Jump to content

Will COVID be eliminated once everyone is vaccinated?


Alfred001
 Share

Recommended Posts

Once everyone has been vaccinated, is it to be expected that COVID will simply die off in lieu of any further hosts or will it be forever bouncing around like the flu, opportunistically infecting the odd unvaccinated person or the 5% of the vaccinated (as the vaccines are supposed to be 95% effective) whose defenses it manages to get past?

Link to comment
Share on other sites

1 minute ago, Alfred001 said:

Once everyone has been vaccinated, is it to be expected that COVID will simply die off in lieu of any further hosts or will it be forever bouncing around like the flu, opportunistically infecting the odd unvaccinated person or the 5% of the vaccinated (as the vaccines are supposed to be 95% effective) whose defenses it manages to get past?

In time, possibly. Smallpox for example has been eradicated...Polio also I think. 

Link to comment
Share on other sites

52 minutes ago, Alfred001 said:

Once everyone has been vaccinated, is it to be expected that COVID will simply die off in lieu of any further hosts or will it be forever bouncing around like the flu, opportunistically infecting the odd unvaccinated person or the 5% of the vaccinated (as the vaccines are supposed to be 95% effective) whose defenses it manages to get past?

Could be the latter if the rate of generation of new variants exceeds the ability of vaccines to keep up. We are years from vaccinating the whole population.

Link to comment
Share on other sites

Polio is still endemic in Afghanistand and Pakistan and I believe there have been irregular detections elsewhere.

To OP, at this point it is not clear. If vaccination was available early in the pandemic and/or if the infection levels where kept at a low level until now, and if everyone was getting vaccinated, then the answer would have been a yes.

However, one should take a step back in understanding how eradication works. It is not necessarily just a matter of vaccination, but it is about creating a situation where an infected person is unable to infect enough folks to sustain pathogen spread.

Herd immunity could be achieved by a combination of vaccination, immunity, as well as social measures (e.g. distancing) for example. 

But right now we have still over 14.8 million detected infections (and likely many more undetected) which is a huge reservoir for the virus and has a high risk of the creation of new variants. I have lost track of how many variants there are now in circulation, though only relatively few are classified to be of concern. Nonetheless, there is a big risk that for at least some of the variants, the vaccine will be less effective. We have already observed across the world that the UK variant (B.1.1.7) has displaced the wildtype. And this also affects how we should interpret vaccine efficacy data. Pfizer/BioNTech and Moderna efficacy data were generated earlier in the pandemic where mostly the wildtype was around. However, AstraZeneca already included data from patients with the B.1.351 (South African) strain, against which the vaccines might not work as well.

Some smaller data sets indicate for example that the Pfizer/BioNTech vaccine is about 89.5% effective against any infection with the B.1.1.7 variant and only 75% against B.1.351 in some groups (DOI: 10.1056/NEJMc2104974). However, they still protected with over 90% against severe diseases. The issue there is that while it prevents hospitalizations, it is still possible that folks get infected and may potentially transmit it to vulnerable persons.

Aside from variants we got the issue that in many (most) populations we will not achieve anything close 100% compliance. Surveys in various countries, including the US, UK and Canada, indicate that up to 35% of those surveyed indicated that they won't get the vaccine. Another big issue is worldwide-timing. If vaccines are only provided in richer countries, then those who cannot afford it are basically a reservoir for the virus. If we take another year to vaccinate them, it will be a full year where new variants can rise.

But even if just focus on local issues (and I want to emphasize that this would be really stupid to address a pandemic), we can do a little bit of a back-of-the-envelope calculation here. Let's focus on vaccination as the sole measure and let's assume we need ~80% immunity in the population to reach herd immunity.

