How do we know a vaccine for COVID-19 is even possible?

Entirely non-political question. My biology education isn’t what it could have been.

Why are we taking it for granted that it’s only a matter of time before we get a COVID-19 vaccine? It would be terrible if we never did, but that’s a fallacious appeal to consequences.

There’s no vaccine for the common cold (which AFAIK is a coronavirus). There’s no vaccine for herpesviruses, for syphilis, for enteroviruses. There’s no vaccine for most of humanity’s microbial pests. Why some and not others? How do we know which bucket COVID is in?

The common cold is not a coronavirus. Or more to the point, it’s not a virus. It’s thousands of different viruses. Some of those viruses (I think the number I saw was 15%) are coronaviruses, some are other varieties.

There are multiple reasons why we don’t have a vaccine for the cold. One of them is that large number of different viruses. Even if we made a vaccine for the top five most common, or whatever, it’d make almost no difference. The other reason is that the common cold isn’t a big deal. Like any medicine, a vaccine must clear safety standards, such that it’s safer than the disease it works against. Unlike other medicines, a vaccine must be many times safer than its disease, because you give the vaccine to healthy people, who might or might not have ever encountered the disease in the first place. For a disease as minor as the cold, that’s an awfully low bar to limbo under.

To put it in context, suppose that we had a working vaccine for COVID-19, but its side effect was a few days to a week of a runny nose. The world would be all over that. Now suppose that we had the same side effect for a cold vaccine: Why would you bother?

We don’t, but there’s no particular reason to think it’s impossible, either. There is a vaccine for a canine coronavirus, and they were well on the way to developing one for SARS before the virus died out naturally, so vaccines for coronaviruses in general are certainly possible. Nobody, as far as I know, has tried to develop a vaccine for the various coronaviruses that cause common colds (there’s more than one, and not all common colds are caused by coronaviruses, so it would be a ridiculous amount of trouble and expense to eliminate some versions of an illness that isn’t serious to begin with), so the fact that there isn’t one isn’t evidence for anything in particular.

Similar thread from last week - https://boards.straightdope.com/sdmb/showthread.php?t=893874

If a vaccine were impossible, then how could recovery ever be possible?

No major issue of any kind is non-political. However accepting the spirit of the question as trying to de-emphasize the political aspect, I still challenge the premise that serious people take it 100% for granted there will be a highly effective widely available vaccine for COVID-19 in something like the oft quoted 12-18 months*.

OTOH what % of people are ‘really serious’ ones? I don’t know. A very large number of people, importantly including most media people IMO, cannot think probabilistically. They must set up each question as the competition of fairly binary answers. Hence for example they set up the ‘conflict’ of WHO saying it’s unknown if having COVID antiborides confers immunity, ‘there’s no specific evidence of it’, with Fauci saying, to paraphrase, ‘from what we know of similar disease generally, it’s very likely having COVID antibodies confers immunity to some degree for some period of time but we need to find out more’. Not actually opposing binary views. More like binary thinkers distilling one message down to ‘no immunity’ and the other down to ‘don’t worry, immunity’. Some people mask this inability even from themselves with the mechanism of setting an arbitrary burden of proof (I will assume no immunity without 95%-tile proof there is, or vice versa, I’m just being rigorous). In the real world there could be huge costs of assuming either is true just because there’s no conclusive proof of the other.

The vaccine question I believe is somewhat similar. I’d grant that optimists, and if you’re an elected executive official in any country it doesn’t pay to be a pessimist, have seized on (most) experts’ view that vaccine is reasonably likely in a year or two and turned that into ‘fact’. But thinking people with no particular need to keep a brave or crying face for others (or to promote a political agenda) I think accept that that’s much less than certain.

It’s also unknown if the numerous different efforts to find effective treatments with either existing or new drugs will have success enough to make a vaccine secondary by the time, assuming it ever is, a vaccine is ready.

*it would be a major disappointment if the effort succeeded after say 5 yrs, but that would be much less than it took to come up with various past vaccines, albeit at a less advanced state of the art, and without one particular disease being the target.

Immunity and recovery are different physiological mechanisms.

