A groundbreaking study in the journal Cell proposes that some individuals may already possess immunity to COVID-19 without prior exposure. This intriguing idea sparks debate among experts.
Researchers at leading institutions, including the University of San Diego's Center for Infectious Disease and Vaccine Research, suggest cross-immunity could explain why the pandemic might be waning. Here's what the evidence shows.
The team analyzed blood from 20 COVID-19-exposed but uninfected patients, identifying CD4+ and CD8+ T cells that recognized SARS-CoV-2 proteins like spikes, M, and N. Remarkably, these patients mounted an immune response without infection.
They also tested samples from 20 healthy U.S. donors collected between 2015 and 2018—pre-COVID era. About half contained CD4+ T cells reactive to SARS-CoV-2 proteins.
Unable to stem from COVID-19 exposure, this response likely arises from prior mild infections with related coronaviruses. Cross-immunity occurs when immunity from one virus protects against a genetically similar one, as detailed in peer-reviewed research.
The study estimates 40% to 60% of the population could be immune, limiting SARS-CoV-2's spread. With high initial virulence and infections, this could signal the virus is declining, potentially averting a devastating second wave.
Epidemiologist Laurent Toubiana of IRSAN echoes this: "A significant portion may be resistant. The wave has peaked, infecting the susceptible, and the epidemic is ending," he told France Inter.
"This virus is a sprinter, not a marathoner—it burns out fast," adds Professor Jean-François Toussaint of IRMES.
Positive trends support this: ICU admissions dropped since April 8, as have daily deaths—likely aided by containment. Yet experts urge vigilance.
Public Health France's Daniel Lévy-Bruhl warns AFP: "No alarms now, but too soon to declare victory. The risk of resurgence lingers." He deems cross-immunity hopes premature, unconfirmed, and not consensus.
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