A new case-control study of Brazilian healthcare workers (HCWs) suggests as many as 27% developed long COVID after infection, and multiple infections raised the risk. The findings were published today in Infection Control & Hospital Epidemiology.
Estimates of the prevalence of long COVID, defined by the Centers for Disease Control and Prevention as new, returning, or lasting symptoms persisting 4 or more weeks after initial COVID-19 infection vary, with some studies showing as many as 43% of infected people will have some lingering symptoms 1 month after COVID-19 confirmation.
Because HCWs have occupational exposure to COVID-19 and were vulnerable to infections the pre-vaccination era of the pandemic, they may be uniquely primed for developing long COVID.
The study is based on confirmed symptomatic COVID-19 HCWs who worked in a Brazilian healthcare system in Sao Paulo from March 1, 2020, to July 15, 2022. Symptoms persisting longer than 4 weeks after acute infection were assessed during 180 days of follow-up.
Half with long COVID had 3 or more symptoms
Researchers included 18,340 HCWs in the study, of whom 7,051 (38.4%) had at least one laboratory-confirmed SARS-CoV-2 infection during the study period. Out of 7,051 HCWs diagnosed as having COVID-19, 1,933 (27.4%) who developed long COVID were compared to 5,118 (72.6%) who had a COVID-19–positive test but did not experience any symptoms at week 4.
Among HCWs with long COVID, just over half (51.8%) reported three or more symptoms 4 weeks after infection. The most common symptoms were headache (53.4%), followed by muscle or joint pain (46.6%) and nasal congestion (45.1%).
Multiple COVID infections were predictive of developing long COVID; Overall, 887 HCWs (12.6%) had two or more SARS-CoV-2 infections, including 17.8% of cases and 10.6% of controls.
Other predictive factors for developing long COVID were female sex (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.05 to 1.39), and older age (OR, 1.01 per year of age; 95% CI, 1.00 to 1.02)
Vaccination tied to lower risk of long COVID
HCWs in the health system were regularly tested for COVID-19 if symptomatic and were among the first populations in Brazil vaccinated against COVID-19 with the Oxford-AstraZeneca, CoronaVac, Pfizer-BioNTech, or Johnson & Johnson vaccines.
We revealed that receiving 4 doses of COVID-19 vaccinations before infection was a protective against long COVID.
The authors of the study found that vaccination was protective against long COVID development, but only among those who got multiple doses. Those who received four vaccine doses before infection (OR, 0.05; 95% CI, 0.01 to 0.19), were much less likely to develop long COVID.
"We revealed that receiving 4 doses of COVID-19 vaccinations before infection was a protective against long COVID, although a dose–response effect was not detected, which could have been due to the small sample size, creating an unbalanced comparison between vaccinated and unvaccinated," the authors concluded.