COVID-19 vaccination provides 60% to 94% protection against reinfection

Individuals previously infected with SARS-CoV-2, the virus that causes COVID-19, still benefit from vaccination, gaining 60% to 94% protection against reinfection, depending on the variant. A new study led by Katrine Finderup Nielsen at Statens Serum Institut, Denmark, reports these findings November 22nd in the open access journal PLOS Medicine.

During the recent pandemic, vaccination has been one of the best tools available for curbing the spread of COVID-19. People infected with the virus are known to develop long-lasting natural immunity, but Finderup Nielsen and her team wanted to know whether these individuals would still benefit from receiving the vaccine. The team analyzed infection and vaccination data from nationwide Danish registers that included all people living in Denmark who tested positive for the virus or were vaccinated between January 2020 and January 2022. The data set included more than 200,000 people who tested positive for SARS-CoV-2 during each of the Alpha, Delta and Omicron waves. Their analysis showed that for people with previous infections, vaccination offered up to 71% protection against reinfection during the Alpha period, 94% during the Delta period and 60% during the Omicron period, with protection lasting up to nine months.

These findings show vaccination protected people against SARS-CoV-2, over and above the protection offered by natural immunity during all three waves of variants. The authors point out that the current study was too short to determine whether the vaccine protects against severe outcomes, such as death and hospitalization, and that future studies with longer follow-up times will be necessary to answer this question. From a public health perspective, these insight into vaccine effectiveness can help decision makers plan the timing and execution of vaccination strategies to make them most effective.

In our study we find a significant vaccine effectiveness against SARS-CoV-2 reinfection, and this shows the importance of vaccination also for those who might be protected by natural immunity."

Katrine Finderup Nielsen at Statens Serum Institut, Denmark

Journal reference:

Nielsen, K.F., et al. (2022) Vaccine effectiveness against SARS-CoV-2 reinfection during periods of Alpha, Delta, or Omicron dominance: A Danish nationwide study. PLOS Medicine.


  1. Eugene melnyck Eugene melnyck Canada says:

    What proof is there?

  2. Brandon W Brandon W United States says:

    This vaccine was only ever about 12% effective against COVID for the first week then 1% effective after that. So how, all of a sudden, the vaccine is "94% effective" now. Like they claimed in the past about the vaccine. It's like people are so stupid they don't remember shit that happened a year ago, 8 months ago, and so on.
      Don't put this poison in your body. If you've already had COVID you're 13x more protected than the vaccine.

  3. Andre Burnens Andre Burnens Switzerland says:

    Contradicts common sense and wealth of data. But I will have a look at the data.

  4. brian kofke brian kofke United States says:

    So how did the study differentiate acquired immunity over vaccine immunity when all the participants had acquired immunity before vaccination? I bet the author is bought and paid for by phizer. Shameful.

  5. joel schluter joel schluter Canada says:

    This just proves they are still testing and know nothing about this “vaccine”.

  6. Gord Lindsay Gord Lindsay Canada says:

    In Ontario, Canada, the incidence of hospitalization has always been higher among the vaccinated.  But, sadly, your study did not cover hospitalization.

  7. Angela Anderson Angela Anderson Canada says:

    Funny, I know people vaxxed that have gotten covid ateast twice after vaxx, one girl got it 3 times. I've never had it and never had the shot. I work in a school where it was rampant. I'll take a hard pass!

  8. Mark Lewis Mark Lewis Spain says:

    The VE peak being 14 to 43 days after vaccination sounds a lot of some sort of an artifact of not getting tested as people believed being safe from reinfections so soon after the vaccination. Was it even possible to get a test if you admit being recently fully vaxxed?

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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