The persistence of symptoms for weeks and months after infection with SARS-CoV-2, the phenomenon known as long COVID, was a major concern early in the pandemic. Some people who had relatively mild cases of COVID-19 that did not require hospitalization were unable to function for weeks and months, raising fears about an influx of patients with persistent symptoms into healthcare systems.

Some of the concerns came to pass. Long COVID, defined as the presence of symptoms more than four weeks after the initial infection, affected an estimated 1.5 million people in the U.K. in March 2022 and still contributes to the fact that one in 12 working-age adults in Britain have long-term health conditions and are out of work.

However, a study published in the BMJ suggests that most cases of long COVID after mild infection resolve within the first year. The study looked at data on two million members of an Israeli public health organization who were tested for COVID-19 between March 2020 and October 2021. Most symptoms seen in the 180 days after infection resolved over the following 180 days.

Investigators looked at 70 long COVID symptoms in a group of infected and matched uninfected individuals. People hospitalized with COVID-19 were excluded from the study to show the persistence of symptoms after mild cases only.

Between 30 days and 180 days after infection, cases of hair loss, chest pain, cough, muscle aches and pains, and respiratory disorders were elevated in people recovering from COVID-19. However, levels of those symptoms returned to normal over the following 180 days.

Other symptoms remained elevated between 180 days and 360 days. For example, 11 per 10,000 people suffered smell and taste loss over that period, down from 20 per 10,000 people in the first 180 days after infection. The study also reported that the levels of concentration and memory impairment, breathing difficulties, weakness, palpitations, streptococcal tonsillitis, and dizziness remained elevated.

Across the 12-month study, the overall burden was highest for weakness and breathing difficulties. The rate of breathing difficulties, a condition known as dyspnea, was lower in vaccinated people than in unvaccinated individuals.

"Our study suggests that mild COVID-19 patients are at risk for a small number of health outcomes and most of them are resolved within a year from diagnosis," the researchers said. "Importantly, the risk for lingering dyspnea was reduced in vaccinated patients with breakthrough infection compared with unvaccinated people, while risks of all other outcomes were comparable."