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NEW DELHI: Recovered Covid-19 patients have immunity from the novel coronavirus for up to eight months, a new study has found. The study, published in journal _Science _Wednesday, was

conducted using samples from 188 Covid cases across the US, at the La Jolla Institute of Immunology. “If we had seen only marginal immune responses, we would have been concerned,” Alessandro

Sette, professor, Center for Infectious Disease and Vaccine Research, said in a statement. Show Full Article “…but what we see is a very robust T cell response against the spike protein,

which is the target of most ongoing COVID-19 efforts, as well as other viral proteins. These findings are really good news for vaccine development,” Sette added.   While the duration of

immune response to the virus has been studied throughout the pandemic, a study by King’s College London had worryingly found that antibody levels that can destroy the virus peaked about

three weeks after the onset of symptoms. However, cases of reinfection remain rare across the world. ------------------------- _ALSO READ: India will be able to vaccinate entire population

soon, says Harsh Vardhan_ ------------------------- METHODOLOGY The latest study was conducted on 254 samples from 188 Covid cases. The subjects included 80 males and 108 females, aged

between 19 and 81 years, and represented a range of asymptomatic, mild, moderate, and severe Covid cases. However, most subjects had mild Covid cases with 93 per cent never requiring

hospitalisation. The rest included those who required ICU care. Ninety seven per cent of the subjects, however, were symptomatic. Samples were collected from the subjects between 6 days and

240 days post symptom onset (PSO), with 43 samples which were at over six months after infection. IMMUNITY MEMORY The study focused on the following five immune memory responses: RBD IgG,

RBD memory B cells, Spike IgA, total SARS-CoV-2-specific CD8+T cells, and total SARS-CoV-2-specific CD4+ T cells. These are types of white blood cells which help in immune responses. Over

every three out of five Covid cases were positive for all five of these immune memory compartments at one to two months PSO. At five to eight months PSO, the proportion of individuals

positive for all five of these immune memory compartments had dropped to 43 per cent; but 95 per cent of individuals were still positive for at least three out of five immune memory

responses. Immune memory at five to eight months PSO represented contributions from different immune memory compartments in different individuals. “Our data show immune memory in at least

three immunological compartments was measurable in 95% of subjects 5 to 8 months PSO, indicating that durable immunity against secondary COVID-19 disease is a possibility in most

individuals,” the study said. ------------------------- _ALSO READ: IMA ‘welcomes’ Covid-19 vaccines, encourages doctors across India to get vaccinated_ -------------------------