Oral Polio Vaccination Q and A
Dr. Steffen Bau
What is polio?
Polio is a highly infectious viral disease that can cause lifelong paralysis of limbs and may lead to death in people, particularly children under 16 years of age. If contracted the paralysis is not reversible. There is no cure. Infection can however be prevented by vaccination. There are three strains of polio that can cause the same clinical picture, but immunisation to one type does not protect from the other types.
What does polio do to you?
For most people polio virus infection is asymptomatic. That means they show absolutely no symptoms of being infected. This is what makes it so difficult to control the spread of polio as it doesn’t show most of the time. However, up to a quarter of infected people develop mild symptoms that are easily confused with a normal cold; such as headache, mild fever, throat pain and some diarrhoea. In about 1% of infections the virus attacks the nervous system and causes headache, neck-stiffness and abnormal sensation. This can then go further and lead to permanent paralysis which is often asymmetric, such as one arm or leg. In rare cases if the brainstem is involved and the breathing system is damaged the patient will usually stop breathing and die of polio. Up to half of people that developed nervous system involvement without paralysis will get post-polio syndrome with later-onset weakness and extreme fatigue decades down the line. This also does neither have a cure nor treatment options.
How does one contract polio?
Polio is a faecal-oral disease and spreads like many viruses due to direct contact with the excrement of someone infected. So if people don’t wash their hands properly after going to the bathroom they can infect surfaces, food or water and infect other people that come in touch with those easily. Spending any significant amount of time with a polio infected person has a 100% chance of passing on polio. Once in contact with the virus it gets ingested (eaten) and then starts multiplying in your gut.
Who is at the highest risk of contracting polio?
Polio is very infectious and can essentially infect anybody. However, the most devastating effects it exerts usually in the under 16 year olds when it spreads up the nerves into the nervous system and damages brain or spinal cord areas that control the muscles. At increased risk of contracting and also passing the virus on for longer periods than others are in particular pregnant women, persons at the extremes of age (very young or very old), immune deficient and malnourished people. The unborn baby is usually not getting polio, although it can lead to increased first trimester abortions.
How long does one stay infectious after contracting polio?
Normally the virus multiplies for 7-10 days after ingestion in the gut and is passed on by faeces and saliva before breaking through into the blood system and causing possibly symptoms or paralysis. However, immuno-supressed people can spread the virus for up to 6 weeks.
How can one protect children from this virus?
Vaccination is the only reliable way to protect from the infection and its possible consequences. There are two types of vaccine, the injectable polio vaccine (IPV) and the oral polio vaccine (OPV).
IPV was developed 1952 and a few years later OPV was developed. IPV has a killed whole virus and covers all three polio types, but it mainly works on the antibody system in the blood stream. That mean someone who has received 4 doses of IPV is unlikely to get invasive disease but will pass on the virus on infection in the stool for 7-10 days to others. OPV is an attenuated live virus. This means the virus was altered in its infectiousness and even though it still infects humans cannot cause paralysing polio disease. Antibodies formed to the vaccine virus will cover for the same strain of live polio virus and prevent infection. The difference is this protection already starts in the gut, so if one contracts the polio virus it cannot multiply in the gut and one does not become infectious after exposure.
Why is it that the current vaccination campaigns in 2026 focus only on 10 year and younger?
Wild type polio Type 2 was last seen in India in 1999. Since September 2015 it was declared worldwide eradicated. The previous vaccine, although instrumental in eradicating polio Type 2, had a flaw in that the vaccine could sometimes mutate back to an invasive strain that can cause paralysis. The chance was only 1 in 2.7 million people, but with millions receiving the vaccine – especially in under-vaccinated populations where the vaccine virus could spread easily and mutate over and over – a few vaccine-derived polio viruses appeared worldwide. And as these already appeared in under-vaccinated populations these new mutant polio Type 2 started spreading in the population. To avoid further creation of mutants when there is no further wild-type virus in the world all of Africa removed Type 2 from the OPV and from then on only administered Types 1 and 3 in the routine OPV immunisations, which were not that prone to mutation.
