Vaccine effectiveness against COVID-19: A test negative case-control study in Tunisia, August 2021.

BACKGROUND: In response to the COVID-19 pandemic, multiple vaccines to protect against COVID-19 disease have been developed rapidly. Precise estimates of vaccine effectiveness (VE) vary according to studies design, outcomes measured and circulating variants. The aim of this study was to evaluate the anti-covid-19 vaccine effectiveness in Tunisia. METHODS: We conducted a matched case-control study from 2nd to 15th August 2021. Cases and controls were subjects over 60 years of age, selected from the National testing database, regardless vaccine status. A standardized questionnaire was administered for cases and controls to collect information about vaccination status. For cases, vaccination status was defined based on the number of doses received before becoming ill and excludes doses received during the previous two weeks. For matched controls, a reference date based on the case's date of illness onset was defined in order to look at the control's vaccination status before its corresponding case became ill. The odds-ratio was calculated using simple conditional logistic regression. The VE (95 % confidence intervals) was calculated as (1 - odds ratio for vaccination) × 100 %. RESULTS: A sample of 977 matched peers for age and Gender, were included between August 2, and August 15, 2021. The overall vaccine effectiveness (VE) was 70 % [95 % CI 62.8-75.8 %]. Among our sample, 68.1 % of the male population and 56.4 % of the female population were vaccinated with a VE of 73 % [95 % CI 62.9-80.3 %] and 67 % [95 % CI 55.8-75.3 %] respectively, regardless vaccine scheme (complete or incomplete). VE was higher for the age group [60-70 years[ (72.3 % [95 % CI 62.8-79.3 %]). VE was 77.6 % [95 % CI 70.9-82.8 %] to prevent both symptomatic and asymptomatic forms of the disease. Moreover, in prevention from severe forms (treated with oxygen-therapy or admission to an Intensive-care-unit) VE was 86.6 % [95 % CI 75.6-92.7 %] and 98.4 % [95 % CI [79.2-99.8 %] in prevention from COVID-19 deaths with a complete anti-Covid vaccination scheme. CONCLUSION: The results of our study showed that the anti-Covid-19 vaccines used in Tunisia are efficient to prevent both SARS-COV-2 infections and severe forms related to the disease. This study provided important data on the performance of vaccines in real-world settings that guide decisions about vaccine sustained use.

Characteristics and prognostic factors of COVID-19 among infected cases: a nationwide Tunisian analysis.

BACKGROUND: The outbreak of coronavirus disease (COVID-19) continues to constitute an international public health concern. Few data are available on the duration and prognostic factors of the disease. We aimed to study the recovery time among a Tunisian cohort of COVID-19 confirmed patients and identify the prognostic factors. METHODS: A retrospective, nationwide study was conducted from March 2 to May 8, 2020, recruiting all patients who were diagnosed with COVID-19, by RT-PCR methods, in Tunisia. Data were collected via phone call interview. Kaplan-Meir Methods and Cox proportional hazards regression models were, respectively, used to study the recovery time and estimate its prognostic factors. RESULTS: One thousand and thirty patients with COVID-19 (aged 43.2 ± 18.2 years, 526 female (51.1%)) were enrolled. Among them 141 (14.8%) were healthcare professionals. Out of 173 patients (17.8%) admitted to the hospital, 47 were admitted in an intensive care unit. Among 827 patients who didn't require specialized care, 55.5% were self-isolated at home, while the rest were in specialized centers. Six hundred and two patients were symptomatic. A total of 634 (61.6%) patients have recovered and 45 (4.4%) patients died. The median duration of illness was estimated to be 31 days (95% CI: [29-32]). Older age (HR = 0.66, CI:[0.46-0.96], P = 0.031) and symptoms (HR = 0.61, CI:[0.43-0.81], P = 0.021) were independently associated with a delay in recovery time. Being a healthcare professional (HR = 1.52, CI: [1.10-2.08], P = 0.011) and patients in home isolation compared to isolation centers (HR = 2.99, CI: [1.85-4.83], P < 10¯3) were independently associated with faster recovery time. CONCLUSION: The duration of illness was estimated to be 1 month. However, this long estimated duration of illness may not equate to infectiousness. A particular attention must to be paid to elderly and symptomatic patients with closer monitoring.

Characteristics, onset, and evolution of neurological symptoms in patients with COVID-19.

BACKGROUND: A wide range of neurological manifestations has been described in COVID-19. METHODS: In this nationwide retrospective observational study, patients in Tunisia diagnosed with COVID-19 between the 2nd of March and the 16th of May 2020 were contacted by telephone. We collected demographic and clinical data and specified characteristics and evolution of main neurological symptoms. RESULTS: Of 1034 confirmed COVID-19 patients, 646 were included (mean age 42.17 years old) and 466 (72.1%) had neurological symptoms. Neurological symptoms were isolated 22.7% (n = 106). Headache was the most frequent neurological symptom (n = 279, 41.1%): mainly frontotemporal (n = 143, 51.1%) and mild or moderate (n = 165, 59.1%). When associated with fever (n = 143, 51.3%), headache was more likely to be severe and present at onset. Recovery was reported in 83.2%. Smell and taste impairment were found in 37.9% (n = 245) and 36.8% (n = 238) respectively. Among them, 65.3% (156/239) were anosmic and 63.2% (146/231) were ageusic. A complete improvement was found in 72.1% (174/240) of smell impairment and in 76.8% (179/233) of taste impairment. Myalgia (n = 241, 37.3%) and sleep disturbances (n = 241, 37.3%) were also frequent. Imported cases had more neurological symptoms (p = 0.001). In 14.5%, neurological symptoms preceded the respiratory signs (RS). RS were associated with more frequent (p = 0.006) and numerous (p < 0.001) neurological symptoms. CONCLUSIONS: Neurological symptoms in COVID-19 are frequent, can be isolated and present at onset. A total recovery is the most recorded outcome. RS are predictive of neurological symptoms. Studies in to virus and host genetics should be considered to understand the different phenotypes.

Estimating transmission dynamics and serial interval of the first wave of COVID-19 infections under different control measures: a statistical analysis in Tunisia from February 29 to May 5, 2020.

BACKGROUND: Describing transmission dynamics of the outbreak and impact of intervention measures are critical to planning responses to future outbreaks and providing timely information to guide policy makers decision. We estimate serial interval (SI) and temporal reproduction number (Rt) of SARS-CoV-2 in Tunisia. METHODS: We collected data of investigations and contact tracing between March 1, 2020 and May 5, 2020 as well as illness onset data during the period February 29-May 5, 2020 from National Observatory of New and Emerging Diseases of Tunisia. Maximum likelihood (ML) approach is used to estimate dynamics of Rt. RESULTS: Four hundred ninety-one of infector-infectee pairs were involved, with 14.46% reported pre-symptomatic transmission. SI follows Gamma distribution with mean 5.30 days [95% Confidence Interval (CI) 4.66-5.95] and standard deviation 0.26 [95% CI 0.23-0.30]. Also, we estimated large changes in Rt in response to the combined lockdown interventions. The Rt moves from 3.18 [95% Credible Interval (CrI) 2.73-3.69] to 1.77 [95% CrI 1.49-2.08] with curfew prevention measure, and under the epidemic threshold (0.89 [95% CrI 0.84-0.94]) by national lockdown measure. CONCLUSIONS: Overall, our findings highlight contribution of interventions to interrupt transmission of SARS-CoV-2 in Tunisia.