Immune or not? seems simple. Apparently it's not

I do not understand the term, immunity, in regards to covid-19. I believe that some vaccines protect us from some diseases absolutely, and for a long time. Occasionally, but not always, we may have to get a booster. But while the vaccine is actively protecting us, we are resistant to infection. Maybe polio is one of those. Also smallpox, maybe, both of which have been virtually eradicated. Measles and DPT vaccines seem to completely prevent infection. Maybe I’m wrong about that, but we never hear anything to the contrary. Is this not the case with Covid-19? When we are vaccinated, are we or are we not protected from infection? Are we immune or not?

I’m not aware of any vaccine that offers 100% protection against infection. Such a thing may be observed in clinical trials of a few thousand people, but when you start vaccinating millions of people, you are guaranteed to see some breakthrough infections.

DTaP vaccines are only 80-90% effective. My niece was fully vaccinated, but still managed to get infected by an unvaccinated/sick classmate.

In a discussion of Covid vaccine efficacy, it was mentioned that the typical annual flu vaccine is a lucky hit if it is better than 65% effective. (And not just because of variants). The idea with flu vaccine is to immunize enough people to interrupt the typical rate of transmission so it does not become as wide-spread as it might.

The 95% effectiveness of the Moderna and Phizer is considered amazingly good, especially for something developed so quickly. However, you still have a 1 in 20 chance of catching the disease in a situation where you would have had a 100% chance without the vaccine. (But the vaccine also means the symptoms should be greatly reduced) Hence, until the disease is not very common out in the wild, wear a mask and cut that 1 in 20 to something like 1 in 100. (Rule of thumb, masks are about 80% effective in some situations) Once your chance of encountering the disease is extremely low, we can all remove our masks.

This is an awesome article - it was written pre-vaccine…

I find that that word is key in this. In the way that waterproof and water-resistant mean two different things in the world of watches, you’re not COVID-proof, you’re COVID-resistant once vaccinated. Measles does actually have the same issue. The fact that you haven’t gotten measles has a whole lot more to do with the fact that most of us have been vaccinated for a long time and thus have mostly eliminated its ability to spread as opposed to you personally being vaccinated. It’s not a binary mechanism. Your body is trained to fight the pathogen, but not guaranteed to win. Occasionally, the virus will roll a 20.

Similarly, my daughter got pertussis (whooping cough) when she was little, even though she was vaccinated. She didn’t have a particularly bad case of it (probably because of the vaccine), but she still got it, and it surprised the heck out of all the medical professionals we saw when her swab came back positive (with one doctor insisting it couldn’t be pertussis, over my suspicions that she had it, because he’s worked as a physician for 30 years, and he’s only seen one case in his life.) They ain’t bulletproof. (I was impressed with the CDC following up with us almost immediately after that.)

It’s difficult to be sure, but the confirmed COVID-19 infection rates after full immunization (i.e. two weeks after the 2nd shot) with pfizer and moderna are crazy low. Something like .001 percent.

It’s probably not that low for infection per se, but may well be that effective in preventing ‘serious infection’, i.e. hospitalization or death

Nothing is ever absolute in biology.

The first problem is a large study can show effects for that large group of people. That population may not be the same as you in some ways. The time under study, exposed variants, lots of other specific details will change.

Despite this, the information is still helpful. But a population study never can say what will happen to you personally. Your body has different ways of fighting a virus. There is immunity because you have specific antibodies and more generalized ways of fighting any pathogen or ones fairly similar to past encounters. There is herd immunity, a kind of protection reducing risk if enough people have some immunity.

You get a vaccination. The numbers show it is effective for most people. They recommend a second shot in a few months since studies show this increases efficacy.

No one really knows how long this immunity will last. This might well depend on the characteristics of further variants which will inevitably arise. It will be very closely watched to see if more shots are needed. Many viruses produce variants which cause fewer problems and do sort of fizzle out. Some variants can be worse and a vaccine may or may not be highly effective against them.

You should get the shot. It will reduce the risk of major problems and hospitalization. No one can say if it will make you immune. You may need more boosters and more information on this will become available.

I’m not sure if I’m comfortable with thinking in probabilistic terms because I’m a gamer, or if I enjoy gaming because I’m comfortable thinking in probabilistic terms. Probably a bit of a virtuous cycle. (I tend to think of vaccines as granting massive saving throw bonuses rather than requiring the vaccine to roll a nat 20.)

But yes, this, all of this. No vaccine grants 100% immunity to 100% of recipients. All any vaccine can do is boost your resistance. You’re (probably) not immune to any disease you’ve been “immunized” against. You’re just (probably) more resistant than you otherwise would have been. This will vary from disease to disease, vaccine to vaccine, and person to person.

