As the more infectious BA.5 Omicron variant of the coronavirus carries key mutations that help it escape antibodies generated by both vaccines and prior infection, more people are left vulnerable to reinfection and might suffer from "long COVID" symptoms. 

The number of people with long COVID is increasing as more people are infected or experiencing reinfections, said a report published in The Lancet in August. 

With data collected from more than 76,000 people in the Netherlands between April 2020 and August 2021, the study suggests that 12.7 percent of people experienced at least one symptom of long COVID after infection. 

The non-medically termed health complication was first identified by the World Health Organization (WHO) as a post COVID-19 condition that lasts for weeks or months after the infection has gone. It usually comprises of a variety of symptoms that include fatigue, breathlessness and cognitive dysfunction – confusion, forgetfulness or a lack of mental focus and clarity, for example. 

Dr. Ziyad Al-Aly, a clinical epidemiologist at Washington University in St. Louis, said that the increased health risks after COVID-19 infection is in contrast to what people used to think. 

"There is this idea that if you had COVID before, your immune system is trained to recognize it and is more equipped to fight it, and if you're getting it again, maybe it doesn't affect you that much, but that's not really true," Al-Aly said as reported by CNN in July. 

"Each infection brings new risk, and that risk adds up over time," he said. 

Long COVID is also severely affecting economic production.

The Australian Treasury revealed last month that the long COVID cost the country's economy 3 million working days in the first half of this year. About 31,000 Australian workers a day called in sick in June because of the condition during its winter peak, it said. 

In the U.S., approximately 1 million Americans have been forced to leave the labor market because of the long COVID conditions, according to a hearing held by the Select Subcommittee on the Coronavirus Crisis in July.