vaccine
IPV, or inactivated poliovirus vaccine, is a killed polio vaccine that does not contain any live virus and therefore cannot cause polio. It is administered through injection in the leg or arm, depending on the person's age, and protects against paralytic disease caused by any type of poliovirus, including vaccine-derived poliovirus (VDPV).
IPV has been the only polio vaccine used in the United States since 2000, with the last use of OPV in April 2016. The switch to exclusive use of IPV was made to eliminate the risk of vaccine-derived poliovirus (VDPV) that can occur with OPV. VDPV can emerge when the weakened virus in OPV spreads among under-vaccinated populations and reverts to a form that causes illness and paralysis.
Jonas Salk developed the first successful inactivated polio vaccine, which was announced and licensed in 1955. By 1961, annual polio cases in the United States had dropped from 58,000 to 161. Salk was committed to equitable access to his vaccine and did not profit from sharing the formulation.
Today, IPV is a critical component of childhood immunization schedules, with children receiving a total of four doses of IPV, sometimes in combination with other vaccines. It is recommended that individuals travelling to areas with a high risk of polio infection receive all recommended doses of IPV before departure.
In summary, IPV is an inactivated (killed) polio vaccine that has been successfully used in the United States since 2000 to prevent polio and eliminate the risk of vaccine-derived poliovirus. It is a safe and effective vaccine that has helped reduce polio cases significantly and is a crucial part of global polio eradication efforts.
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IPV is the only polio vaccine used in the US since 2000
The oral polio vaccine (OPV) is a live, attenuated vaccine that contains a combination of one, two, or three strains of live, weakened poliovirus. It is given in the form of oral drops and has been instrumental in eradicating wild polioviruses around the world, including in the United States. OPV provides longer-lasting immunity than the Salk vaccine, as it offers both humoral and cell-mediated immunity. It also produces excellent immunity in the intestine, the primary site of wild poliovirus entry, which helps prevent infection in areas where the virus is endemic.
Despite these benefits, OPV has not been used in the United States since 2000 due to the risk of vaccine-derived poliovirus (VDPV). VDPV can emerge when the weakened strain of the poliovirus from OPV spreads among under-immunized populations. In contrast, inactivated polio vaccine (IPV) does not contain any live virus and cannot cause polio. IPV has been the only polio vaccine used in the US since 2000 and is given as an injection in the leg or arm, depending on the person's age.
IPV provides protection against paralytic disease caused by any type of poliovirus, including VDPV. It is safe and effective, protecting 99-100% of individuals who receive all recommended doses. As part of routine childhood immunization, children in the United States should receive four doses of IPV to protect against polio. Adults who are known to be unvaccinated or incompletely vaccinated should also complete the polio vaccination series with IPV. Additionally, adults who are fully vaccinated but at increased risk of poliovirus exposure, such as international travelers, laboratory workers, and healthcare workers, may receive a single lifetime booster dose of IPV.
Overall, the United States' switch from OPV to IPV in 2000 has helped eliminate the risk of vaccine-derived poliovirus while maintaining high levels of protection against polio through routine immunization with IPV.
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Frequently asked questions
OPV stands for Oral Polio Vaccine. It is a live, attenuated (weakened) vaccine that is administered orally, usually in the form of drops or on a sugar cube.
OPV contains a live, weakened form of the poliovirus. It is created by passing the virus through non-human cells at sub-physiological temperatures, inducing spontaneous mutations in the viral genome.
No, OPV has not been used in the United States since 2000. The US exclusively uses the Inactivated Poliovirus Vaccine (IPV), which is administered via injection.
OPV has been instrumental in eradicating polio globally. However, in under-vaccinated populations, the weakened virus in OPV can spread and, very rarely, mutate into a form that causes disease. This is known as a Vaccine-Derived Poliovirus (VDPV) or Circulating Vaccine-Derived Poliovirus (cVDPV).
