Study shows Covid-19 antibodies may last only few weeks

The study showed that 28 of those tested positive had no antibodies in a sero survey done weeks later.

A study conducted on 801 frontline medics in India showed that Covid-19 antibodies may not last more than a couple of months.
The study was carried out on affected healthcare staff of JJ Group of Hospitals and showed that 28 of those tested positive had no antibodies in a sero survey done weeks later.    
"Our study of 801 healthcare staff from JJ, GT and St George's Hospitals included 28 who had tested positive for Covid (on RT-PCR) seven weeks prior (in late April-early May)," said the study's main author Dr Nishant Kumar. 
However, none of the 28 showed any antibodies in a sero survey done in June, according to the preprint of the study that will appear in the September issue of the 'International Journal of Community Medicine and Public Health'.
The JJ Hospital sero survey had 34 others who tested PCR positive for Covid three weeks and five weeks prior respectively. "While 90 per cent of those in the three-week group had antibodies, less than half (38.5 per cent) in the five-week group had antibodies,'' said Dr Kumar.
Moreover, in June Dr Kumar's not-for-profit Eyebetes Foundation along with state-run JJ Hospital in Byculla carried out a survey that showed that one in 10 staffers was sero-positive or had had previous exposure to the virus. But a further analysis of the same survey's results showed that antibodies decayed quickly. 
However, some public health experts were not convinced with the early decay of antibodies as studies in the West have shown asymptomatic patients do not have the same level of antibodies as patients who have had a prolonged or severe Covid infection.
"We don't know if the 28 patients in the JJ study had suffered asymptomatic form of Covid or if they had symptoms. Patients who had longer symptomatic disease have antibodies for at least three to four months," said epidemiologist Giridhar R Babu from the Public Health Foundation of India.