Let us further assume that the vaccines have an effectiveness of 90%. In order to achieve 80% immunity, it would be necessary to vaccinate 89% of the population to reach the herd immunity target. Only few countries (according to polls) are at that level of theoretical compliance. If we use US polls as an estimate of vaccine willingness (~75%), we can estimate that with a 90% effective vaccine we will have ~68% immunity, lower than almost all current estimated requirement for herd immunity. 

If the vaccine effectiveness goes down to 80% (due to variants for example) we would need to vaccinate every single person. So even if there are no barriers to providing vaccines to folks, it is tricky to rely on it alone to push down viral numbers to a degree that there is no net transmission. 

So no, based on the current situation I actually do not think that the current rollout in practice is likely going to eradicate the virus completely. The more likely scenario (I believe) for now is that it will become endemic. However, the optimistic scenario is that it will be better controlled via regular vaccines (and treatments) and won't have the same horrible death toll in the future. It might indeed become something like a flu, which, I want to emphasize has regularly costed many lives and is not really harmless either (though compared to COVID-19 it is comparatively tame). 

And as a minor sidenote, I would like to emphasize how behavioral changes have affected flu-related deaths. In the years prior 20-50k folks are estimated to have died each year from influenza in the US. Last year  it was a few hundred reported so far.

Link to comment
Share on other sites

  • 2 weeks later...

Just to add to the issue of variants.  Even if vaccines are effective against the new variants, there is the issue that by now it is pretty clear that they have a higher transmissibility. B.1.1.7 has effectively replaced the wildtype and has up to 90% higher transmissibility. Based on preliminary studies B1.617.2 seems to be even higher (and in places is starting to replace B.1.1.7).

The reason why that is relevant is that a higher level of immunity within a population is required to deal with a higher transmissibility. A value to indicate the ability to spread is based on the basic reproduction number (R0) which is the average number of folks infected by a given infected person within a susceptible community. The effective reproduction number (Re) is then dependent on the susceptibility (s) of the population, taking e.g. immunity due to vaccination and other measures into account.

I.e. Re= s*R0.

In order for the disease to vanish, the effective reproduction number needs to go below 1. As the immunity in a population is given by 1-s we can then look for

1-s > 1-1/R0 to estimate how much immunity we need for that to happen. 

Originally the R0 for the wildtype SARS-CoV-2 was estimated to be around 2.5, which would require only 60% immunity in the population to stop. However estimates with larger data sets (and with the unknown impact of undetected spread) have put R0 quite a bit higher (3.6 and up), which would require over 72% immunity to achieve herd immunity, with estimates as high as 84%

Now if we increase R0 even higher for B.1.1.7 and B.1.617.2 we are approaching required immunity levels of 90%, which is basically impossible to achieve just by immunization.

 

Link to comment
Share on other sites

  • 6 months later...

So...here we are half a year later and I'm scheduled for a booster shot between Xmas and NewYear. After two Pfizer shots that I tolerated well, I was wondering whether to get that again or a Moderna booster. I chose Moderna despite slightly higher safety risks of Myocarditis or Pericarditis (I'm guessing driving to get vaccinated poses similar level of risk), mostly due to availability.

Moderna also seems to be considered more effective. Apparently Pfizer shots only have 30% of the mRNA load of the Moderna shots, so the Pfizer boosters are full doses where the Moderna boosters are half doses.

Related to that, for those without vaccine (and even those that have been), can the Omicron variant serve as a "vaccinator" (or booster)? Not that it would be recommended, but if it is a better "non-option" than say Delta, could it eventually be useful in that way?

Also, are the variants competing with each other? Can some strains crowd others out?

Link to comment
Share on other sites

32 minutes ago, J.C.MacSwell said:

for those without vaccine (and even those that have been), can the Omicron variant serve as a "vaccinator" (or booster)? Not that it would be recommended, but if it is a better "non-option" than say Delta, could it eventually be useful in that way?

I'll give you a definite "maybe" on that, but we do know that those who are unvaccinated but who have been infected with Delta variant seem to lack protection against the new Omicron variant, so it's not unthinkable that an Omicron infection will similarly fail to provide protection backwards (or forwards) to other strains.

