While there are many uncertainties about COVID-19 currently, one of them that’s at the topic of everyone’s mind is immunity. Immunity after infection can range from lifelong to nonexistent. There’s only some glimmers of data about the immunity of this.
What can you do in this situation? Well, the best way to do it is to construct a concept of the model, and assumptions on how immunity works, based on knowledge of your immune system, and information about the viruses, in order to identify how each aspect of the model might work or not work, and from there, set out work to improve the understanding with experimenting and observation.
There is a more complicated form of immunity with this, since large groups of such will jump from the animal hosts to the humans. The 2003 outbreak of SARS is an example of tis.
The immunity comes not from the SARS or MERS models, since those infected a smaller population, but after looking at those who survived the infections, the defenses are supposed to persist for a bit, with two years for SARS, and almost 3 for MERS but, the neutralizing ability of this was declining as well when it was studied.
From these studies, there was an educated guess on what’ll happen with patients that have contracted COVID-19. After you’re infected, there will be an immune response, with some being better than others. The response will over some protection for at least a year, but then the effectiveness will decline.
It’s true that infection creates immunity in most people, and the protection will last for a year or more. Then, the infection will increase the numbers of people within the population. From there, it creates herd immunity. As more become immune to the virus, an infected person has less of a chance of being around people that are susceptible to the infection. The herd immunity becomes pervasive enough it can have an infected person averaging less than the other. This will reduce the cases. If the herd immunity is widespread enough, even in the absence of the measures to slow the transmission, the virus will be contained until immunity reduces, or enough new people that are susceptible to infection are birthed.
The problem with this, however, is that testing is too limited in most cases. If the undercounting is around the same level in other countries, then the majority of people in the world would be susceptible to the infection, and herd immunity is minor currently. Long-term control of the virus does depend on getting people to become immune, through infection and then recovery or through vaccination. How large a majority does depend on other parameters.
There is also the concern of reinfection though. About 9% currently have I some cases. Fi some were reinfections, that does cast doubt on the strength of this.
There is the chance though that’s more likely most of them had a false negative test on the infection, which means that there is an inability to distinguish the new infection from other infections.
For now, it’s reasonable to think that only a minority is immune, even in hard-hit locations. How can this tentative picture evolve as data comes along? There is a chance that it could.
There is a chance that many more are happening than being reported, which means that there is an error in the numbers. There is also the testing debacle as well.
There is a chance that the herd immunity is growing, depending on things, but who knows. The best thing we can do, is to wait and see.