A study of more than 16,000 American COVID-19 survivors reveals that 15% still had symptoms 2 months later to 1 year later, but those who were vaccinated were less likely than unvaccinated participants to report such symptoms. The research was published today in JAMA Network Open.
A team led by a researcher from Massachusetts General Hospital and Harvard Medical School in Boston fielded eight online surveys from Feb 5, 2021, to Jul 6, 2022, to adults in 50 states and Washington, DC, who had COVID-19 at least 2 months earlier. Average participant age was 40.5 years, 62.6% were women, 71.0% were White, 11.3% were Black, 9.6% were Hispanic, and 5.1% were Asian. To minimize selection bias, the survey didn't focus only on COVID-19.
Older people, women at greatest risk
Of the 16,091 respondents, 14.7% reported having COVID-19 symptoms more than 2 months after their infections. The long-COVID patients represented 13.9% of COVID-19 survivors (10.1% of men, 17.9% of women). Among all participants, 12.6% of Asian, 9.7% of Black, 15.3% of Hispanic, and 15.5% of White adults reported long-COVID symptoms.
After reweighting, the estimated prevalence of long COVID among the entire US adult population was 1.7%, including 1.3% of men, 2.0% of women, and 0.7% of Asian, 1.0% of Black, 2.0% of Hispanic, and 1.8% of White adults. This would translate into 5.6 million US adults affected by long COVID.
When the analysis was restricted to the 12,441 respondents who tested positive for COVID-19 at least 6 months earlier, 14.8% reported lingering symptoms. Among the 7,462 people who tested positive at least 12 months earlier, 15.2% said they still had long-COVID symptoms.
Risk factors for persistent symptoms included older age per decade above 40 years (adjusted odds ratio [aOR], 1.15) and female sex (aOR, 1.91), while a graduate education versus high school or less (aOR, 0.67) and urban versus rural residence (aOR, 0.74) offered some protection. Maximum risk was seen in the 50- to 59-year age-group, compared with 18- to 29-year-olds (aOR, 2.38).
Compared with the early pandemic period of wild-type SARS-CoV-2 predominance, infection during periods when the Epsilon (OR, 0.81) or Omicron (OR, 0.77) variant prevailed was tied to a lower likelihood of long COVID, as was completion of a primary COVID-19 vaccine series before infection (OR, 0.72). Partial vaccination, however, was not associated with significantly lower risk (OR, 0.93).
Fatigue, cognitive problems common
The most common symptoms were fatigue (52.2%), followed by loss of smell (43.7%), "brain fog" (40.4%), and shortness of breath (39.7%); 45.7% reported either memory loss or brain fog. Women were significantly more likely than men to report loss of smell (46.4% vs 35.3%), cognitive symptoms (48.7% vs 36.3%), anxiety (30.8% vs 22.3%), and sleep disruption (32.4% vs 22.5%).
Loss of smell was reported less often during the Omicron-predominant period than during the Alpha or Delta eras (33.7% vs 40.1% vs 50.5%, respectively), which is in line with previous findings. According to population-weighted estimates, 0.7% of Americans have cognitive symptoms, compared with 6.1% in this study of COVID-19 patients.
The researchers said the findings "support the potential protective association of vaccination in reducing but not eliminating long COVID risk. If confirmed in prospective studies, these results may facilitate risk stratification, with a goal of early intervention to minimize the effect of long COVID, and could contribute to efforts to prevent this syndrome altogether."