KFAR MALAL, Israel — Most symptoms of long COVID clear up within a year following a mild infection, according to a new study.
Researchers in Israel say a relatively mild case of the virus does not lead to substantial long-term illness in most infected people. Their findings, published by The BMJ, show that most symptoms that develop after a mild COVID-19 infection linger for several months, but return to normal within 12 months. Vaccinated people, in particular, were at a lower risk of breathing difficulties — the most common symptom to develop after mild infections.
The findings also suggest that, although the long COVID phenomenon has been feared and discussed since the beginning of the pandemic, the vast majority of mild disease cases do not suffer serious or chronic long-term illness. Long COVID is a condition where lingering symptoms or new symptoms appear more than four weeks after a patient’s initial COVID infection.
In March 2022, an estimated 1.5 million people in the United Kingdom (2.4% of the population) reported experiencing long COVID symptoms. These included fatigue, shortness of breath, loss of smell, loss of taste, and difficulty concentrating. However, the clinical effects of long COVID one year after mild infection and their association with age, sex, COVID variants, and vaccination status were still unclear.
What symptoms should COVID patients look for?
The Israeli research team compared the health of uninfected people with those who had recovered from a mild case of COVID a year ago. They used electronic records from a public healthcare organization in Israel, in which almost two million members were tested for COVID-19 between March 1, 2020 and Oct. 1, 2021.
More than 70 long COVID conditions were analyzed among a group of infected and matched uninfected members with an average age of 25. The researchers compared conditions in unvaccinated people, with and without COVID-19 infection, controlling for age, sex, and coronavirus variants, during early (30 to 180 days) and late (180 to 360 days) time periods after infection.
Conditions in vaccinated compared to unvaccinated people with COVID were also compared over the same time periods.
To ensure only mild disease was assessed, the team excluded patients admitted to hospitals with more serious illness. Other potentially influential factors, such as alcohol intake, smoking, socio-economic status, and a range of pre-existing chronic conditions, were also taken into account.
The researchers found that COVID-19 infection was “significantly associated” with increased risks of several conditions including loss of smell and taste, concentration and memory impairment, breathing difficulties, weakness, palpitations, streptococcal tonsillitis, and dizziness in both early and late time periods. Hair loss, chest pain, cough, muscle aches and pains, and respiratory disorders resolved in the late period.
For example, compared with non-infected people, a mild COVID infection was associated with a 4.5-fold higher risk of smell and taste loss in the early period and an almost three-fold higher risk in the later period.
Breathing difficulties are the most common problem
The findings show that the overall burden of conditions after infection across the 12-month study period was highest for weakness and breathing difficulties. Study author Dr. Maytal Bivas-Benita says when conditions were assessed based on age, breathing difficulties were the most common symptom, appearing in five of the six age groups but remaining persistent throughout the first year post-infection in the 19 to 40, 41 to 60, and over 60 age groups.
The researcher adds that weakness appeared in four of the six age groups and remained persistent in the late phase only in the 19 to 40 and 41 to 60 age groups. Male and female patients showed minor differences, and children had fewer adverse outcomes than adults during the early phase of COVID-19, and these issues generally resolved in the late period.
The team from the KI Research Institute report that there were similar results across the wild-type, Alpha, and Delta COVID-19 variants. They add vaccinated people who became infected had a lower risk of breathing difficulties and similar risk for other symptoms compared with unvaccinated patients with COVID.
However, the team notes that they can’t rule out that COVID patients may use healthcare services more frequently, resulting in higher reporting and increased screening for potential COVID-related symptoms.
“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 say in a media release.
“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.”
South West News Service writer Mark Waghorn contributed to this report.