In 2011 a new Type 2 OPV (nOPV-2) was created to fight the mutant polio Type 2 viruses that had emerged. This vaccine is very stable and does not lead to significant amounts of new mutants. This vaccine was first used in outbreaks in 2021 and received the full FDA license in 2023. Since then millions of children throughout the world have been vaccinated with this vaccine in outbreak situations with very good tolerability and few mild side effects only.
In November 2025 Namibia detected a mutant polio Type 2 virus on routine surveillance in a sewerage sample in Rundu. This triggered an immediate vaccination response in December 2026 (Round 0) for Kavango East and West districts. A national campaign followed end of January 2026 (Round 1) to cover everyone that has never received any OPV Type 2 vaccine, i.e. anyone born in or after 2016. Anyone older is very likely to have received OPV-2 before and has protection. Even if not, as even the vaccine virus is quite infectious, vaccinating one person in a household will vaccinate the whole household. And after that round another one followed in February 2026 (Round 2).
Why do we need a third round of nOPV-2?
Published research on the nOPV-22 vaccine shows that the vaccine is very safe. It also indicates that when a child receives only one dose of nOPV-2 the coverage is about 65%. If a second dose is given at least 4 weeks later the coverage increases to 85% and with a third round the target personal cover of 95% is achieved. As Namibia is currently experiencing an outbreak with detection of positive surveillance samples from sewerage in Rundu/Gobabes/Windhoek we know that the virus is spreading within our population. If we do not protect the most vulnerable we will see a reemergence of polio with children being paralysed for life.
Will there be more rounds of nOPV-2?
Possibly. It depends on the coverage achieved in the country. It is the responsibility of the government to protect all children from diseases as much as possible, especially something as devastating at polio. Hence the transmission between people needs to be stopped so that virus dies out and cannot infect anyone else and lead to permanent paralysis. If even one child gets paralytic polio we have failed as society to protect our most vulnerable.Surveillance data will guide on the success of our vaccination.
Do I need to get the nOPV-2 for my child if my child already got the OPV at birth?
If your child is 10 year or younger yes, because your child will only have immunity to Types 1 and 3 but not to the circulating Type 2 virus. This leaves your child unprotected and at risk of contracting permanently paralysing polio.
But do I need to immunise if I don’t live in any of the affected areas?
With the virus having been found repeatedly in Windhoek sewerage and Windhoek being the central hub in Namibia this virus is likely to spread to all regions. If you live in a currently unaffected region immunising now gives you a head start. If you live in an affected region it is even more urgent to get enough coverage to prevent a potentially devastating infection. The virus does not care about man-made borders or separations, be they national, cultural, ethnic, religious, monetary, etc. It will infect anyone on direct contact.
For mothers the are currently pregnant and worried about their unborn not receiving a shot after birth or about being infected when pregnant the following applies. The polio virus can travel through the placenta but it is very unusual for the unborn baby to get sick. Maternal antibodies are transmitted to the baby from 28 weeks gestation. So the baby gets protection from the virus passively through the mother’s immunity. The nOPC-2 virus is safe to get in pregnancy, even though we aren’t planning on vaccinating anyone older than 10 years who has already received the old vaccine containing polio Type 2, the vaccine virus spreads in families and will infect pregnant ladies as well. This only serves to boost the immunity of both mother and unborn baby. The one thing mothers that are pregnant and will miss the vaccines can do is ensure all kids in the household of 10 years or under are vaccinated to prevent spread of the real polio Type 2 virus to their baby once born.
Do I have to worry about my pets and farm animals getting sick?
No! This virus is exclusively transmitted between humans. There is no known transfer to or from animals.
What can I do to prevent infection for my children?
