This is from DocLighting in the Covid19 vaccine thread and I could see Covid19 going in a similar direction and becoming just another virus that causes the common cold even if a vaccine is developed or not. With respiratory viruses the possibility of re-infection exists but who cares if it gives you a cold or feel nothing.
So that's an interesting topic: What would happen if there never was a vaccine? OK, so this isn't the first novel coronavirus to emerge into the human population, even if we ignore SARS-CoV-(1) and MERS-CoV. There are four other "endemic" (meaning they existed when we discovered coronaviruses) CoVs. They are called hCoV-229E, NL66, OC43, and HKU1 and they cause colds, about 25% of the colds that you've had have been caused by these. So here are two interesting studies.
The first was done around 1990. They took hCoV-229E and infected volunteers with it. This is acceptable to do because it just causes colds. They all developed antibodies against it. Then they followed those volunteers over a one year period and they all lost their antibodies. So they reinfected the volunteers again with -229E and...a few of them got colds. Some of them did not get symptoms. All of them had detectable viral replication. So this gives us an idea of how coronavirus immunity works. We don't develop long-term sterilizing immunity to respiratory coronaviruses in the way that we do to, say, measles. But we do develop some cell-mediated immunity, which allows us to clear the infection more quickly and to ramp up antibody production quickly again. That cell-mediated immunity probably lasts for a very long time.
The second was published in 2012 (IIRC). In this study, they examined the genome of hCoV-OC43. They found that -OC43 is very similar to bCoV, bovine coronavirus. When they did molecular clock analysis on the genome they determined that hCoV-OC43 jumped from cattle to humans around 1890. So they had a look into the history books to see if anything interesting happened around 1890. Now, just to orient you, the very idea of viruses wasn't even discovered until 1892, so they didn't know that viruses existed in 1890, but there was general familiarity with viral diseases even if they didn't know the cause (influenza, smallpox, polio, measles, chickenpox, rubella, mumps, etc.) In 1890 two interesting things happened. First, there was a global pandemic of a respiratory illness that was blamed on a mycoplasma (a kind of bacterium) resulting in the vast culling of herds. And then that year there was an especially bad influenza pandemic in which a lot of patients presented with neurological symptoms, which isn't typical for flu. It's tempting to speculate that what was actually going on that year wasn't some strange coincidence of some mycoplasma and a bad flu, but rather a pandemic of bCoV that then emerged to hCoV-OC43.
Looking to the present situation, we see that this new SARS-CoV-2 seems to cause mild disease in children and young adults. It's mostly the elderly who are severely impacted. So if we look 3-4 years into the future without a vaccine, we would see that most children would be exposed to this new SARS-CoV-2 (which we might rename to "hCoV-WU19" or something) by the time they are around ten years old. The children would then develop long-term cell-mediated immunity, even if their antibody responses tended to wane over time. Then those children would be repeatedly reinfected with SARS-CoV-2 throughout their lives, but because they have already been infected once, each subsequent infection would be mild or even inapparent. We would then see a new equilibrium. How long would this take? Probably 3-4 years, as I said.
So if it takes longer than two years to get a vaccine against SARS-CoV-2, then it will probably be pretty pointless to keep working on it.
This means that even vaccine with 75% effectiveness which Dr. Fauci said might be available at the end of the year and be able to be administered for those most a risk could be enough to create enough partial immunity that is causes the common cold going forward.
I think it’s high time people wake up and smell the coffee that some have been saying for months, and it sounds like the Swedes are starting to realize: this virus is not going away. We can “flatten the curve” all we want and we should, to not overwhelm the healthcare system all at once, but this thing is here to stay if immunity only lasts a few months. Vaccine or not. Flattening the curve isn’t a strategy that can last forever, though
All that’s going to happen when these countries emerge from lockdown, in 2 days or 2 years, is a gradual climb until there is a big spike. Its smart now, but the EU can’t keep its borders shut forever.
Numerous stories I’ve read this week now emerging of folks being reinfected - and analysis is showing this isn’t just “dead virus” making a resurgence in ones body. We’re going to have to live with it. Hopefully - those who survive one round with it will survive again, but I can’t see this thing just dying out.
I am by no means saying the US is doing anything better than an awful job controlling this - but frankly, I’m not sure what people want them to do, outside of mandated masks and not reopening bars and nightclubs, perhaps. But even those policies cannot last forever. If it didn’t spike now, it would spike in 3 months, etc.
I hope there is some degree of breakthrough in what causes some of the chronic problems in some individuals so we can more accurately assess risk, it is Covid19 causing the multi-organ failure or is it something else being triggered and is an undiscovered risk factor.
In terms or re-infection that might now be possible if the antibodies are gone after 3 months. The question is are these people getting sick or less sick and how contagious would they be. If the latter is true then cell-mediated immunity is working and they would have the anti-bodes for another 3 months and that cycle will continue lessening the virulence of Covid19