Antibodies produced in those infected with Covid-19 do not ensure protection from reinfection of SARS-CoV-2, revealed a study published in the Science Journal. The study has however highlighted that robust neutralizing antibodies to SARS-CoV-2 infection persist for 2 to 5 months.
Scientists reported that the vast majority of infected individuals with mild-to-moderate Covid-19 experience robust IgG antibody responses against the viral spike protein, based on a dataset of 30,082 individuals screened at Mount Sinai Health System in New York City. “We find stable antibody titers (a measurement of how much antibody an organism has produced) over a period of at least 3 months and only modest declines at the 5-month time point,” the study said adding that it is still unclear if infection with SARS-CoV-2 in humans protects from reinfection and for how long.
“Although this (antibody longevity) cannot provide conclusive evidence that these antibody responses protect from reinfection, we believe it is very likely that they will decrease the odds ratio of reinfection, and may attenuate disease in the case of breakthrough infection,” the study said.
A breakthrough infection is a case of a medical condition in which a vaccinated individual becomes sick from the same illness that the vaccine is meant to prevent.
Scientists have called for further studies in this regard. “It is imperative to swiftly perform studies to investigate and establish a correlate of protection from infection with SARS-CoV-2. A correlate of protection, combined with a better understanding of antibody kinetics to the spike protein, would inform policy regarding the Covid-19 pandemic and would be beneficial to vaccine development efforts,” the study said.
Several other global studies have shown that the antibodies also decline rapidly in an individual infected with Covid-19. Dr Francis Collins director of the National Institutes of Health in Bethesda, Maryland, United States in his latest post has said that the early data brought hope that acquired immunity was possible. But some subsequent studies have suggested that immune protection might be short-lived.
Though more research is needed, the results of two recent studies, published in the journal Science Immunology, support the early data and provide greater insight into the nature of the human immune response to this coronavirus, Collins said.
The new findings show that people who survive a Covid-19 infection continue to produce protective antibodies against key parts of the virus for at least three to four months after developing their first symptoms. In contrast, some other antibody types decline more quickly. The findings offer hope that people infected with the virus will have some lasting antibody protection against re-infection, though for how long still remains to be determined, Collin said in his post.
Still, there are rare reports of individuals who survived one bout with Covid-19 and were infected with a different SARS-CoV-2 strain a few weeks later. The infrequency of such reports, however, suggests that acquired immunity after SARS-CoV-2 infection is generally protective, Collins said adding that there remain many open questions, and answering them will require conducting larger studies with greater diversity of Covid-19 survivors. In India the Indian Council of Medical Research (ICMR) is also studying the reinfection episodes among those who have got Covid-19 infection.
“We can’t say with absolute certainty that antibodies can prevent Covid-19 reinfection. We have however seen that in few people with antibodies develop Covid-19 like symptoms 4-6 weeks after recovery from Covid-19 and consider it as reinfection. On detailed investigation turns out to be other viral, bacterial or fungal respiratory infection, due to post Covid-19 low immune status,” said Dr Akshay Budhraja, Consultant Department of Pulmonology, Aakash Healthcare Super Speciality Hospital.