Factors influencing the immune response over 15 months after SARS-CoV-2 infection: A longitudinal population-wide study in the Faroe Islands.

BACKGROUND: The durability of SARS-CoV-2 antibody response and the resulting immunity to COVID-19 is unclear. OBJECTIVES: To investigate long-term humoral immunity to SARS-CoV-2. METHODS: In this nationwide, longitudinal study, we determined antibody response in 411 patients aged 0-93 years from two waves of infections (March to December 2020) contributing 1063 blood samples. Each individual had blood drawn on 4-5 occasions 1-15 months after disease onset. We measured total anti-SARS-CoV-2 receptor-binding domain (RBD) antibody using a qualitative RBD sandwich ELISA, IgM, IgG and IgA levels using an quantitative in-house ELISA-based assay  and neutralizing antibodies (NAbs) using an in-house ELISA-based pseudoneutralizing assay. IgG subclasses were analyzed in a subset of samples by ELISA-based assay. We used nonlinear models to study the durability of SARS-CoV-2 antibody responses and its influence over time. RESULTS: After 15 months, 94% still had detectable circulating antibodies, mainly the IgG isotype, and 92% had detectable NAbs. The distribution of IgG antibodies varied significantly over time, characterized by a biphasic pattern with an initial decline followed by a plateau after approximately 7 months. However, the NAbs remained relatively stable throughout the period. The strength of the antibody response was influenced by smoking and hospitalization, with lower IgG levels in smokers and higher levels in hospitalized individuals. Antibody stability over time was mainly associated with male sex and older age with higher initial levels but more marked decrease. CONCLUSIONS: The humoral immune response to SARS-CoV-2 infection varies depending on behavioral factors and disease severity, and antibody stability over 15 months was associated with sex and age.

Long COVID in the Long Run-23-Month Follow-up Study of Persistent Symptoms.

Symptoms of long coronavirus disease (COVID) were found in 38% of 170 patients followed for a median of 22.6 months. The most prevalent symptoms were fatigue, affected taste and smell, and difficulties remembering and concentrating. Predictors for long COVID were older age and number of symptoms in the acute phase. Long COVID may take many months, maybe years, to resolve.

Long COVID in the Long Run—23-Month Follow-up Study of Persistent Symptoms

Symptoms of long coronavirus disease (COVID) were found in 38% of 170 patients followed for a median of 22.6 months. The most prevalent symptoms were fatigue, affected taste and smell, and difficulties remembering and concentrating. Predictors for long COVID were older age and number of symptoms in the acute phase. Long COVID may take many months, maybe years, to resolve.

Prevalence of long COVID in a national cohort: longitudinal measures from disease onset until 8 months' follow-up.

OBJECTIVES: Persistence of COVID-19 symptoms in nonhospitalized individuals beyond a few months has not been well characterized. In this longitudinal study from the Faroe Islands, we present prevalence of long COVID in mainly nonhospitalized patients who were followed up for up to 8 months. METHODS: All Faroese individuals with confirmed COVID-19 diagnosis from August to December 2020 were invited to participate in this study (n = 297). Demographic and clinical characteristics and self-reported symptoms were ascertained prospectively using a detailed questionnaire administered at repeated phone interviews. RESULTS: A total of 226 individuals participated at baseline (226/297, 76% participation rate), of whom 170 participants had more than 3 months follow-up. Of these, 39% (n = 67/170, 95% confidence interval [CI] 32-37%) reported persistent symptoms (median [range] 168 [93-231] days) after the acute phase and 8% (n = 14/170, 95% CI 5-13%) reported severe persistent symptoms. The most prevalent symptoms were fatigue (17%) and smell (17%) and taste (14%) dysfunction. Long COVID was more common in people reporting daily medication use (odds ratio 2.34, 95% CI 1.02-5.37). CONCLUSION: Our results show that symptoms may take months to resolve, even among nonhospitalized individuals, with a mild illness in the acute phase. Continued monitoring for long COVID is needed to evaluate the added risk of a potential public health concern.

