Human antibodies produced to fight the virus that causes Covid-19 remain stable and may even increase seven months after infection, a new study suggests.
Researchers from Barcelona Institute for Global Health (ISGlobal) conducted a review on the duration of immunity to SARS-CoV-2 and the role of pre-existing antibodies against similar coronaviruses that cause common colds.
They examined blood samples from 578 healthcare workers taken at four intervals between March and October 2020 that showed a robust response to the SARS-CoV-2 spike protein.
The results, published in Nature Communications, support the theory that pre-existing antibodies against common cold coronaviruses could protect people against Covid-19.
Researcher Dr Carlota Dobano and her team followed a cohort of healthcare workers at Barcelona Hospital Clinic from the beginning of the pandemic, to evaluate the levels of IgG antibodies against different Covid-19 antigens over time.
“This is the first study that evaluates antibodies to such a large panel of SARS-CoV-2 antibodies over seven months,” she said.
Dr Gemma Moncunill, a co-author of the study, said: “Rather surprisingly, we even saw an increase of IgG anti-spike antibodies in 75 per cent of the participants from month five onwards, without any evidence of re-exposure to the virus.”
Results also suggested antibodies against human cold coronaviruses (HCoV) could confer cross-protection against Covid-19 infection or disease.
The authors also discovered that people infected by SARS-CoV-2 had lower levels of HCoV antibodies, and that the level of antibodies was higher in asymptomatic carriers than in those with symptoms.
“Although cross-protection by pre-existing immunity to common-cold coronaviruses remains to be confirmed, this could help explain the big differences in susceptibility to the disease within the population,” Dr Dobano said.