Individuals who have had a SARS-CoV-2 infection prior to vaccination show strong immune responses, referred to as “hybrid immunity”, after vaccination. Results from the longitudinal COMMUNITY study, which is part of the National SciLifeLab-KAW COVID-19 Research program, show that this hybrid immunity persists over time – seven months – after vaccination.

The findings are published in a pre-print by the group of COMMUNITY researchers from SciLifeLab, Danderyd Hospital, Karolinska Institutet, Uppsala University, Public Health Agency of Sweden and KTH Royal Institute of Technology.

The COMMUNITY study is a longitudinal study that aims to examine the immune system over time after SARS-CoV-2 infection and vaccination. The cohort consists of 2149 employees at Danderyd Hospital and 118 COVID-19 patients. Study participants have been serologically tested every four months since April 2020. The most recent sampling of the entire cohort was in September 2021, and the next sampling is planned for January 2022. T-cell analyses and PCR screening studies are also ongoing.

It has previously been shown that SARS-CoV-2 infection before vaccination gives a very strong immune response, which is called hybrid immunity. Recent data published in the COMMUNITY pre-print show that this hybrid immunity persists over time (seven months) after vaccination.

Most of the study participants are now vaccinated with either Pfizer’s mRNA vaccine or Astra Zeneca’s adenovirus vector vaccine. “The study shows that neutralizing antibody levels decrease rapidly after vaccination for individuals who have not had a COVID-19 infection before vaccination. But neutralizing capacity against ten SARS-CoV-2 variants, including Delta, were more than two-fold higher in individuals who have had a SARS-CoV-2 infection prior to vaccination. This speaks in favor of booster vaccinations, especially to risk groups and those who have not been infected with SARS-CoV-2” says Charlotte Thålin, KI/SciLifeLab. The importance of hybrid immunity in vaccine policy is discussed in a New York Times article published by the group late October.

The COMMUNITY project is financed by The National SciLifeLab-KAW COVID-19 Research through funding from Knut and Alice Wallenberg Foundation.

Read the full pre-print and more about the COMMUNITY study.