Antibodies to the SARS-CoV-2 virus, which causes covid, are maintained for at least 20 months after suffering the disease, As demonstrated by a study conducted with a 20-month follow-up on 247 healthcare workers in Catalonia who were infected with covid at the beginning of the pandemic.
The study, co-led by Barcelona Institute for Global Health (ISGlobal), Catalan Health Institute (ICS) and IDIAP Jordi Gol (IDIAP JG), with the collaboration of the Daniel Bravo Andreu Private Foundation (FPDBA), also showed this obesity, age, and being a smoker are associated with a lower antibody response.
The research, the results of which are published this Thursday in the journal BMC Medicine, wanted to know how long the immune response lasts after SARS-CoV-2 infection.
In a recent study with a cohort of the Catalan population aged 40 to 70, ISGlobal researchers led by Carlota Dobaño showed that one in three unvaccinated people no longer had detectable antibodies one year after infection.
“However, it is important to conduct this type of study in several cohorts. The cohort of health professionals described here includes younger and more virus-exposed people, who have had a symptomatic infection and in whom we have been able to take regular samples in the over the years, almost two years, “explained Dobaño.
The researchers evaluated the persistence of IgM, IgA and IgG antibodies directed against the Spike (S) and Nucleocapsid (N) protein of the virus in samples from 247 symptomatic and unvaccinated people taken at eight different times between summer 2020 and November 2021.
The results show, as expected, a gradual and considerable decline in antibody levels, but over 90% of the participants still had antibodies against the five viral antigens tested at each point in the study.
Even in the 23 people not yet vaccinated in November 2021, seropositivity remained at 95%.
Only eight reinfections were observed during the follow-up period, suggesting that immunity is robust and long-lasting even against new variants such as alpha and delta.
Researcher from the Catalan Institute of Health of Central Catalonia, Anna Ruiz-Comellas, stressed that “the study was conducted before the arrival of the omicron variant”.
Age and being a smoker, lower levels of antibodies
The analysis of the samples taken shortly before the start of vaccination confirms what has been observed in previous studies: age and being a smoker are associated with lower levels of antibodies, while hospitalization and some symptoms (fever, loss of taste and smell) are associated with higher levels.
“This would also explain why we are seeing such long-lasting HIV-positive conditions in this study, since all infections recorded in healthcare workers were symptomatic,” Dobaño pointed out.
The results suggest that maintaining detectable levels of antibodies (particularly anti-Spike IgG) confers protection against reinfection even in the absence of vaccination.
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However, the researchers warn that this study was conducted before the arrival of the omcron, and that previously infected people also benefit from vaccination, as hybrid immunity is the one that best protects against infection and disease.
