96% retain protective antibodies against COVID-19 nine months after infection

96 percent of those infected with COVID-19 retain protective antibodies for at least nine months after confirmed infection. This is shown by a large study from Danderyd Hospital and Karolinska Institutet using antibody tests developed by researchers at KTH and the SciLifeLab Autoimmunity And Serology Profiling unit, among them, Peter Nilsson (SciLifeLab/KTH).

In the spring of 2020, the COMMUNITY-study was launched as a way to form a better understanding of how our immune-system responds to Covid-19. Samples were collected from 2149 employees at Danderyd Hospital (DH) – and today, nearly one year has passed and the third phase of the study is now completed.

The encouraging results show that 96 percent of those with antibodies in the spring of 2020 still had measurable levels of antibodies against the COVID-19 spike protein nine months later. Furthermore, two-thirds of them also had measurable levels of SARS CoV-2 specific T-cell memory. 

Weekly screenings also showed that less than one percent of the participants with antibodies became infected again during a period of ten weeks.

“By examining several components of the immune system nine months after the review infection, we can see that even mild symptoms provide a long-lasting and broad immune system. One concern has been whether an individual with antibodies can carry the virus and carry the infection without showing any symptoms themselves or not, but the risk seems to be very small”, says Charlotte Thålin, responsible researcher for the COMMUNITY-study (DH, KI).

Researchers have now established that the antibodies seem to work better than expected.

“In the study, we measured both antibodies and T-cell memory in all 1,884 study participants. In addition to the fact that 40 percent of the entire group has now had COVID-19, we also see that less than two percent of those without antibodies have evidence of SARS-CoV-2 specific T-cell memory, which suggests that antibodies to the spike protein reflect the general immunity”, says Sebastian Havervall (DH, KI).

The COMMUNITY-study continues

“Now the COMMUNITY-study continues and the next sampling will take place in May when a large proportion of the participants is expected to have been vaccinated. This will allow us to compare the immune system after natural infection with that after vaccination”, says Charlotte Thålin.

The antibody test has been developed by Sophia Hober (KTH) and Peter Nilsson (KTH) at SciLifeLab and KTH, and The specific T-cell response on SARS-CoV-2 was analyzed with a test developed by SciLifeLab researcher Sara Mangsbo (UU) and her team, in collaboration with Pierre Dönnes, CEO SciCross AB. SciLifeLab researcher Mia Phillipson (UU) has also been involved in the study.

SciLifeLab news have been reporting on the study since it began in May 2020:

Danderyd Hospital staff will be tested for COVID-19 antibodies
First phase of the Danderyd Hospital’s COVID-19 study complete
Four out of five still have antibodies against SARS-CoV-2

Photo: Cecilia Larsson Lantz


Last updated: 2021-02-18

Content Responsible: David Gotthold(