Just because my chainmail vest protects me against swords doesn't mean it will protect me against daggers, or even other types of swords...

Link to comment
Share on other sites

2 hours ago, J.C.MacSwell said:

So...here we are half a year later and I'm scheduled for a booster shot between Xmas and NewYear. After two Pfizer shots that I tolerated well, I was wondering whether to get that again or a Moderna booster. I chose Moderna despite slightly higher safety risks of Myocarditis or Pericarditis (I'm guessing driving to get vaccinated poses similar level of risk), mostly due to availability.

Moderna also seems to be considered more effective. Apparently Pfizer shots only have 30% of the mRNA load of the Moderna shots, so the Pfizer boosters are full doses where the Moderna boosters are half doses.

Related to that, for those without vaccine (and even those that have been), can the Omicron variant serve as a "vaccinator" (or booster)? Not that it would be recommended, but if it is a better "non-option" than say Delta, could it eventually be useful in that way?

Also, are the variants competing with each other? Can some strains crowd others out?

There seems to be evidence that choosing a booster different from your previous shots widens your scope of protection. 

Omicron seems to be crowding out delta in the UK, at great speed. What I'm not clear about is whether this means delta will die out. I suppose that if omicron confers immunity against delta that would be expected: omicron would tend to get to a person first and then they would be less likely to catch delta later. But if omicron does not confer significant immunity against delta, I don't see why omicron's presence would stop delta proliferating as well.

Maybe someone more knowledgeable can comment.  

Link to comment
Share on other sites

4 hours ago, J.C.MacSwell said:

Related to that, for those without vaccine (and even those that have been), can the Omicron variant serve as a "vaccinator" (or booster)? Not that it would be recommended, but if it is a better "non-option" than say Delta, could it eventually be useful in that way?

I would be careful about that. We do not have good age-stratified data on unvaccinated severe cases yet (there is another report from SA which I should spend more time on, but from skimming it seems not to be conclusive yet, either). Current data suggests that it is not worse and there is at best a careful perhaps on whether it could be milder on average. Each individual might still face severe consequences, especially in the older age segment. Moreover, from a public health perspective, if the virus is less virulent, but spreads faster, it can still have a similar or higher net burden than the more virulent variant. In fact, spread is the more critical value here, since if it manages to spread through the population in a way delta still couldn't, we could actually face much higher net hospitalizations. This is exactly the scenario public health officials are very afraid of.

1 hour ago, exchemist said:

Omicron seems to be crowding out delta in the UK, at great speed. What I'm not clear about is whether this means delta will die out. I suppose that if omicron confers immunity against delta that would be expected: omicron would tend to get to a person first and then they would be less likely to catch delta later. But if omicron does not confer significant immunity against delta, I don't see why omicron's presence would stop delta proliferating as well.

There can be rather complicated situations pertaining to it. For example, folks can be co-infected with different variants (in areas with extremely high prevalence of infections), but only one manages to fully settle in its host. But for the most part the assumption is that infected persons regardless of the variant are less likely to immediately catch a related infection again. This is related to the amount of neutralizing antibodies, which are not highly specific and therefore should protect against most variations out there.

 

Link to comment
Share on other sites

  • 5 weeks later...

ok I am new here but would like someone to explain in terms I understand the meaning of the following portion of an article from the UK Health Security Covid Vaccine Surveillance Report Week 42

Seropositivity estimates for S antibody in blood donors are likely to be higher than would be expected in the general population and this probably reflects the fact that donors are more likely to be vaccinated. Seropositivity estimates for N antibody will underestimate the proportion of the population previously infected due to (i) blood donors are potentially less likely to be exposed to natural infection than age matched individuals in the general population (ii) waning of the N antibody response over time and (iii) recent observations from UK Health Security Agency (UKHSA) surveillance data that N antibody levels appear to be lower in individuals who acquire infection following 2 doses of vaccination

thanks in advance...

