COVID-19 reinfections rare but possible – healing practice

Those who have recovered can still transmit SARS-CoV-2

The risk that people who have already survived a SARS-CoV-2 infection will be infected again is very low, but it does exist. In addition, those who have recovered may still be able to infect other people. This emerges from a British study in which employees of the English health system were monitored.

The so-called SIREN study (Sarscov2 Immunity & REinfection EvaluatioN), which was commissioned by the English health authorities NHS, is to find out whether a previous infection with the coronavirus SARS-CoV-2 protects against future infection with the same virus. The first results from this research work are now available on the medical preprint server “medRxiv” released.

At least five months of immunity after SARS-CoV-2 infection

According to the study, previous infections with the coronavirus SARS-CoV-2 (trigger of COVID-19) offer a certain immunity from re-infection, but those who have recovered can still carry the virus in themselves and infect others. Scientists from the UK health authority Public Health England (PHE) recently found that immunity lasts for at least five months after surviving SARS-CoV-2 infection, but recovery can still pass the virus on to others.

Course of the study

As of June 2020, PHE researchers have tested over 20,000 healthcare workers across the UK for COVID-19, as well as for the presence of antibodies that suggest people have already been infected. For this purpose, 129,189 PCR tests and 91,165 antibody tests with blood samples were carried out.

6,614 participants reacted positively to the coronavirus antibody test. Between June 18 and November 24, 2020, the researchers in this group discovered 44 potential SARS-CoV-2 reinfections. In 15 of these cases, symptoms of the disease reappeared.

44 potential reinfections

The research team rated two of the reinfections as very likely. The virus was detected in both cases by additional tests. The remaining 42 reinfections were classified as “possible”. In these cases, there were more than 90 days between two positive PCR smears or positive PCR tests were performed even though antibodies against SARS-CoV-2 were present.

What is the risk of reinfection?

Converted to the risk, this would mean, according to the study, that a first infection reduces the risk of a further infection within five months by 83 percent if all 44 cases are actual reinfections. If it turns out that only two of the cases are actual reinfections, the risk reduction would be 99 percent. For comparison: the vaccines currently available offer a reduction in the risk of infection of around 95 percent.

At least 83 percent protection against reinfection

The working group comes to the conclusion that naturally acquired immunity as a result of a SARS-CoV-2 infection is associated with at least 83 percent protection against recurrence. This protection seems to last for at least five months. There are currently no studies beyond this period.

Even those who have recovered seem to be able to transmit the virus

However, the PHE researchers warn that while the available study results suggest that people with SARS-CoV-2 antibodies rarely get the disease again, some of these people still carried high amounts of the virus. This is an indication that you can continue to transmit the virus, although you no longer get sick yourself.

Clear picture with question mark

“This study has given us the clearest picture yet of the nature of antibody protection against COVID-19, but it is crucial that people do not misunderstand these early results,” said Professor Susan Hopkins, who led the study.

It is now known that most people who have become infected with the virus have formed antibodies and are initially protected against re-infection, but it is still unknown how long the protection lasts and how high the risk is that it will Group of people passing the virus on. The head of the study therefore emphasizes that those who have already gone through COVID-19 should adhere to the safety rules in order to protect others.

What’s next?

The team reports that participants will be followed up for another 12 months to see how long any immunity will last. The aim is also to monitor how long immunity acquired through vaccines lasts and whether vaccinated people are able to transmit the virus to others. (vb)

Author and source information

This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical professionals.


Diploma-Editor (FH) Volker Blasek


  • Deutsches Ärzteblatt: SARS-CoV-2: Reinfections in medical staff still rare (published: January 18, 2021),
  • Portal of the SIREN study (accessed: January 19, 2021),
  • PHE: Past COVID-19 infection provides some immunity but people may still carry and transmit virus (veröffentlicht: 14.01.2021),
  • V. Hall, S. Foulkes, A. Charlett, et al.: Do antibody positive healthcare workers have lower SARS-CoV-2 infection rates than antibody negative healthcare workers? Large multi-centre prospective cohort study (the SIREN study), England: June to November 2020; in: medRxiv, 2021,

Important NOTE:
This article is for general guidance only and is not intended to be used for self-diagnosis or self-treatment. He can not substitute a visit at the doctor.


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