The share of Americans reporting symptoms of long COVID appears to be declining, according to a new report from the Kaiser Family Foundation (KFF), and a second study reports that vaccination may contribute to lower levels of long COVID.
Limitations of daily activities in 79%
The KFF analysis of the Household Pulse Survey, on online survey administered by the Centers for Disease Control and Prevention (CDC), found that the percentage of respondents who have had COVID-19 and currently report long COVID symptoms declined from 19% in June 2022 to 11% in January, and the share of people who have ever reported long COVID fell from 35% to 28% over the same period.
The change could stem from changes in SARS-CoV-2, the virus that causes COVID, or from increasing population immunity through vaccination and prior infection.
As of Jan 16, 15% of all US adults reported having had long COVID symptoms at some point, and 6% reported current symptoms. Among people with long COVID, 79% report having limitations to their day-to-day activities, while only 27% say those limitations are significant.
"Longer-term, it is unclear what is driving the reduced percentage of people with COVID who report having long COVID and whether current trends will continue," the report states. "The change could stem from changes in SARS-CoV-2, the virus that causes COVID, or from increasing population immunity through vaccination and prior infection."
The KFF analysis notes that it is unclear how well the Pulse survey respondents represent all US adults.
Study suggests vaccine benefit
Meanwhile, in a study published today in Clinical Infectious Diseases, US researchers, including CDC experts, report that differences in severe fatigue and other prolonged symptoms following SARS-CoV-2 infection during the pre-Delta period compared with the Delta and Omicron periods may have less to do with the characteristics of the variants than other factors, especially COVID vaccination.
The multicenter prospective study by researchers with the Innovative Support for Patients with SARS-CoV-2 Infections Registry (INSPIRE) compared fatigue severity, fatigue symptoms, individual and organ system-based symptoms, and the presence of three or more prolonged symptoms across variants among COVID-positive and COVID-negative participants 3 months after their initial diagnosis. The variant-dominant periods were defined by dates for which the variant accounted for more than 50% of cases.
Of the 3,223 participants in the study, 2,402 (66.6% female, 71.1% White) were COVID-positive and 821 were COVID-negative. Of the COVID-positive cohort, 463 (19.3%) were infected pre-Delta, 1,198 (49.9%) during Delta, and 741 (30.8%) during Omicron. Prolonged severe fatigue at 3 months was highest in the pre-Delta COVID-positive cohort compared with the Delta and Omicron cohorts (16.7% vs 11.5% vs 12.3%, respectively), as was the presence of three or more prolonged symptoms (28.4% vs 21.7% vs 16.0%).
After adjusting for socio-demographics, clinical characteristics, and vaccination status, however, the differences in prolonged severe fatigue and other symptoms between variants were not significant, "suggesting that differences in prolonged symptoms between variants might be a function of these factors in addition to or perhaps instead of characteristics of each variant," the study authors wrote.
The authors note that people infected with Delta or Omicron might have a different distribution of symptoms post-illness, but no significant difference in fatigue severity or symptom quantity after accounting for vaccination status.
"This suggests a potential beneficial effect of vaccination on the risk of developing long-term symptoms," they wrote.