Link to comment
Share on other sites

8 hours ago, cazz said:

would like someone to explain in terms I understand the meaning of the following

People who have been vaccinated seem to have a stronger immune response to the virus and that response appears to last longer over time. People who got the virus without vaccine and gave a natural immunity (not due to vaccination) seem to have a weaker immune response overall and that response doesn’t last as long over time… the immunity seems to fade. People who donate blood are more likely to be vaccinated than the general population overall. When we see vaccinated people still getting infected, it seems related to their body having a weaker immune response than their fellow vaccinated peers. 

Edited by iNow
Link to comment
Share on other sites

5 hours ago, iNow said:

People who have been vaccinated seem to have a stronger immune response to the virus and that response appears to last longer over time. People who got the virus without vaccine and gave a natural immunity (not due to vaccination) seem to have a weaker immune response overall and that response doesn’t last as long over time… the immunity seems to fade. People who donate blood are more likely to be vaccinated than the general population overall. When we see vaccinated people still getting infected, it seems related to their body having a weaker immune response than their fellow vaccinated peers. 

I suspect they might be referring to some misinterpretations that have been circulating in social media apparently (I have not seen the posts, but have been made aware of them). Basically a pre-print found that vaccinated folks who got infected produced fewer antibodies targeting the N-protein of the virus.

In this context I think it is helpful if we get away from the notion of "strong" vs "weak" immune responses. The problem is that a "strong" response, can actually be harmful (cytokine storms are the most famous example). What we need is an "effective" response. I.e. a response that helps clearing the pathogen without or with minimal harm to the patient.

Going back to the results, current vaccines target the S-protein of the virus. In other words, once an infection is detected, the vaccine-primed immune system will predominantly mount responses to this target. If effective, the response to the N-protein is going to be weaker than in folks who are not vaccinated, because, well, they don't need it. The virus is predominantly cleared using the S-protein as target. 

I.e. phrasing it as either a strong or weak response can create a bit of a misunderstanding of how things actually work and how effective the overall response is going to be to avoid serious illness.

Link to comment
Share on other sites

8 hours ago, iNow said:

People who have been vaccinated seem to have a stronger immune response to the virus and that response appears to last longer over time. People who got the virus without vaccine and gave a natural immunity (not due to vaccination) seem to have a weaker immune response overall and that response doesn’t last as long over time… the immunity seems to fade. People who donate blood are more likely to be vaccinated than the general population overall. When we see vaccinated people still getting infected, it seems related to their body having a weaker immune response than their fellow vaccinated peers. 

I have donated 76 pints of my O rh positive blood over the years. Note though it is/was all donated. We don't get payed for it in Australia. ☺️

Edited by beecee
Link to comment
Share on other sites

On 1/15/2022 at 4:55 PM, iNow said:

I’m good with effective response. That was my intended meaning anyway 

No worries, it wasn't meant as criticism (and I assumed that is what you meant), but just trying to adjust language a bit as I learned that in public discussions folks get hung up on such concepts and that it can lead to severe misunderstanding of health messaging. But I also found that explaining these things does seem to help to mitigate spread of false or misleading information to some degree.  

In the spirit of OP one could probably add that with Omicron the even vague hope of herd immunity is even more shattered (if that was even possible). While some folks start claims regarding endemicity, it is important to point out that we are not even there yet. We are still very much in the outbreak phase and it is rather unclear when transmissions will drop to a level where we actually enter the endemic phase. Moreover, given the reservoir of infected people, the risk of new variants remain extremely high and given the spread (Omicron arrived almost everywhere in less than a month) creating an even more uncertain timeline.

This is a serious issue for health messaging, as folks demand some level of certainty about how things are going forward, but the current lack of clear answers drives folks to the crazy parts of the internet.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.