Study shows COVID-19 rates were likely forty-times higher than CDC estimates during BA.4/BA.5 dominant period in the U.S.

By Dr. Chinta SidharthanReviewed by Benedette Cuffari, M.Sc.Feb 27 2023

In a recent study published in Preventive Medicine, researchers evaluate the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and the incidence of long coronavirus disease (long COVID) during the surge of the SARS-CoV-2 Omicron subvariants BA.4/BA.5 in the United States.

Study: The prevalence of SARS-CoV-2 infection and long COVID in US adults during the BA.4/BA.5 surge, June–July 2022. Image Credit: Cryptographer / Shutterstock.com

Background

Over two years after the onset of the coronavirus disease 2019 (COVID-19) pandemic, the emergence of SARS-CoV-2 variants with novel mutations enabling immune evasion, combined with the waning of vaccine-induced immunity, persists the risk of COVID-19-associated morbidity and mortality.

Although early efforts to develop COVID-19 vaccines and a worldwide impetus to vaccinate the global population significantly reduced the severity of SARS-CoV-2 infections and global mortality rates, the public health measures for COVID-19 surveillance have not kept up with the rate at which novel SARS-CoV-2 variants are emerging.

The decline in diagnostic screening rates and increase in at-home testing using rapid antigen tests could underestimate the true infection rates. Surveillance based on exposures and symptoms could also present a non-representative sample of the general population.

Surveillance measures also need to evolve to accommodate the long-lasting effects of severe COVID-19. Therefore, as the pandemic evolves, population-based surveys are essential for providing true estimates of infection rates and incidences of long COVID.

About the study

In the present study, the researchers conducted a bilingual and cross-sectional survey among U.S. adults above the age of 18 through mobile phones and landlines for four days starting July 30, 2022. An iterative weighting method was used to ensure that selected participants represented the races, ethnicities, age groups, genders, and education levels of the general population.

The questionnaire determined the results from rapid antigen, at-home test kits, and polymerase chain reaction (PCR) tests in the two weeks leading up to the survey, which was when Omicron BA.4/BA.5 subvariants were the dominant circulating strains of SARS-CoV-2.

The survey also gathered data on COVID-19 symptoms and close contacts that had probable or confirmed SARS-CoV-2 infections. The queried list of symptoms included fever, nasal congestion or runny nose, cough, fatigue, dyspnea, headaches, body aches, anosmia, ageusia, nausea, diarrhea, and sore throat.

Information on comorbidities and vaccination status was also obtained. To this end, participants were categorized as vulnerable if they were unvaccinated or reported one or more comorbidities.

The point prevalence of COVID-19 was estimated for confirmed, probable, and possible cases based on self-reported positive test results and close contact with confirmed cases. Furthermore, four immunity categories were created based on vaccination status and previous SARS-CoV-2 infections, ranging from individuals who had no immunity to individuals who had hybrid immunity from vaccinations and previous SARS-CoV-2 infections.

The point prevalence of long COVID was also estimated based on participants who had previous SARS-CoV-2 infections and confirmed symptoms such as fatigue, dyspnea, and difficulty concentrating that persisted for more than four weeks after recovering from COVID-19.

Study findings

About 17% of study participants reported being infected with SARS-CoV-2 during the Omicron BA.4/BA.5 dominant period. This equates to 44 million cases, which is much higher than the 1.8 million cases estimated by the U.S. Centers for Disease Control and Prevention (CDC) during that period.

When the prevalence of SARS-CoV-2 infections was analyzed according to sociodemographic factors, adults between the ages of 18 and 24 had a higher incidence of infections, as did non-Hispanic Black and Hispanic adults. The prevalence of infections also varied according to income and education levels, with groups with lower income and lower education having a higher incidence of SARS-CoV-2 infections.

Approximately 21.5% of the patients who had SARS-CoV-2 infection four weeks before the survey reported experiencing long COVID symptoms. This estimate was higher than the 18.9% estimate for long COVID incidence reported by the Household Pulse Survey.

Moreover, in contrast to previous studies, the prevalence of long COVID among older individuals was found to be lower than that among younger individuals. This may be attributed to the current study not being restricted to individuals who had accessed medical care or were hospitalized.

Conclusions

The prevalence of SARS-CoV-2 infections and incidence of long COVID among adults above the age of 18 in the U.S. was found to be higher than previous estimates that were primarily focused on hospitalized patients and those seeking medical care.

Notably, the prevalence of SARS-CoV-2 infections varied based on sociodemographic factors such as race, age, income, and education levels. This inequity in infection prevalence during the surge of Omicron BA.4/BA.5 will likely result in an inequitable incidence of long COVID in the future.