COVID Vaccination record vs. titer test result

[MoseyingAlong]

Have I completely missed this discussion?
If so, please tell me where it is.

Why are we exclusively focused on proof of COVID vaccination? Why not also accept a titer test result for those previously infected?

When I started nursing school, my yellow card record was lost (later found). So for a couple diseases, I got a titer test. The chickenpox was from having the disease, not the vaccination.

This seems like an obvious route to take. So I assume I'm missing some reason why it's not being discussed.

[PeteD01]

We do not yet know how to interpret antibody titers beyond that there has been an infection or vaccination or not as there is correlation between the degree of immunity and the titers of several antibodies but no clear understanding what a particular titer means in an individual in terms of immunity. Immunity against COVID-19 is complex and not simply a function of antibody titers.

However, and this is really important going forward and would simplify things tremendously:
Having a positive antibody test as evidence of previous infection regardless of the actual titer may be all that is required to predict high level immunity given that we have more and more evidence that immunity acquired through infection is highly protective; but we do not know how long it lasts.

[Abe]

Also there is evidence that prior covid infection has a shorter duration of efficacy than immunization for various immunology reasons not worth boring anyone with. This is in line with prior endemic coronavirus studies, so is not surprising in the least. Interestingly, the limited data on sars-cov-1 (the closest relative to this virus) suggests antibody titers remain elevated for years afterwards. That outbreak was controlled quickly so reinfection data was luckily not common. Yet the medium term (less than 6 months) reinfection rate for unvaccinated covid-19 patients is not negligible (0.5-1%). What’s most surprising is that a vaccine provides even medium-term efficacy, honestly. We are really lucky the vaccines panned out, even if they wane to some extent over a few months.

[tawyer]

Yes, you have missed it, from the CDC in August [1]

Two great answers already: the evidence suggests that the vaccine offers better immunity than an infection.

I agree that in some cases the titer test can be the way to go (possibly not with chickenpox, because the antibody titer can cost more than the vaccine administration). There was even a single study showing infection was better than vaccination for coronavirus [2], but that's all it was: a single study, now drowned out by the results of many studies.

[1] https://www.cdc.gov/media/releases/2021/s0806-vaccination-protection.html
[2] https://www.theatlantic.com/science/archive/2021/09/infection-immunity-covid-19-vaccines/620099/

[PeteD01]

This is a good summary of where we are currently in regards to immunity from previous COVID:

https://theconversation.com/covid-infections-may-give-more-potent-immunity-than-vaccines-but-that-doesnt-mean-you-should-try-to-catch-it-167122

[MoseyingAlong]

@PeteD01 @Abe @tawyer
Thanks for your replies, the info and the links to further resources.

Love how this community can provide help on so many different topics!

[BudgetSlasher]

In multiple setting I have seen proof of recovery from covid accepted in addition to proof of vaccination. The ones that come to mind quickest are dealing with international travel.

Usually that proof of recovery must be within a certain period of time ... 90 days seems to be the most common. I have seen one or two international entry requirements also putting a timeframe on vaccination.

[TrMama]

Antibodies are only one method our bodies use to fight disease. Long term immunity depends on T-cells, that cannot be measured via an antibody titre test. Therefore, just because someone has a low antibody titre, doesn't necessarily mean they have no immunity to a given disease.

In vivo (that's what happens in real bodies, not just in test tubes) there's lots of evidence that people who've been infected with Covid-19 can be reinfected. Sometimes multiple times. We don't yet know how long immunization lasts, but there's good evidence the two does regimen gives good protection for at least 6 months.

Immunization is also a much, much less risky way to gain immunity.