If your children are 10 years or younger get as many vaccine rounds as possible to build immunity and prevent infection. This includes nOPV-2 and IPV. Otherwise hygiene is important. Always wash your hands after going to the bathroom and before preparing food, eating anything or touching the mouth. Ensure safe disposal of human waste. No sharing of eating utensils, cups and straws. Avoid spending time with other kids with flu or diarrhoea symptoms.
Is the nOPV-2 vaccine safe?
Yes. This vaccine has been tested in millions of children worldwide and with very little side effects and good protection from polio. It is much less mutagenic than the initial Type 2 vaccine and so the chance of getting paralytic polio from a mutant from this vaccine is so low that statistically we do not have enough children in Namibia to see even a single case of such extremely rare side effect of the vaccine. Unvaccinated children have a reported chance of developing paralysing polio between 1 in 200 to 1 in 1000 children on contracting polio.
There are indicators on each vial to ensure it is safe to use. Every vial has an expiry date and a colour indicator that shows that the vial is in good condition. Vials that are past expiry or where the colour coding indicates decay are discarded.
Is the vaccine safe for children with immunodeficiency and malnutrition?
The vaccine is safe in malnourished children and actually even more important as undernourished children are at higher risk of contracting infections.
Children with active HIV disease Stage IV or primary immunodeficiencies should not get life vaccines. Neither should children that are on heavy immunosuppressive medicine or cytotoxic agents for cancer treatment. If you have any of those children around or any close family members that belong to those categories please contact your doctor to discuss if this is a contraindication to giving that child or a child in the close household the nOPV-2 vaccine.
What are side effects of nOPV-2?
nOPV-2 is very well tolerated. It is a vaccine that has been around for more than half a century just improved in its ability to mutate on passing on to others. Side effects as with most immunisations range from a mild fever, minor headache, irritability, mild fatigue and mild diarrhoea. These side effects are self-limiting and only of short duration.
In extremely rare cases the virus can mutate back to an invasive paralysing polio. This chance is significantly lower than the 1 in 2.7 million chance with the old polio type 2. Also usually this side effect does not occur in the vaccinated child but in unvaccinated children that get the vaccine virus from other vaccinated children, as the virus mutates a little every time it spreads to another person. So if everyone is vaccinated, then everyone will have the same strain of virus without mutations.
Does it not increase the risk of side effects when I get more than one vaccine?
No, actually the risk is decreased, as the body has already been working on a response and the booster is needed to make it more effective. The chance of contracting paralytic polio decreases with the amount of doses given.
How come we got this polio Type 2 virus?
The world is very interconnected and due to travelling there is constant influx and outflow of the country. As polio is mainly asymptomatic one cannot detect it by checking temperatures of people at the airport or borders like during Covid-19. Someone travelling from Angola has brought the virus in and infected Namibians. In the same way someone travelling from Namibia has meanwhile also brought the same virus to Zambia. How do we know this? Because the sewerage samples are tested for polio virus. If found their DNA gets checked and we detect if it is vaccine virus or mutant or wild type virus. We also can identify what mutations the virus has and so link it to other samples allover the world to detect where it came from. All our neighbouring countries are working together in synchronised vaccination efforts to stop the virus from spreading.
But for this to work we need to vaccinate all children including immigrant children that live on the street!
Correct. The government has teams during the vaccination campaign that will go out and vaccinate any child 10 years or under with nOPV-2 in collaboration with community leaders. They specifically target the impoverished communities where due to lack of sanitation and hygiene facilities the infection can spread much faster and wider.
What if my child missed round 1 or 2 already?
No problem. Vaccinate as much as possible. Every added vaccine until a total of three improves the protection. If that means you only have one vaccine that is so much better than no vaccine at all. Also there might be still further campaigns to fill the gaps. Watch out for announcements.
Please contact me if you have any further questions that have not been sufficiently answered above.
Links, Resources, and Publicity:
https://www.facebook.com/share/1EBFgmPtch/?mibextid=wwXIfr
Health Ministry urges polio vaccination for children under 10 – Informante Web
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