Exercise Intolerance in Long Covid After 24 Months From Severe Acute Disease: is There Room for Improvement? (preprint)

Introduction: Long COVID is a complex and multisystemic condition, where dyspnea, fatigue, post-exertional malaise, cognitive impairment, decreased functional capacity, and deterioration in quality of life are the most incident clinical features. Few studies have reported cardiopulmonary alterations 24 months after severe COVID-19 infection.  Objective: to evaluate the functional capacity of individuals with persistent symptoms after severe COVID-19 infection compared to control individuals without symptomatic COVID or mild COVID after 24 months.  Methods: This is a case-control study assessing 34 individuals divided into 2 groups (severe COVID-19 with long COVID and a control group consisting of asymptomatic/mild acute COVID-19 with no long COVID) regarding functional capacity by 6-minute walk test (6MWT) associated with gas analysis, spirometry, respiratory muscle strength and quality of life. Results: During the 6MWT, an important lower heart rate (HR) was observed for the COVID group, with greater exertional perception, a significant decrease in the distance covered, and a low value of O2 uptake (V̇O2) and minute ventilation, in addition to very low quality of life scores, especially in aspects of functional capacity and physical limitations.  Conclusion: individuals who have severe COVID-19 and persist with symptoms have low functional capacity, low V̇O2, low HR behavior, and low quality of life. 

Low handgrip strength is associated with worse functional outcomes in long-Covid (preprint)

The diagnosis of long-Covid is troublesome, even when functional limitations are present. Dynapenia is a decrease in muscle strength and power production and may explain in part these limitations. This study aimed to identify the distribution and possible association of dynapenia with functional assessment in patients with long-Covid. A total of 113 inpatients with COVID-19 were evaluated by functional assessment 120 days post-acute severe disease. Body composition, respiratory muscle strength, spirometry, six-minute walk test (6MWT) and hand-grip strength (HGS) were assessed. Dynapenia was defined as HGS < 30kg/f (men), and < 20kg/f (women). Twenty-five (22%) participants were dynapenic, presenting lower muscle mass (p < 0.001), worse forced expiratory volume in the first second (FEV1) (p = 0.0001), lower forced vital capacity (p < 0.001), and inspiratory (p = 0.007) and expiratory (p = 0.002) peek pressures, as well as worse 6MWT performance (p < 0.001). Dynapenia was associated with worse FEV1, MEP, and 6MWT, independent of age (p < 0.001). Patients with dynapenia had higher ICU admission rates (p = 0.01) and need for invasive mechanical ventilation (p = 0.007) during hospitalization. The HGS is a simple, reliable, and low-cost measurement that can be performed in outpatient clinics in low- and middle-income countries. Thus, HGS may be used as a proxy indicator of functional impairment in this population.

Longitudinal study of humoral immunity against SARS-CoV-2 of health professionals in Brazil: the impact of booster dose and reinfection on antibody dynamics (preprint)

The pandemic caused by SARS-CoV-2 has had a major impact on health systems. Vaccines have been shown to be effective in improving the clinical outcome of COVID-19, but they are not able to fully prevent infection and reinfection, especially that caused by new variants. Here, we tracked for 450 days the humoral immune response and reinfection in 52 healthcare workers from Brazil. Infection and reinfection were confirmed by RT-qPCR, while IgM and IgG antibody levels were monitored by rapid test. Of the 52 participants, 19 (36%) got reinfected during the follow-up period, all presenting mild symptoms. For all participants, IgM levels dropped sharply, with over 47% of them becoming seronegative by the 60th day. For IgG, 90% of the participants became seropositive within the first 30 days of follow-up. IgG antibodies also dropped after this period reaching the lowest level on day 270 (68.5{+/-}72.3, p<0.0001). Booster dose and reinfection increased the levels of both antibodies, with the interaction between them resulting in an increase in IgG levels of 130.3 units. Overall, our data indicate that acquired humoral immunity declines over time and suggests that IgM and IgG antibody levels are not associated with the prevention of reinfection.

Salivary, serological, and cellular immune response to the CoronaVac vaccine in health care workers with or without previous COVID-19.

We investigated the anti-SARS-CoV-2 post-vaccine response through serum and salivary antibodies, serum antibody neutralizing activity and cellular immune response in samples from health care workers who were immunized with two doses of an inactivated virus-based vaccine (CoronaVac) who had or did not have COVID-19 previously. IgA and IgG antibodies directed at the spike protein were analysed in samples of saliva and/or serum by ELISA and/or chemiluminescence assays; the neutralizing activity of serum antibodies against reference strain B, Gamma and Delta SARS-CoV-2 variants were evaluated using a virus neutralization test and SARS-CoV-2 reactive interferon-gamma T-cell were analysed by flow cytometry. CoronaVac was able to induce serum and salivary IgG anti-spike antibodies and IFN-γ producing T cells in most individuals who had recovered from COVID-19 and/or were vaccinated. Virus neutralizing activity was observed against the ancestral strain, with a reduced response against the variants. Vaccinated individuals who had previous COVID-19 presented higher responses than vaccinated individuals for all variables analysed. Our study provides evidence that the CoronaVac vaccine was able to induce the production of specific serum and saliva antibodies, serum virus neutralizing activity and cellular immune response, which were increased in previously COVID-19-infected individuals compared to uninfected individuals.