There are anecdotal reports of people recovering from COVID-19 and then getting re-infected again. I don’t think there are enough of those reports to justify confidence, but if they’re true, it reduce the cause for optimism.

Aside from what HMS Irruncible said about immunity, even if we assume that people who recover from COVID-19 have some degree of immunity from getting it again (which is pretty likely given how immune response to viruses usually works), there’s no guarantee that we can make something artificial that grants such immunity.

Like, there are techniques that we know that have worked in the past, and many people are trying to apply every known vaccination technique, but there’s no guarantee that they’ll work.

12-18 months is a best-case scenario timeline floor. If one of the known techniques for making a vaccine that’s being attempted right now works, we might have a broadly available vaccine as soon as a year. Or it might take longer. Or nothing might work.

Even if there are some people who have recovered and gotten it again, and it’s not just an error in the testing, that still doesn’t mean anything about whether a vaccine is possible. That happens occasionally with many diseases for which we have vaccines. It does suggest that the vaccine probably won’t be 100% effective, but then, it doesn’t need to be.

I remember from somewhere that the number of viruses that cause colds is around 200. And of those (and I learned this only since the current pandemic started) there are only 4 coronaviruses. However, they cause an inordinate number of colds, exactly which fraction I don’t remember, but 15% sounds about right.

This news report on two Korean studies is relevant to the OP:

Revealing S. Korean studies show antibodies could thwart COVID-19 reinfection, spread

There are people who have caught chickenpox twice. Occasionally people don’t hold a titer. For some people, it’s a quirk of their immune system, for some, it’s the fact that they were underexposed in the initial infection, and finally, for some diseases, immunity lasts, but eventually wears off, it’s just that people are protected by herd immunity, and so never realize that immunity has worn off. A tetanus shot, for example, confers immunity for about 10 years, and a rabies shot for about three.

There is a final possibility that the “reinfected” people were misdiagnosed, but because they were hospitalized, were then exposed to other hospitalized people with actual COVID-19, so they recovered from whatever caused their initial illness that was misdiagnosed, then came down with actual COVID-19, which was correctly diagnosed the second time.

Personally, a COVID-19 vaccine that had to be re-administered periodically would not break my heart. Sure, a one-and-done shot would be ideal (or, a one, and one three months later, and done). But one every 10 years, or even every three years, I would certainly get, and not cry over having to go back. Heck, there might even be a combined flu/COVID-19 shot for people due for their COVID-19. Or, if it turned out to be something needed every 10 years, maybe it could be combined with the diphtheria/pertussis/tetanus shot, which for adults is also a shot needed at 10-year intervals. Most adults fail to get it, and it’s the main reason babies too young for pertussis shots end up with the disease (it’s mild in adults, but very serious in babies). Combining COVID-19 with the DPT could start people getting the other vaccinations, finally.

At any rate, people who worry about OMG! reinfections! no vaccine! are thinking too black & white.

There may not be a one-&-done vaccine, but there could be a very useful vaccine, and there will probably be something like .01-1% of people who do not respond to the vaccine-- they get the shot, but fail to acquire immunity. There are some people like that for most vaccines. It doesn’t make the vaccine a “failure” if it works for everybody else. Some people take penicillin, and their strep throat doesn’t go away. It’s rare, but it happens. Doesn’t mean that nearly everyone else’s strep didn’t go away, or that doctors should stop prescribing PCN for strep.

Since several vaccines against coronaviruses causing SARS and MERS were promising enough to reach the clinical trial stage (before the diseases faded out and the money and will to continue testing was lacking), there’s excellent reason to think that one or more Covid-19 vaccines will emerge.

Just how effective they’ll turn out to be in preventing infection and whether they’ll lack significant side effects is still open to question. But there’s little doubt in my mind we’ll see production and administration of such a vaccine on a massive scale, though it seems heavily overoptimistic to expect one by this coming fall.

Succinctly, we’ll either find a vaccine or die trying.

Well, no, we won’t die trying. This isn’t the Bubonic Plague or anything. We’re talking about a disease with an over 99% survival rate.

Or in the USA, a 94% survival rate.