To determine whether someone who has had COVID-19 has developed immunity to the SARS CoV-2 virus was one of the objectives of the innovation rapid response project CoviproteHCt. The mission of the research project was to “Identify protective immunity to SARS-CoV-2 in Health Care Personnel”. Being able to identify individuals with immunity would allow healthcare providers to appoint protected healthcare personnel to work in environments where the risk of exposure to the virus is heightened, such as intensive care units with COVID-19 patients.
A follow-up-study, SEROCOV, that was published by nature communications in August 2021, suggests, that the levels of IgG antibodies against SARS-CoV-2 Spike protein remain stable, or even increase, seven months after infection. Furthermore, pre-existing antibodies to common cold coronaviruses may be protective against COVID-19, according to the study.
Investigating Immunity in healthcare workers
The team’s objective was to gain a better understanding of the dynamics and duration of immunity to SARS-CoV-2 and to determine the impact of pre-existing antibodies against the coronaviruses that cause common colds. The scientists followed a cohort of healthcare workers at the Hospital Clinic for seven months after the start of the pandemic, observing the levels of antibodies against different SARS-CoV-2 antigens over time. According to ISGlobal researcher Carlota Dobaño, who led the research “This is the first study that evaluates antibodies to such a large panel of SARS-CoV-2 antibodies over 7 months”.
At four different timepoints between March and October 2020, the researchers took blood samples from 578 volunteering healthcare workers. Measured was the level and type of IgA, IgM or IgG antibodies to 6 different SARS-CoV-2 antigens. On top of that, the team also observed the presence of antibodies against the four coronaviruses that cause common colds in humans, as well as the neutralising activity of antibodies.
The analysis showed a level of IgG antibodies, that remained stable over the 7-month-period, with the exception of IgM and IgG antibodies against the nucleocapsid (N). These findings confirm results from other recent studies. “Rather surprisingly, we even saw an increase of IgG anti-Spike antibodies in 75% of the participants from month five onwards, without any evidence of re-exposure to the virus,” says Gemma Moncunill, senior co-author of the study.
Different HCoV-levels might explain variety in susceptibility
The results also suggest that antibodies to human cold coronavirus (HCoV) may have a reciprocal positive effect against COVID-19 infection or disease. This is supported by the fact that people infected with SARS-CoV-2 showed to have a lower level of HCoV antibodies. Symptom severity also appeared to be related to the levels of anti-HCoV IgG and IgA, with asymptomatic individuals showing higher levels than those with symptomatic infections. “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,” says Dobaño.
The SEROCOV-study was coordinated by the Barcelona Institute for Global Health (ISGlobal), an institution supported by “la Caixa” Foundation, in collaboration with the Hospital Clinic of Barcelona. CoviproteHCt was conducted by