The Omicron variant of the coronavirus has led to a surge in Covid-19 infection across the globe. The heavily-mutated strain is believed to bypass the existing vaccines and give stronger infection to the host.
Yet, there are some people who do not catch the virus despite living with a person who has Covid-19. How is it possible?
A new study has explored thig angle, claiming that such people may be exposed to other coronaviruses in the past that enabled them to make memory immune cells – called T cells. They offer a higher protection against Covid-19.
“Cross-reactive immune responses to SARS-CoV-2 have been observed in pre-pandemic cohorts and proposed to contribute to host protection,” said the study published in Nature, which studied 52 Covid-19 household contacts to capture their immune responses. The idea was to capture immune responses at the earliest timepoints after exposure to Sars-CoV-2 virus.
The researchers noted that viruses from the coronavirus family, though causes different illnesses, have some shared characteristics.
Their shared structural similarities enable immune cells that recognize one type of coronavirus to recognize another type, said the study.
The blood of all the 52 household contacts was tested between day one and day six. The researchers found higher levels of memory T cells in the samples of those who tested negative on a PCR test for Covid-19 than those who tested positive.
The T cells that they measured not only targeted the spike protein part of the virus but also the nucleocapsid, the core part of the virus that stores its genetic material, the researchers said.
Meanwhile, an infectious disease expert had said earlier this week that vaccinated people and those who have not taken a jab, experience different Omicron symptoms.
“There is little systematic data so far, but I expect that many vaccinated and especially boosted folks are experiencing very mild symptoms and there is a higher proportion of vaccinated folks who have no symptoms,” Dr Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco, told KSN.com.
Dr Maya N Clark-Cutaia, professor at the New York University Meyers College of Nursing, said vaccinated people are reporting headaches, body aches and fever when infected with Omicron. Unvaccinated patients are more frequently reporting cough, shortness of breath and flu-like symptoms, she added.
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