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Omicron infections are seen in both vaccinated and unvaccinated people as well as those who have had Covid-19 earlier. But a study by researchers at the University of California, San Francisco (UCSF) has suggested that an omicron infection in fully vaccinated people enhances their pre-existing immunity elicited by the vaccines and enhances protection against other coronavirus variants.
However, an omicron infection in unvaccinated people does not produce antibodies that can effectively neutralise other coronavirus variants, said the researchers in their paper on medRxiv on Tuesday. The study, which is based on lab animal experiments, is yet to be peer-reviewed.
Melanie Ott, a senior investigator at the Gladstone Institute of Virology and Immunology at the UCSF, and her colleagues compared antibodies-containing sera samples from omicron-infected mice and sera from delta-infected mice. They found that while delta infections effectively induce immunity against itself and other variants, including omicron, sera from omicron-infected mice only neutralised omicron.
Further analysis of human sera from omicron and delta breakthough cases showed effective neutralisation induced by both variants in vaccinated individuals.
Based on these findings, the UCSF researchers suggested that vaccinated people whether infected with omicron or delta acquire immune protection against the other strain and other known variants.
Ott and her team believe that a vaccine that incorporates both omicron and delta-based immune responses would provide broad immunity against multiple variants.
The highly transmissible omicron variant is driving the current Covid-19 surges worldwide. Although vaccinated people are also getting infected with the virus, vaccines are proving high protection against severe infection.
Several studies have shown that vaccinated individuals are at a much lower risk of being hospitalized or dying from the omicron infection.
"Current vaccines are expected to protect against severe illness, hospitalizations, and deaths due to infection with the Omicron variant. However, breakthrough infections in people who are fully vaccinated are likely to occur. With other variants, like Delta, vaccines have remained effective at preventing severe illness, hospitalizations, and death. The recent emergence of Omicron further emphasizes the importance of vaccination and boosters," the US CDC says in its website.
The World Health Organization (WHO) also states that current vaccines remain effective against severe disease and death.
With inputs from agencies
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