Immunization

Frequently asked polio questions

Global Polio Eradication Initiative

This guide is intended for distribution to PEI planners and health workers. It contains information about the polio eradication initiative that has proven useful when addressing common questions from governments, media, health professionals and communities. Information in this guide should be adapted for local use and incorporated into local materials and messages as appropriate. Further information can be obtained at the following websites, or through direct contact with any of the partner agencies listed.

Guide to Contents

Polio
What is poliomyelitis?  How is polio spread?  Can polio be treated?

Vaccine Safety
What is OPV?  Is the oral polio vaccine safe/effective for eradication?  Why do some children still get polio after several doses of the vaccine? Isn’t routine immunization sufficient?  Is the polio vaccine in effective in preventing polio?  What is the VVM and how does it work?  Can OPV with stage three or four VVM be used if the expiration date is still valid?  Can OPV be used after the expiration date if the VVM is still valid?  Is it safe to administer multiple doses of OPV to children?  Is the polio vaccine safe for all children, even sick children and newborns? Why are we not using IPV for the eradication effort in developing countries?  What is monovalent oral polio vaccine (mOPV)?  Why has the decision been made to use mOPV?  What is vaccine associated paralytic polio (VAPP)?  What is vaccine derived poliovirus (VDPV)?

Campaign
What is the current status of the polio eradication initiative?  What will it take to eradicate polio?  What are the main risks to achieving global polio eradication?  Why did we miss the 2005 goal to end polio transmission?  When will polio transmission stop/ when will polio be eradicated?  What will happen should transmission continue into 2008 and beyond?  Is there a cut-off point for the global eradication initiative?  Can an individual country be officially certified polio-free?  What is the difference between stopping transmission and global eradication?  Is it really feasible to immunize every child during polio campaigns?  Why dedicate so many resources to polio when it affects so few children, when other diseases like measles and HIV are much more of a threat?  How does the polio eradication effort affect other health initiatives? Which children are most likely to be missed during polio immunization campaigns?  Why are the national polio campaigns held so frequently?  Why do polio vaccinators come directly to people’s houses?  If all the other children are immunized, isn’t it OK to miss a few children?

Outbreak
Key messages around outbreaks.  Why are we seeing polio outbreaks in polio-free countries?  Are the latest outbreaks a major setback?  Could polio spread to other polio-free countries?  Some media reports have blamed the African epidemic on Islamic clerics. Is this fair?

Rumours
Are there any religious objections to the use of vaccines or OPV?  Can polio vaccine cause infertility/HIV/cancer?  Is polio eradication a plot by western governments?
 

Polio Questions

What is poliomyelitis?
Poliomyelitis is an infectious disease caused by a virus. There are three kinds, or serotypes, of poliovirus, known as polio type 1 (P1), polio type 2 (P2) and polio type 3 (P3). Only serotypes P1 and P3 are still found in the wild—the last case of P2 was found in India in 1999.

Initial symptoms of polio infection are fatigue, headache, vomiting and aches in the limbs. Nearly 1 in every 200 infections leads to irreversible paralysis (usually in the legs) while the remaining 199 infections are asymptomatic, or do not show enough symptoms to get medical attention. The poliovirus is silent. This means that polio can be widespread in a community before it is seen in a case of paralysis. Polio mainly affects children under three years of age and can be fatal if it paralyzes the muscles used for breathing. Polio rarely occurs in adolescents and adults.

How is polio spread?
The poliovirus enters the body through the mouth in contaminated food or water, and also through the nasal passages when inhaled. Once the virus enters our body, it multiplies in the intestines and invades the nervous system, damaging the nerves. Polio can cause total paralysis, and, in severe cases, even death.

Can polio be treated?
There is no treatment for polio. Oral polio vaccine (OPV) is very effective in giving children lifelong protection from the virus. Physical therapy and braces can help paralyzed children to regain some function, but nerve damage is permanent.

Vaccine Safety Questions

What is OPV?
Two types of polio vaccine are available: oral polio vaccine (OPV) and inactivated polio vaccine (IPV).
OPV was developed by Albert Sabin, and first licensed in 1962. OPV is made with a live but weakened (attenuated) virus and is administered through the mouth, usually by a dropper, thus it is called an “oral” vaccine. The weakened virus provokes immunity in the human body, but is too weak to cause disease, thus protecting people from future contract with wild (disease causeing) poliovirus. OPV protects vaccinated persons directly and also protects other susceptible persons who are indirectly "vaccinated" as the vaccine virus spreads in the community. IPV is given by injection and protects vaccinated persons as well as OPV, but it is not believed to be as effective as OPV in preventing the spread of polio virus among non-vaccinated persons.

Is the oral polio vaccine safe/effective for eradication?
Yes – the oral polio vaccine (OPV) is safe, effective and the WHO recommended vaccine for polio eradication.

