Eradicating a virus!

Eradicating a virus!

There is some confusion about why we are still collecting money for polio when we keep seeing in the news that it has been eliminated.

Well of course things are never as straightforward as we would like. It is good to be positive and see what a success the polio campaign has been but it would be very wrong to relax too soon and quickly go back to the 1980s.

There were 3 different strains of the wild polio virus, Types 2 and 3 have not been contracted by anyone in the world for more than 3 years which is an enormous success.  It has saved around 18 million people from some form of paralysis.

BUT  type 1 infections are still being reported in Afghanistan and Pakistan (30-40 a year reported) 

AND

This is where it gets a bit complicated,  

We have been using a live oral vaccine against the 3 types because it was effective, easy to administer by unskilled people, robust and very cheap to make and was key to reducing 350,000 cases a year (1988) to less than 40 today.

However, although extremely effective in the big picture, there is a problem with the live vaccine, the vaccine virus can in rare cases (about 1 in a million), mutate and get back into the wild and cause cases of ‘Circulating Vaccine Derived Polio’. This has happened.

We are still getting small outbreaks of Vaccine Derived Polio in areas that have previously been declared polio free.  Currently there are circulating vaccine derived infections in the DRC, NIger, Nigeria, Somalia, Mozambique, Papua New Guinea and Indonesia.  However the total number is only about 100.

There were 2 cases in Europe in 2015.  And there have been more than 90 cases in Syria during the worst of the fighting due to a collapse of the vaccination program and unsanitary conditions.

Vaccine Derived Polio can easily be eliminated by using an inactivated virus which most countries have now switched to, but this has to be given by injection which needs trained people and costs more to deliver.  This means that a lot of newly born children in poorer countries or remote areas are not getting this and are at risk from infection.

And one dose of the vaccine only protects 50% of recipients.  You need 3 doses to protect 99%.

If ignored, it is possible that Type 1 or a vaccine derived virus could become a new epidemic and so although we have nearly eliminated polio, we must keep vaccinating children for many years yet.

Hence the need to continue to fund a massive world wide child vaccination campaign.

There really have to be zero cases of any type, everywhere, for at least 3 years before we can relax and consider polio a thing of the past.  And as long as we have strains in labs, there will always be a risk of them getting back into circulation.