# What level of immunity does infection confer?



## Brendan Burgess (9 Jan 2021)

An interesting article in today's Irish Times which raised a question, I had wondered about.









						Covid vaccine could be conserved by excluding the already infected
					

People who have recovered from infection have already generated a protective immune response to the virus




					www.irishtimes.com
				




_A study on healthcare workers in Oxford, published last week in the New England Journal of Medicine, showed that only two workers out of 1,265 [ original article had a typo] that had previous confirmed SARS-CoV-2 infection became re-infected and both were asymptomatic, whereas there were 223 infections among 11,364 workers that had not previously been infected with SARS-CoV-2.

This study suggests that natural infection confers 100 per cent protection against Covid-19 disease and also gives very good protection against SARS-CoV-2 infection._



Brendan


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## Brendan Burgess (9 Jan 2021)

Here is the original paper



			https://www.nejm.org/doi/full/10.1056/NEJMoa2034545
		


*RESULTS*
A total of 12,541 health care workers participated and had anti-spike IgG measured; 11,364 were followed up after negative antibody results and 1265 after positive results, including 88 in whom seroconversion occurred during follow-up. A total of 223 anti-spike–seronegative health care workers had a positive PCR test (1.09 per 10,000 days at risk), 100 during screening while they were asymptomatic and 123 while symptomatic, whereas 2 anti-spike–seropositive health care workers had a positive PCR test (0.13 per 10,000 days at risk), and both workers were asymptomatic when tested (adjusted incidence rate ratio, 0.11; 95% confidence interval, 0.03 to 0.44; P=0.002). There were no symptomatic infections in workers with anti-spike antibodies. Rate ratios were similar when the anti-nucleocapsid IgG assay was used alone or in combination with the anti-spike IgG assay to determine baseline status.



*CONCLUSIONS*
The presence of anti-spike or anti-nucleocapsid IgG antibodies was associated with a substantially reduced risk of SARS-CoV-2 reinfection in the ensuing 6 months.


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## odyssey06 (9 Jan 2021)

I don't agree with the proposal in the original article. 
Aside from the points Brendan has raised to the effectiveness of the immunity...
We won't know how long immunity lasts... until it has expired and re-infections start occurring.
Our first spike in cases was last spring. To exclude such people from the vaccination cycle is reckless imo.

The article even includes these lines:
_It might be argued that we do not know if antibodies prevent re-infection with SARS-CoV-2 or if they persist for long periods after infection. However, the scientific evidence from the recent New England Journal of Medicine report and studies on other pathogens suggest that antibodies do protect against viral infections, and can persist *for months or years*._

How vague is that? A very doubtful basis on which the author wants to exclude people from potentially life saving vaccine programme on that basis.


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## Brendan Burgess (9 Jan 2021)

Hi Odyssey

The headline is misleading.

This is his proposal which I agree with

_An alternative approach is to prioritise vaccination for those who have not been infected with SARS-CoV-2, at least in the short term while vaccine supply is limited.  _

It's a question of priority. We know that you have no immunity as you do not have the antibodies. I have the antibodies, so I probably have some immunity. I am happy to wait for you to get the vaccine before I get it. 

This bit I was not sure about though: 

_Although mass serological testing of the population would be logistically challenging, it would allow identification of individuals who had asymptomatic infections, most of whom are known to develop antibodies. Although less clear cut than the confirmed PCR-positive cases, it might allow exclusion of another cohort from later rounds of vaccination. _

We have limited staff and the first priority should be to vaccinate as many people as possible. The next priority should be to treat sick people. 

Then if have medical staff sitting around with nothing to do because they have no vaccine to administer, they could start testing people for anti-bodies.

But practically, just exclude for the moment, those who have already tested positive or who have the antibodies.

Brendan


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## odyssey06 (9 Jan 2021)

Whatever about assigning of priority *within *a priority group nobody should be getting bumped down the priority groups just because they tested positive at a point in time e.g. last spring.
There is no scientific evidence to justify such a decision.
Language like "_Months or years_" and "_ most of whom are known to develop antibodies_" just doesn't cut it as scientific evidence of the level to justify such a decision.
Nobody would accept such level of 'evidence' e.g. in a vaccine trial.

