I recently read in the news that countries are thinking to offer a "green passport" based on the vaccination against SARS-CoV-2, allowing vaccinated people to do things with less restrictions than the non-vaccinated :

New York Times

BBC News



If those passports are to be put in place, why do they not include people that were exposed naturally to SARS-CoV-2, this number being bigger days after days (60 millions people, 17/02/2021) ?

Does that mean that vaccines offer more immunity than being exposed naturally to SARS-CoV-2 and recover ?

My questions don't address the ethical aspect of implementing a "green passport", I'm only trying to figure out if vaccination offers more immunity than being exposed to the virus. A possible answer to this question can simply be "we don't know so far" because of the lack of feedback on a long term view.

  • $\begingroup$ The vaccine will protect you from severe disease, hospital stays and death. Isn't that enough? $\endgroup$
    – Chris
    Feb 17, 2021 at 13:49
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    $\begingroup$ Placebo-controlled trials are the gold-standard of evidence for something like this, but that's not really a possibility for assessment of immunity in previously infected individuals. Instead you'd need something like a prospective observational cohort study, which would need massive enrollment efforts and would likely still fall short of the strength of evidence provided by vaccine trials. My guess is that's why regulators are hesitant to make strong inferential claims about the strength of immunity after infection. $\endgroup$
    – MikeyC
    Feb 17, 2021 at 16:45
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    $\begingroup$ Perhaps the reason has nothing to do with the quality of the immunity, but is simply down to the fact that immunization can be well-documented, while having had the virus (especially a mild case that didn't require hospitalization) is not. There's also the practical aspect that it would encourage more people to be vaccinated. $\endgroup$
    – jamesqf
    Feb 17, 2021 at 18:10
  • 1
    $\begingroup$ @Chris Yes of course I don't reject the usefulness of the vaccines, but it is another topic. My question is more focused on the immunity acquired by catching the virus compared to the immunity acquired by a vaccine. $\endgroup$
    – Genorme
    Feb 18, 2021 at 7:38
  • $\begingroup$ @jamesqf Exactly, the immunity acquired by a vaccine is subjected to trials so it is certainly more documented than natural occurences. $\endgroup$
    – Genorme
    Feb 18, 2021 at 7:49

2 Answers 2


As @MikeyC and @jamesqf pointed in the comments, vaccines are better documented than the actual cases, whereas qualifying the immunity conferred by having recovered from Covid-19 would require large cohort studies.

However, one can follow up thir argument in many ways:

  • It would be reallys urprizing, if large-scale cohort studies have not been udnerway or already available by now: while nationwide testing may still be lacking in many countries, masive and repeated testing campaigns in specific regions are not a rarity by now. (see, e.g., here and here)
  • Hospitalization is not a necessary requirement for attesting a covid case - one could test unvaccinated persons for the presence of the Covid-specific antibodies.
  • There is much still unknown about the vaccines themselves - particularly about whether the immunity conferred is a lasting one, and whether.
  • Moreover, the fact that many people might have lived light cases of Covid does not make it easier for attesting the efficacy of the vaccines. Public authorities openly warn that the vaccine might be inefficient and a vaccinated person might be still a carrier of the disease.

In other words, "we don't know" is the most likely answer.

As the OP, I forgo the ethical issues raised by the "green passport" - these are not only those related to the restrictions on the individual freedom, but also the discrimination against the individuals to whom the vaccine is counter-indicated (e.g., allergics, pregnant women, people with weakened immunity, etc.)


It is said vaccines are over 90% effective. But I think natural obtained antibodies from Covid-19 and recovery offer more immunity than vaccines. The problem is that no pne can be sure to survive the infection.

  • $\begingroup$ I understand your opinion but it is not based on evidences, I am looking for a formal proof (if any up to date) that can confirm or infirm that immunity acquired by a vaccine is better. $\endgroup$
    – Genorme
    Feb 18, 2021 at 9:44
  • $\begingroup$ We welcome new contributors to SE Biology, but ask that they read the Tour and the Help on answering questions. As the poster says, you are not providing an answer but an opinion unsupported by evidence, which makes your answer unsatisfactory for this question and answer site. $\endgroup$
    – David
    Feb 18, 2021 at 16:45

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