Section 1.1: U.S. Data Analysis

Utilizing the TriNetX research network, which encompasses data from 59 healthcare organizations primarily in the U.S., Taquet et al. examined a cohort of 273,618 Covid-19 patients (mean age: 46 years; 57% women). The findings revealed that Covid-19 patients were 1.6 times more likely to report at least one persistent symptom compared to those who had influenza. However, the focus here will be on symptom trajectory rather than prevalence.

The data indicated a notable decline in long-Covid symptoms from the initial 90 days to the subsequent 90 days:

• Anxiety or depression: from 22.8% to 15.5% (32% decrease)
• Abnormal breathing: from 18.7% to 7.9% (58% decrease)
• Abdominal symptoms: from 15.6% to 8.3% (47% decrease)
• Fatigue or malaise: from 12.8% to 5.9% (54% decrease)
• Chest or throat pain: from 12.6% to 5.7% (55% decrease)
• Other pain symptoms: from 11.6% to 7.2% (38% decrease)
• Headache: from 8.7% to 4.6% (47.1% decrease)
• Cognitive symptoms: from 7.9% to 4% (49% decrease)
• Muscle pain: from 3.2% to 1.5% (53% decrease)

Consequently, if you develop long-Covid symptoms shortly after your Covid-19 diagnosis, your likelihood of recovery within the first three months is approximately 50%.

Section 1.2: Insights from the U.K.

The U.K. Office of National Statistics (ONS) has tracked over 20,000 Covid-19 survivors as of April 2021, revealing that recovery rates stand between 33% and 43% within the first three months. Specifically, around 21% reported symptoms five weeks post-Covid, which declined to 14% by the 12-week mark and 12% by the 16-18 week mark, reflecting a 33% and 43% reduction from the initial five weeks.

However, this analysis lacks a control group to assess the background prevalence, suggesting that the reported long-Covid rates may be slightly inflated.

Section 2.1: Data from Spain

A study by Fernández-de-las-Peñas et al. involved 1,563 previously hospitalized Covid-19 patients from five hospitals in Spain (mean age: 61 years; 46% women), who were interviewed at 8.4 and 13.2 months post-hospitalization. The results indicated:

• 19% reported no symptoms at 8.4 months, increasing to 32% at 13.2 months (a 68% rise in recovery)
• 48% experienced three or more long-Covid symptoms at 8.4 months, dropping to 25% at 13.2 months (a 48% reduction)

Though this study also lacked a control group, it demonstrates that the chances of recovering fully or partially from long-Covid within eight months are 68% and 48%, respectively. The strength of this study lies in its random sampling, which helps minimize bias and ensures a representative sample of previously hospitalized patients.

Section 2.2: Data from the Netherlands

In a study conducted in the Netherlands, Wynberg et al. followed 192 Covid-19 survivors, categorized by illness severity: 29% mild, 42% moderate, 16% severe, and 12% critical. The findings highlighted that:

• At 12 weeks post-Covid, 31%, 64%, and 87% of mild, moderate, and severe/critical Covid-19 survivors reported long-Covid symptoms, respectively.
• The median recovery time for mild cases was 63 days, with 16% still experiencing long-Covid symptoms one year later (a 48% decrease from 31%).
• For moderate cases, median recovery was 232 days, but 49.5% reported persistent symptoms at one year (a 23% decrease from 64%).
• Severe cases showed 53.5% still experiencing long-Covid after one year, a 38.5% decline from 87% at 12 weeks.

This research indicates that recovery rates diminish with increased severity of the initial Covid-19 illness. Additionally, recovery was found to be 35% slower in women and 38% slower in individuals with obesity after adjusting for confounding factors.

Section 2.3: Data from Italy

In a nine-month follow-up study in Italy, Righi et al. assessed 465 Covid-19 survivors (46% female, mean age: 56 years; 51% hospitalized). The outcomes revealed:

• 42% experienced persistent symptoms at one month, which decreased to 20% by nine months (a 52% reduction).
• Factors such as age over 50, ICU admission, and presenting four or more initial Covid-19 symptoms increased the likelihood of long-Covid by 2-2.5 times.

Pre-Covid, 90% of participants reported excellent physical health, which fell to 24% during their illness and rose to 82% at the nine-month mark (a 73% decrease followed by a 71% increase). This study similarly suggested a recovery likelihood of about 50-70% from one to nine months, decreasing with age and illness severity.