And think of the mechanics of it. Surely it makes more sense to vaccinate the vulnerable in a specific site in one go e.g. an entire nursing home than to do it in two rounds.


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## odyssey06 (9 Jan 2021)

To add... I think when it comes to vaccinations within large priority groups in the general population e.g. 65-70 year olds, then optimally you would prioritise those without antibodies.


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## Brendan Burgess (9 Jan 2021)

Hi Odyssey

It really depends on what the limiting factor is.  

If there is no shortage of vaccines, then it doesn't matter as much.

But if there is a shortage and someone who doesn't need it gets it, then they are depriving or delaying someone else from getting it.

Interesting point about the "within groups" argument.  I am not sure. If they go to a nursing home where half  of the people have had the virus, then they should just vaccinate the other half first.   They can do the rest at some other stage. 

But if they are inviting individuals into a vaccination centre, those of us who have the antibodies, should ask for it to be deferred to a lower priority. I don't see any major logistical difficulty with that.  And if we have to apply for it, we should not apply for it until everyone else is done.

Brendan


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## Paul O Mahoney (10 Jan 2021)

Two studies find that COVID-19 antibodies last 8 months
					






					www.cidrap.umn.edu
				




The above is more evidence that immunity is gained after being infected.

On the point of deferral of giving vaccines to those with natural immunity, I think it would be a better idea to vaccinate those who have the antibodies and see if there is any change in the amount of antibodies present. (as a study)

Having that data would then be used to make the decision of deferral for others,  for example if no increase was gained by vaccinating maybe deferral would be an option for some.

Of course there is also evidence that people can become re-infected .


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## Paul O Mahoney (10 Jan 2021)

Slightly off topic Nature.com has a bibliography of studies on all aspects of covid studies that have happened.


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## Brendan Burgess (10 Jan 2021)

Paul O Mahoney said:


> I think it would be a better idea to vaccinate those who have the antibodies and see if there is any change in the amount of antibodies present. (as a study)



I imagine that someone is conducting that research.   

But they might be too busy vaccinating. 

Brendan


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## Purple (11 Jan 2021)

> _Although mass serological testing of the population would be logistically challenging, it would allow identification of individuals who had asymptomatic infections, most of whom are known to develop antibodies._


I don't see the logic of this. Serological testing requires the drawing of blood and sending that sample to a lab for testing. It is a more resource hungry process than just vaccinating people. I strongly suspect that we'll have access to enough vaccines before we have the infrastructure in place to distribute it.


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## Brendan Burgess (11 Jan 2021)

Pfizer-BioNTech COVID-19 Vaccine Frequently Asked Questions
					

Frequently asked questions on the emergency use authorization of the Pfizer-BioNTech COVID-19 Vaccine




					www.fda.gov


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## Paul O Mahoney (11 Jan 2021)

Purple said:


> I don't see the logic of this. Serological testing requires the drawing of blood and sending that sample to a lab for testing. It is a more resource hungry process than just vaccinating people. I strongly suspect that we'll have access to enough vaccines before we have the infrastructure in place to distribute it.


Personally I think the only way we are ever going to fully understand this virus and its medium to long-term effects on individuals is going to be by blood samples.
Equally the vaccines will need to be evaluation and again bloods would probably be the best way to get accurate data.

I appreciate that now is a time where we must again contain the spread of the virus and all resources must be pitted against the spread, including vaccine rollout. 

There are many in the science/medical world thinking that we may be battling covid for years to come so we need to fully understand what every treatment does and what they don't do, and whatever achieves that needs to be considered, no matter how ludicrous it may seem now.


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## Purple (11 Jan 2021)

Paul O Mahoney said:


> Personally I think the only way we are ever going to fully understand this virus and its medium to long-term effects on individuals is going to be by blood samples.
> Equally the vaccines will need to be evaluation and again bloods would probably be the best way to get accurate data.
> 
> I appreciate that now is a time where we must again contain the spread of the virus and all resources must be pitted against the spread, including vaccine rollout.
> ...


I agree but in the context of freeing up resources for a vaccination program it doesn't make sense.


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