While many countries are considering ‘immunity passports’ to allow recovered COVID-19 patients to travel more freely, researchers have warned that antibodies against SARS-CoV-2 may not last long.
Are people who have recovered from COVID-19 and have antibodies protected against reinfection? This is one of the frequently asked questions about this deadly disease. While it was still unclear if recovered COVID-19 patients may become immune to the disease or not, many countries had already started considering providing ‘immunity passports’ to allow them to travel more freely. This decision may need reconsideration as new research has suggested that immunity to SARS-CoV-2 may last only for two-six months. Also Read – COVID-19 Live Updates: Cases in India surge to 4,10,461 as death toll reaches 13,254
According to a study published in the journal Nature, asymptomatic COVID-19 patients show a decline in antibodies within 2-3 months. The study done in China evaluated the clinical and immunological features of the disease in asymptomatic COVID-19 patients. It was also found that most asymptomatic patients shed the virus for an average of 19 days, which suggests that patients without symptoms can play a major role in spreading the disease. Previous research has revealed that symptomatic group can continue to shed the COVID-19 virus for as long as 14 days. Also Read – Many new moms suffering from depression, anxiety amidst COVID-19 pandemic: Here’s why
Further, the researchers followed 37 asymptomatic and 37 symptomatic people for eight weeks they were discharged from the hospital. They were surprised to find that symptomatic patients have stronger immune response to the virus than asymptomatic people. They found that levels of Immunoglobulin G (IgG) – antibody that protects against bacterial and viral infections – dropped in about 93 percent asymptomatic COVID-19 patients and about 96.8 percent symptomatic people in the early convalescent (recovery) phase. However, a higher number of IgG was seen in symptomatic people. IgG is known to be responsible for long-term response against a pathogen. Also Read – Living in crowded homes, poor neighbourhoods increases your risk of catching COVID-19
Also, as many as 81 percent of asymptomatic patients and 62 percent of the symptomatic ones showed decline in neutralising antibodies – the antibodies that bind to the virus and stop the infection.
Immunity Declines By 50 Percent In Six Months
A previous study on coronaviruses that cause the common cold had showed a significant reduction (about 50 percent) in antibody levels among the recovered patients within six months and reinfection within a year. This small study was done in Amsterdam, where 10 patients were followed up with for as long as 35 years to see how their body reacts to coronaviruses and for how long they continue to remain immune to the viruses. The study found that their antibody levels dropped by about 75 percent within a year and half of them had no immunity against the virus after four years.
The study concluded that since SARS-CoV-2 is also a member of the coronavirus family and shares many characteristics, the possibility of reinfection among recovered patients is high. However, it is only when the person is exposed to the virus again.And if there is high chance of reinfection, serological testing for COVID-19 would be of no value if done a year after the infection – noted the researchers, suggesting the requirement for frequent vaccination – for example every six months to maintain sustained immunity.