Long COVID in the Faroe Islands: A Longitudinal Study Among Nonhospitalized Patients.

BACKGROUND: Little is known about long-term recovery from coronavirus disease 2019 (COVID-19) disease, especially in nonhospitalized individuals. In this longitudinal study we present symptoms registered during the acute phase as well as long COVID (ie, long-lasting COVID-19 symptoms) in patients from the Faroe Islands. METHODS: All consecutive patients with confirmed reverse transcription-polymerase chain reaction testing from April to June 2020 were invited to participate in this study for the assessment of long COVID. Demographic and clinical characteristics and self-reported acute and persistent symptoms were assessed using a standardized detailed questionnaire administered at enrollment and at repeated phone interviews in the period 22 April to 16 August. RESULTS: Of the 180 participants (96.3% of the 187 eligible COVID-19 patients), 53.1% reported persistence of at least 1 symptom after a mean of 125 days after symptoms onset, 33.0% reported 1 or 2 symptoms, and 20.1% reported 3 or more symptoms. At the last follow-up, 46.9% were asymptomatic compared with 4.4% during the acute phase. The most prevalent persistent symptoms were fatigue, loss of smell and taste, and arthralgias. CONCLUSIONS: Our results show that it might take months for symptoms to resolve, even among nonhospitalized persons with mild illness course in the acute phase. Continued monitoring for long COVID is needed.

Seroprevalence of SARS-CoV-2-Specific Antibodies among Quarantined Close Contacts of COVID-19 Patients, Faroe Islands, 2020.

Close contacts of coronavirus disease (COVID-19) patients are at high risk for severe acute respiratory syndrome 2 (SARS-CoV-2) infection. We assessed the seroprevalence of SARS-CoV-2-specific antibodies among quarantined close contacts of COVID-19 patients in the Faroe Islands. We invited quarantined close contacts of COVID-19 index patients identified during March 3-April 22, 2020, to participate in this study; 584 (81%) contacts consented and underwent serologic testing. Among the 584 participants, 32 (5.5%) were seropositive for total antibody against SARS-CoV-2. Household and young or elderly contacts had higher risk for seropositivity than other contacts. We found a secondary attack rate of 19.2%. Seroprevalence among close contacts was almost 10-fold higher than among the general population of the Faroe Islands. Regularly testing household close contacts of COVID-19 patients might help track the transmission of SARS-CoV-2.

Epidemiology and Clinical Course of First Wave Coronavirus Disease Cases, Faroe Islands.

The Faroe Islands was one of the first countries in the Western Hemisphere to eliminate coronavirus disease (COVID-19). During the first epidemic wave in the country, 187 cases were reported between March 3 and April 22, 2020. Large-scale testing and thorough contact tracing were implemented early on, along with lockdown measures. Transmission chains were mapped through patient history and knowledge of contact with prior cases. The most common reported COVID-19 symptoms were fever, headache, and cough, but 11.2% of cases were asymptomatic. Among 187 cases, 8 patients were admitted to hospitals but none were admitted to intensive care units and no deaths occurred. Superspreading was evident during the epidemic because most secondary cases were attributed to just 3 infectors. Even with the high incidence rate in early March, the Faroe Islands successfully eliminated the first wave of COVID-19 through the early use of contact tracing, quarantine, social distancing, and large-scale testing.

Seroprevalence of SARS-CoV-2-Specific Antibodies, Faroe Islands.

We conducted a nationwide study of the prevalence of severe acute respiratory syndrome coronavirus 2 infection in the Faroe Islands. Of 1,075 randomly selected participants, 6 (0.6%) tested seropositive for antibodies to the virus. Adjustment for test sensitivity and specificity yielded a 0.7% prevalence. Our findings will help us evaluate our public health response.