Most Long-term COVID Effects Resolve Within a Year, Researchers Find

Most symptoms or conditions that develop after a mild Covid-19 infection persist for several months but return to normal within a year, according to a large study from Israel published in The BMJ .

In particular, vaccinated people had a lower risk of breathing difficulties, the most common effect that develops after a mild infection, compared to unvaccinated people.

These findings suggest that, although the long Covid phenomenon has been feared and discussed since the beginning of the pandemic, the vast majority of cases of mild illness do not suffer from severe or chronic long-term illness, the researchers say.

Long Covid is defined as persistent symptoms or new symptoms that appear more than four weeks after the initial infection. In March 2022, approximately 1.5 million people in the UK (2.4% of the population) reported long Covid symptoms, mainly fatigue, shortness of breath, loss of smell, loss of taste and difficulty concentrating.

But the clinical effects of long Covid one year after mild infection and its association with age, sex, Covid-19 variants and vaccination status are still unclear. To address this, the researchers compared the health of uninfected people with those who had recovered from mild Covid-19 for a year after infection.

They used electronic records from a large public healthcare organization in Israel, where nearly 2 million members were tested for Covid-19 between March 1, 2020 and October 1, 2021. They analyzed more than 70 long Covid conditions in a group of infected and uninfected members (average age 25 years; 51% women).

They compared conditions in unvaccinated people, with and without Covid-19 infection, controlling for age, sex and Covid-19 variants, during the early (30-180 days) and late (180-360 days) time periods after of the infection. Conditions in vaccinated versus unvaccinated people with Covid-19 were also compared over the same time periods.

To ensure that only mild illness was evaluated, they excluded patients admitted to the hospital with more severe illness. Other potentially influential factors were also taken into account, such as alcohol consumption, smoking, socioeconomic status, and a variety of pre-existing chronic conditions.

Covid-19 infection was significantly associated with an increased risk of several conditions, such as loss of smell and taste, impaired concentration and memory, breathing difficulties, weakness, palpitations, strep throat, and dizziness in the early and early periods. late period, while hair loss, chest pain, cough, muscle aches and pains and respiratory disorders resolved in the late period.

For example, compared with uninfected people , mild Covid-19 infection was associated with a 4.5 times higher risk of loss of smell and taste (about 20 additional people per 10,000) in the baseline period and a risk almost 3 times higher (11 per 10,000 people) in the late period.

The overall burden of conditions after infection during the 12-month study period was highest for weakness (136 additional people per 10,000) and breathing difficulties (107 per 10,000).

When conditions were evaluated by age, respiratory difficulties were the most common, appearing in five of the six age groups, but remaining persistent during the first year after infection in the age groups 19-40, 41-60 and over 60 years old.

Weakness appeared in four of the six age groups and remained persistent in the late phase only in the 19-40 and 41-60 age groups .

Male and female patients showed minor differences, with children having fewer outcomes than adults during the early phase of Covid-19, which mostly resolved in the late period. The findings were similar in the wild-type, Alpha and Delta Covid-19 variants.

Vaccinated people who became infected had a lower risk of breathing difficulties and a similar risk of other conditions compared to unvaccinated infected patients.

The researchers point out some limitations, such as incomplete measurement within medical records, so the data may not fully reflect reported diagnoses and outcomes. And they cannot rule out the possibility that Covid-19 patients use healthcare services more frequently, resulting in increased reporting and increased detection of potential Covid-related outcomes in these patients.

However, this was a large detailed analysis of health records in a diverse population, representing one of the longest follow-up studies in patients with mild Covid-19 to date. And the findings should apply to similar Western populations around the world.

“Our study suggests that patients with mild Covid-19 are at risk for a small number of health outcomes and most of them resolve within a year of diagnosis,” the researchers say.