Viral dynamics of SARS-CoV-2 variants in vaccinated and unvaccinated individuals

https://www.medrxiv.org/content/10.1101/2021.02.16.21251535v3

by walterbell • 5 years ago

64 20 5 years ago

medrxiv.org

LurkingPenguin2• 5 years ago

Acute infections in vaccinated and unvaccinated people feature similar proliferation and peak Ct...

If this is the case, what is the "long COVID" risk to people who experience breakthrough infections?

sudosysgen• 5 years ago

Lesser. They do say that vaccinated individuals clear the infection more quickly, and indeed cellular immunity takes some time to kick in. From that a good guess is that long covid risk is lower.

Also, remember that selection bias still exists. There are going to be individuals with replication but lower viral loads that never get tested because they have no symptoms, and there will likely be a higher proportion of those in the vaccinated group.

LurkingPenguin2• 5 years ago

I suspect that long COVID risk is lower in vaccinated individuals (and hope so as an expat who traveled halfway around the world to get vaccinated) but the risk should be quantified.

There are a growing number of reports of people with breakthrough infections who are experiencing symptoms that aren't "mild", and some reports of people with "long COVID" like symptoms. It's not reason enough to panic, but it's concerning, especially in light of the fact that until very recently, health experts and the media kept telling us that breakthrough infections were "rare" even as it was becoming evident they weren't.

tehjoker• 5 years ago

Hmm, this conflicts with other information out there that says Delta is 1000x peak load. Any insight into why that might be?

mdp20212• 5 years ago

I think that piece of information (1000x) was superseded many weeks ago, and was replaced with a more "linear" 3x.

That correction surely happened, but I have no idea if there were further updates, refinements, divergent estimates etc.

mdp20212• 5 years ago

...And in fact, it is now reported that the viral load for that variant is 300x, according to a study from South Korea.

criticaltinker3• 5 years ago

The biggest flaw with this study is that it does not account for prior natural infection. It has been thoroughly demonstrated that individuals who acquire immunity through natural infection have a robust and durable immune response [1][2][3]. Recent vaccination on top of this immunity is likely to further prime and improve immune responses to subsequent infection [4][5].

Not accounting for this fact is a significant confounding factor in the study, and I'm disappointed the authors made no distinction between unvaccinated and immunologically naive. This is a distinction that every sensible scientific discussion needs to acknowledge.

EDIT: please leave a comment down voters, I’m starting to think there’s some sort of targeted campaign against this type of information

Vaccine breakthrough infections exhibited similar proliferation dynamics as infections in unvaccinated individuals (mean peak Ct: 20.5, 95% credible interval [19.0, 21.0] vs. 20.7 [19.8, 20.2], and mean proliferation time 3.2 days[2.5, 4.0] vs. 3.5 days [3.0, 4.0]); however, vaccinated individuals exhibited faster clearance (mean clearance time: 5.5 days [4.6, 6.6] vs. 7.5 days [6.8, 8.2]).
If the Ct values in vaccinated and unvaccinated infected individuals reflect the same amounts of infectious virus, then this implies that individuals with breakthrough infections may be as infectious as unvaccinated individuals in the early stage of the infection, but remain infectious for a shorter time, reducing the total degree of onward transmission. These findings are in keeping with the hypothesis that vaccination protects against the severe manifestations of disease but offers less protection against infection in the upper airway. Precautions are therefore necessary to prevent onward transmission even from vaccinated individuals.

[1] Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells https://www.cell.com/cell-reports-medicine/fulltext/S2666-37...

[2] SARS-CoV-2 infection rates of antibody-positive compared with antibody-negative health-care workers in England: a large, multicentre, prospective cohort study (SIREN) https://pubmed.ncbi.nlm.nih.gov/33844963/

[3] Association of SARS-CoV-2 Seropositive Antibody Test With Risk of Future Infection https://jamanetwork.com/journals/jamainternalmedicine/fullar...

[4] Naturally enhanced neutralizing breadth against SARS-CoV-2 one year after infection https://www.nature.com/articles/s41586-021-03696-9

[5] Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine https://www.nature.com/articles/s41591-021-01316-7

walterbell2• 5 years ago

authors made no distinction between unvaccinated and immunologically naive. This is a distinction that every sensible scientific discussion needs to acknowledge.

Ideally, everyone would be tested for antibodies before receiving a vaccine, then we would have data to differentiate naive+vaccine from survivor+vaccine. This would be helpful for both science and public policy.

CDC needs to stop labelling people who are 13 days after their 2nd vaccine dose as "unvaccinated". A more accurate label would be "partly vaccinated".

criticaltinker3• 5 years ago

Ideally, everyone would be tested for antibodies before receiving a vaccine

I agree that would help make optimal decisions with regards to distributing a limited supply of vaccine doses.

However it's worth noting that even when antibodies drop below levels detectable by standard tests, individuals are likely to retain robust immune responses that provide sufficient protection from severe outcomes [1][2].

[1] SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans https://www.nature.com/articles/s41586-021-03647-4.pdf

[2] Prior COVID-19 protects against reinfection, even in the absence of detectable antibodies https://www.journalofinfection.com/article/S0163-4453(21)002...

thebruce87m3• 5 years ago

It might be that you alluded to the term “natural immunity” which now comes with extra baggage.

There seems to be a recent talking point for “natural immunity”, and two of my [uk based!] friends who seem to end up on the wrong side of every issue are parroting this. They are somehow both tuned in to US YouTube talking heads, Tucker etc despite being in the UK.

The message that is being pushed as I understand it is “let the virus rip” since if(!) you come through unscathed you will end up with better immunity? Maybe I misunderstand it but they both in a “anti covid vaxx” stance so I think that’s their reasoning - it is somehow better to take your chances with the virus than get the vaccine.

Note that they are both engineers.

cies• 5 years ago

it is somehow better to take your chances with the virus than get the vaccine.

As i understand it that statement is more true when the age (and presence of comorbidities) of the subject goes down.

<10y: why on earth would we vaccinate these people?

70y: why on earth not?

Many of us are in the middle, and that means things are not that clear cut. I believe everyone should choose for themselves, as herd-immunity is off the table and outbreaks amoung the young do not cause much strain on the health care system.

Jeema101• 5 years ago

You could try the 'scared straight' approach and direct them to this thread on the /r/nursing subreddit about what other ICU nurses are seeing right now regarding unvaccinated Covid patients in the ICUs:

https://www.reddit.com/r/nursing/comments/pbvcdu/uhh_are_any...

Some interesting quotes that stood out to me:

"They’re dropping like flies in our ICU. 20- and 30-year-olds on vent and 99% of them unvaccinated."

"There are really only 2 options we are seeing for patients here. -you die -you become permanently disabled. And they are sent to Rehab or Long Term Care"

"Dialysis here. All my new patients in the past six months have had their kidneys damaged due to covid. All of them."

Viral dynamics of SARS-CoV-2 variants in vaccinated and unvaccinated individuals

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