In many countries, UNICEF supplies all the polio vaccine for polio national immunization days. UNICEF only procures vaccine from companies that have been approved by WHO, the international gold standard for quality assurance. WHO required tests continually confirm the absence of hormones or any other substances which would indicate OPV to be unsafe.

Since the Polio Eradication Initiative was launched in 1988, 10 billion doses of vaccine have been sent to over 100 of the world’s poorest countries to immunize children. Because of oral polio vaccine, 5 million children are walking who would otherwise have been paralysed.

N.B. The theory presented that polio vaccine was the origin of HIV, presented by Mr Edward Hooper in his book “The River” (published 1999), was recently aired on Francophone TV. Since the publication of Mr. Hooper’s book, this theory has been widely discredited by the international, scientific community. Epidemiological, biological, and virological evidence all indicate that Mr Hooper’s hypothesis can in no way be substantiated and is incorrect.

Why do some children still get polio after several doses of the vaccine? Isn’t routine immunization sufficient?
Statistically, a child’s ability to convert the oral polio vaccine into immunity (seroconvert) depends upon the environment in which that child lives. In temperate climates or industrialized countries with excellent sanitation and health systems, it takes at least three doses of OPV to for a child to be immunized against polio. In tropical environments or in parts of the world that are less developed, where children may be malnourished, sanitation systems are often poor and health services not widely available, it can take many more doses of the vaccine to ensure that a child reaches the same level of immunity – sometimes more than ten doses of OPV are required.

While OPV is safe, it is not a perfect vaccine. Some children do not initially respond to the vaccine, especially in less developed countries where other infections might compete in the gut with the polio vaccine. Perhaps as many as 4 or 5 out of every 100 children fail to respond to the vaccine after multiple doses and can still develop polio. If these children live in communities where vaccination coverage is low, they have a high risk of exposure and infection. As the number of children repeatedly missed during immunization campaigns goes down, the only susceptible children remaining are those who have had multiple doses of OPV but who didn’t respond to the vaccine and are still vulnerable to the polio virus. So it is expected that as polio cases decrease, the remaining vulnerable children will be composed of many who have had multiple doses of OPV but who did not respond to the vaccine. However, most of the children who get polio are under-immunized. This means that they have fewer than the number of doses thought necessary to protect children in their circumstances from the virus.

Although no vaccine offers 100% protection, when a certain percentage of a population is vaccinated, disease spread is effectively stopped. For many diseases vaccination, just like natural exposure provokes the immune system to effectively defend against subsequent exposures to the disease, thus offering protection against future infections. The PEI relies upon mass vaccination to achieve herd immunity—a term that describes what happens when vaccination or natural exposure in a population (the herd) reaches enough people and causes them to become immune, so a disease can no longer spread. When the disease can no longer spread, it burns out, thus protecting the un-immunized individuals. The general aim of many immunization programmes is to establish heard immunity. The goal of PEI is to establish herd immunity in the remaining populations still affected by poliovirus worldwide thus eliminating the disease from these areas. Once all areas in the world are declared polio free, the virus will have been eradicated.

Is the polio vaccine effective in preventing polio?
Yes. The polio vaccine used in today is the same vaccine that has been used in practically every other country in the world to successfully eliminate the poliovirus. Many of the countries that have used this vaccine, including UAE and Japan, continue to fund polio eradication activities elsewhere.

All batches of vaccine are tested for quality before use. In addition, each vial of OPV has a vaccine vial monitor (VVM) that indicates if the vaccine has been exposed to heat, which can render it ineffective. All personnel working in the polio eradication campaign are trained to examine the VVM and discard any vaccine that might be weakened from exposure to heat.

What is the VVM and how does it work?
OPV is sensitive to high temperatures and loses potency if exposed to heat for prolonged periods of time. A system of refrigeration and coolers, called the cold chain, is put in place to ensure that OPV remains cold through its entire journey until it is administered to a person. Vials of OPV are equipped with heat sensitive labels called the vaccine vial monitor (VVM). The VVM allows health workers to know if the vaccine has been exposed to heat. All OPV supplied by UNICEF has used the VVM since 1997.

The VVM has four stages. The VVM comes in stage one, which remains constant as long as the vaccine is not exposed to heat. With continued exposure to heat, the VVM moves through stages two and three and finally to stage four. Any VVM found to be in either stage three or four should be removed immediately and not be used for immunization.

Can OPV with stage three or four VVM be used if the expiration date is still valid?
No. A late stage VVM is an indication that the vaccine has been exposed to heat long enough that it should no longer be used. There is a margin of safety built into the VVM so that even a late stage VVM might still be potent, but the vaccine has had enough exposure to heat that it should be discarded because it is potentially weakened. Using a vaccine with a late stage VVM is not harmful, but it might not offer immunity


 


 

 

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