Smallpox for example and Polio (almost)
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Viruses are incredibly small and are very good at hiding, some can hide and go dormant for a very long time meaning they can evade a vaccine.
Both of these efforts you have mentioned took billions of dollars and decades of hard work. It is not just about the money but also the political capital needed to prioritize vaccinations all over the world. If just a single region is not vaccinated enough the virus will not be eradicated. Some of the efforts involved in these vaccination programs have involved negotiating ceasefires in civil wars and open up closed areas to health workers. It have been an enormous effort to complete just one of these programs. So we are prioritizing each virus one by one in order to focus all our efforts on a single program instead of spreading out our efforts making half attempts at each and failing.
There are a huge number of things that need to fall into place to make a virus a candidate for eradication:
Lack of non-human vectors
Slow rate of mutation
Relatively cheap, stable and easily stored vaccine that provide long term immunity
Global effort to role out these vaccines nationwide, or even worldwide
Good disease surveillance
If any one of these pieces aren’t in place, then eradicating a disease is a hugely daunting task that you could be forgiven for saying is outright impossible.
the a effort it took to do thatot small pox and polio took several decades and several billions of dollars and it was primarly accomplished by ensuring the general population is immunized.
as it turns out if a disease no longer has a viable vector to transmit or manifest symptoms it stops being able to spread efficiencty and “stalls out”, Extend this effort for a couple of decades and all current strains die out.
Smallpox was exclusively a human disease. (Yes, cowpox & monkeypox are cousins.) We “only” had to get enough people on Earth vaccinated [decades], then vaccinate *around* sick people for a while, before it ran out of places to live.
That’s called ring vaccination – everyone nearby the patient who hasn’t already been vaccinated or had smallpox is vaccinated. Works best in a small-town atmosphere as opposed to a city.
The World Health Organization had teams that would fly to areas of reported smallpox to vaccinate.
Things like “the common cold” or “the flu” change quickly and substantially, plus can have animal hosts (bird flu, swine flu).
To eradicate a virus, there are a lot of factors that need to be taken into account especially if we want to do it globally.
-The intention and capital and socio-political climate as someone mentioned.
– there should be consensus among different countries and govts for it to be considered
– all diseases are based on three factors:- the agent(microorganism), the host (humans) and the environment, the more we know about these three, the more “amenable” to eradication the disease becomes.
So for eg if the random source of the infection is the most important factor in spread and strength of the infection, then that’s easier to target and eradicate.
If we know only a single vector(like mosquito) can carry that disease, it’s easy to target- kill mosquitoes (seriously fuck mosquitoes)
If there’s no particular source and the problem lies in disease transmission from person to person, then the focus would be to decrease transmission, which is much harder as a target.
Plus if the organism, especially the virus is more prone to mutation, etc, it becomes much harder to make vaccines that will last a long time
You need money, time, scientific know-how, knowledge about the whole process, need govt support, international support, so it’s quite hard to do.
One factor is the rate at which the virus can mutate. Another is the number of species that can be affected.
So for instance, flu mutates quickly and it crosses species. So because it can infect so many different species it has a lot of opportunities to mutate. That makes it almost impossible to develop a universal flu vaccine.
Fortunately, flu is mostly season. So in the US, we look for the flu strains prominent in Australia earlier in the year before the US flu season starts. They make a vaccine that prevents the Australian version and other similar versions. Sometimes the virus mutates enough between the Australian flu season and the US flu season that the vaccine that was developed for the US isn’t as effective.
Australia tends to look at flu in southeastern Asia to develop their vaccine.
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