After recovering from COVID-19, some people continue to feel the aftershocks for weeks or months on end despite testing negative for the virus. They often suffer from symptoms such as fatigue and nausea. These are the cases that are most likely to be classified as COVID long-haulers.What is long COVID?It is a post-COVID syndrome. This term is used to describe effects that linger on for weeks or months after a person tests positive for the novel coronavirus. According to the Johns Hopkins’ Bloomberg School of Public Health, long COVID is a chronic state of infection. “These are individuals who have post-acute sequelae (or symptoms) 30 days or more after their initial infection.”Also read: How does COVID affect the brain? Two neuroscientists explainWhat causes long COVID?Research led by John Arthur, a professor of nephrology at the University of Arkansas for Medical Science, has shown that “antibodies that linger after an infection has been cleared may be causing the immune system to mistakenly attack the body.” This is just one of the many hypotheses on the underlying causes of long COVID, more research is being done around the world to better understand this phenomenon.Also read: Long COVID-19 affects 10 percent to 30 percent of all COVID-19 patients: ReportWhat are the symptoms of long COVID?Shortness of breath, chest pain, concentration issues, insomnia, fatigue, tinnitus, stomach ache, loss of appetite, skin rashes, sore throat, coughs and headaches are some of the symptoms that could persist for many weeks or months.Is there a treatment for long COVID?According to an article published by US News, some long-haulers have claimed that vaccines against COVID-19 relieved few of their symptoms. But researchers across the world, including those at Johns Hopkins, say it is too early to say anything.A support group for COVID long-haulers, Survivors Corps, has documented numerous members who say vaccines have helped their symptoms, prompting Akiko Iwasaki, an immunologist at Yale University, to launch a study examining the impact of vaccines on long COVID, according to US News.Can children get long COVID?The answer is yes, but according to a report by SCMP, studies have indicated that children are less likely to suffer from persistent symptoms of long COVID than adults.Estimates also vary on how often long COVID symptoms occur in children. A recent study published in the UK found that nearly 4 percent teenagers, including children, had symptoms well after a month, after they were found COVID positive. Among children, fatigue, headaches and loss of smell were the most common complaints. But in most cases, these symptoms went away within two months.Also read: Explained: Why COVID-19 vaccine for children is taking so longCould one get long COVID from an infection acquired after vaccination?Researchers are studying the chances of long-term symptoms developing in anyone who might get infected after vaccination. However, the one thing experts in the field are sure about is that vaccines around the world are effective in preventing severe illness and death from COVID-19.