NEW DELHI: After a UK study suggested that immunity generated in recovered Covid patients may not be long-lasting, experts asserted that this points to the growing evidence that the infection could become endemic.
Experts also said that the research findings imply that a vaccine, when available, may be required to be taken annually.
In the UK study, immune response of over 90 patients and healthcare workers showed that antibodies — which can destroy the virus — peaked about three weeks after the onset of symptoms and then dropped rather swiftly.
While 60% of them had very potent antibody response at the height of infection, only 17% retained the same potency three months later. Also, antibody levels declined as much as 23-fold over the period. In some cases, there were no detectable antibodies at all.
Specialists said this is a good study which shows that neutralisation titters come down to baseline values in about four months post onset of symptoms.
“In simple terms, this would mean loss of protection after some months,” said virologist and Wellcome Trust DBT India Alliance CEO Dr Shahid Jameel.
There is also cellular responses also creates a memory for the pathogen, which is recalled when exposed again, he said.
“So, it’s also important to see how fast that response comes up to limit disease on fresh exposure and that is not addressed in this work.”
The findings do not bode well for a vaccine, he said. “If natural infection leads to short term protection, a vaccine may not do any better. The virus will become endemic like other human cold causing corona viruses and vaccines may have to be taken annually.”
Senior virologist Dr Jayaprakash Muliyil said that it’s a good thing that SARS CoV 2 triggers a good immunogenic response.
“While we are still understanding how long the protection lasts, evidence so far is that the antibodies are linked with T-Cells which are memory cells. I am hopeful that once infected, people will not likely get a severe disease again.”
On other hand, an immunologist associated with a research group under the Indian Council of Medical Research said that there was still no robust and conclusive evidence on the immunogenic response against the disease and understanding about it will take some time to evolve.