If the vaccine is effective enough and enough people get it, we can achieve practical immunity by making infection and transmission so difficult and unlikely that the wild virus dies out entirely. This has been accomplished with smallpox, and we’re thisclose to doing it with polio.

I think it comes down the the difference between Sterilizing Immunity and Essential Immunity.

The polio vaccine provides sterilizing immunity, meaning that once you’ve had the vaccine you can no longer get polio. You are 100% immune.

Covid vaccines all presently provide essential immunity. I pretty sure this has to do with COVID being a SARS (Severe acute respiratory syndrome) virus. ‘Essential’ means that you can still be infected with COVID and it can get a little bit of a hold on your upper respiratory system, but it’s unlikely to spread very far within you as your immune response will effectively defeat it before anything serious happens.

So, the Pfizer vaccine with it’s 95% effective immunity number what you get is that 95 out of hundred people who have gotten the vaccine and then are exposed sufficiently to the virus will get from what has been reported as asymptomatic infection to possibly some small immune response as their essentially immune bodies defeat the virus quickly. This is where the asymptomatic spreader thing we’ve heard about comes from. An essentially immune person with this exposure can infect someone else before their body defeats the virus. Truly asymptomatic people don’t even know they’re carrying a load of the virus.

The bodies of the other 5 people out of a hundred vaccinated with the Pfizer vaccine won’t successfully create the antibodies needed to be what is considered essentially immune. These folks if exposed to the COVID virus will not be able to fight it off. These are what has been reported as the Breakthrough cases of COVID infection that we’ve all heard about. Without hardly any exceptions, none of these breakthrough cases end up in the hospital as they still have much greater immunity than an unvaccinated person.

So, when you look at this big picture and then reassess mask wearing and physical distancing and washing hands and all those other things, I think you can see how important those things still are.

Vaccine hesitancy: I wish I could find and link a transcript but I can’t find it so I have to paraphrase. This morning I listened to some local (state level) government guy on the radio state something like this, ‘Of the 142 ICU beds available in these 13 rural counties almost all of them are currently filled with COVID patients, and every single one of them are unvaccinated people.’

This SARS spreads like many other viruses. Virus clinging to aerosoled spit particles, the hand to face thing after you touch a contaminated surface. All the stuff we’ve all known about since your mom taught you to cover your mouth when you cough when you were a kid.

The local health departments numbers in my county as of 4/30 state that 34% of all available hospital beds are filled with COVID cases. With all the other reasons people end up in the hospital this leaves only 16% of all hospital beds open.

Getting vaccinated makes it highly unlikely I’ll be taking one of those left over beds. How about you?

Should have added ‘as easily.’

I got vaccinated the moment it was available to me in late January (77 year old guy). I don’t need to be convinced of that. I just need to understand immunity and this thread is extremely helpful. Thank you all. Apropos of assessing risk, it would be very helpful to the efforts at reducing this disease, I think, if we could have some data on the percentage of people who die every day of Covid that have NOT been vaccinated. I presume virtually none of them have been. Are there data covering this question?

Good that you’re vaccinated. I got my second Pfizer shot on Feb 3rd. I mention it because so many still aren’t and they could have been and all they had to do was want to, and somehow still choose not to.

That guy I listened to on the radio this morning is the first time I’ve heard anyone speak of unvaccinated deaths from COVID. I haven’t really looked into finding numbers, but based on the info that essentially immune people don’t end up in the hospital and even the breakthrough cases don’t end up there I would guess that almost all the people dying from COVID from here on out will be unvaccinated people.

We don’t know the actual number of breakthrough cases as it is definitely underreported. If you were vaccinated, got COVID, had a mild cough or minor loss of taste, it might never find its way to the CDC. What we do know is that thousands of breakthrough cases have been documented, and approximately 9% of those thousands of cases have resulted in hospitalization. Breakthrough deaths are approximately 1.4% of total documented cases, or 15% of those who are hospitalized. It’s almost certain that all of these numbers are undercounts, as noted above, but the reality is that unless that undercount is many magnitudes in scope, your chances of dying once fully vaccinated are very slim.

Good cite!

Two good quotes (among others) from it:

an immune response doesn’t necessarily provide immunity

The common cold for example, the symptoms of a cold are classical immune responses, but you don’t acquire immunity.

Yes, that’s it exactly. It’s probably significantly higher but the cases are so mild they go barely noticed or are attributed to the flu.

Is the tetanus vaccine in that category? I assume so, as there are very few cases among the vaccinated, and it’s not the sort of thing that you can have “herd” immunity from.

You should be getting a tetanus booster shot every 10 years or so.