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.

Baseline Seroprevalence of SARS-CoV-2 Specific Antibodies in Hot Spot Areas of Great Tunis, up to 3 Months Post Disease Onset in Tunisia.

The extent of the SARS-CoV-2 circulation and the COVID-19 epidemic in Tunisia three months after virus circulation was unknown. The aim of this study was to determine the extent of SARS-CoV-2 infection among household contacts of confirmed COVID-19 cases living in Hot spot areas of Great Tunis, Tunisia by estimating the seroprevalence of antibodies anti SARS-CoV-2 and to identify factors associated to seroprevalence at the first stage of the pandemic in order to guide decision making and to constitute a baseline for further longitudinal analysis of protective immunity to SARS-CoV-2. The National Observatory of New and Emerging Diseases (ONMNE), Ministry of Health Tunisia (MoH), with the support of the Office of the World Health Organization Representative in Tunisia and the WHO Regional Office for the Eastern Mediterranean (EMRO)), conducted a household cross-sectional survey on April 2020 in Great Tunis (Tunis, Ariana, Manouba and Ben Arous). The study was based on the WHO seroepidemiological investigation protocol for SARS-CoV-2 infection. SARS-CoV-2 specific antibodies (IgG and IgM) were qualitatively detected using a lateral immunoassay that detect SARS-CoV-2 nucleocapsid protein and administered by the interviewers. The included subjects were confirmed COVID-19 cases and their households contacts resided in hot spot areas (cumulative incidence rate ≥ 10 cases/100,000 inhabitants) of Great Tunis. Results: In total, 1165 subjects were enrolled: 116 confirmed COVID-19 cases (43 active cases and 73 convalescents cases) and 1049 household contacts resided in 291 households. The median age of participants was 39.0 with 31 years' interquartile range (Min = 8 months; Max = 96 years). The sex ratio (M/F) was 0.98. Twenty-nine per cent of participants resided in Tunis. The global crude seroprevalence among household contacts was 2.5% (26/1049); 95% CI 1.6-3.6%, 4.8%; 95% CI 2.3-8.7% in Ariana governorate and 0.3%; 95% CI 0.01%-1.8% in Manouba governorate. In multivariate analysis, the associated factors independently related to seroprevalence were age ≥25 years (aOR = 5.1; 95% CI 1.2-22.0), history of travel outside Tunisia since January 2020 (aOR = 4.6; 95% CI 1.7-12.9), symptomatic illness in the previous four months (aOR = 3.5; 95% CI 1.4-9.0) and governorate of residence (p = 0.02). The low seroprevalence estimated among household contacts in Great Tunis reflect the effect of public health measures early taken (national lockdown, borders closed, remote work), the respect of non-pharmaceutical interventions and the efficacy of COVID-19 contact-tracing and case management at the first stage of the pandemic in Tunisia.

The Prevalence, Genotype Distribution and Risk Factors of Human Papillomavirus in Tunisia: A National-Based Study.

There are limited national population-based studies on HPV genotypes distribution in Tunisia, thus making difficult an assessment of the burden of vaccine-preventable cervical cancer. In this context, we conducted a national survey to determine the HPV prevalence and genotypes distribution and the risk factors for HPV infections in Tunisian women. This is a cross-sectional study performed between December 2012 and December 2014. A liquid-based Pap smear sample was obtained from all women and samples' DNAs were extracted. Only women with betaglobin-positive PCR were further analysed for HPV detection and typing by a nested-PCR of the L1 region followed by next-generation sequencing. A multiple logistic regression model was used for the analysis of associations between the variables. A total of 1517 women were enrolled in this study, and 1229 out of the 1517 cervical samples were positive for the betaglobin control PCR and tested for HPV. Overall HPV infection prevalence was measured to be 7.8% (96/1229), with significant differences between the grand regions, ranging from 2% in the North to 13.1% in Grand Tunis. High-risk HPV genotypes accounted for 5% of the infections. The most prevalent genotypes were HPV 31 (1%), 16 (0.9%), 59 (0.7%). HPV18 was detected only in four cases of the study population. Potential risk factors were living in Grand Tunis region (OR: 7.94 [2.74-22.99]), married status (OR: 2.74 [1.23-6.13]), smoking habit (OR: 2.73 [1.35-5.51]), occupation (OR: 1.81 [1.09-3.01]) and women with multiple sexual partners (OR: 1.91 [1.07-3.39]). These findings underscore the need to evaluate the cost effectiveness of HPV vaccine implementation, contribute to the evidence on the burden of HPV infections, the critical role of sexual behaviour and socioeconomic status, and call for increased support to the preventive program of cervical cancer in Tunisia.

Epidemiologic patterns of hepatitis A infection during the pre-vaccination era: A population-based survey in Tunisia in 2015.

BACKGROUND: In the 1980s, Tunisia was considered a country of high endemicity for hepatitis A virus (HAV). Since 2000, an epidemiologic shift has led to an increased incidence of symptomatic and severe forms of HAV infection. OBJECTIVES: In 2015, we conducted a cross-sectional nationwide household-based hepatitis A virus (HAV) seroprevalence study in the total population regardless of age, sex, or geographic origin using a stratified sampling design to make an overview of the HAV epidemiologic situation in Tunisia before vaccine implementation. RESULTS: A total of 6,322 individuals were enrolled. The HAV prevalence was 78.8%. The anti-HAV IgG seropositivity rate increased from 16% for ages 5-9 years to 45% for ages 10-14 years, 67% for ages 15-19 years, 87% for ages 20-24 years, and >90% for older age groups, which suggested an age at midpoint of population immunity (AMPI) in late adolescence. It was significantly higher in rural areas (P < 10-3) and varied significantly between and within regions (P < 10-4). CONCLUSIONS: In this study, although the overall AMPI suggestsintermediate endemicity, the regional AMPI varies from intermediate to very high endemicity profiles attributable to different socioeconomic determinants and conditions of sanitation and hygiene. In addition, it provides insights for the best decisions in terms of vaccination strategies.

Identification of transmission chains and clusters associated with COVID-19 in Tunisia.

BACKGROUND: The aim of this study was to characterize the transmission chains and clusters of COVID-19 infection in Tunisia. METHODS: All cases were confirmed by Reverse Transcriptase Polymerase Chain Reaction of a nasopharyngeal specimen. Contact tracing is undertaken for all confirmed cases in order to identify close contacts that will be systematically screened and quarantined. Transmission chains were identified based on field investigation, contact tracing, results of screening tests and by assessing all probable mode of transmission and interactions. RESULTS: As of May 18, 2020, 656 cases out of a total of 1043 confirmed cases of Coronavirus disease 2019 belong to 127 transmission chains identified during the epidemic (mean age 42.36 years, Standard deviation 19.56 and sex ratio 0.86). The virus transmission is the most concentrated in the governorate of Tunis (31.5%), Ariana (10.2%) and Ben Arous (10.2%). Virus transmission occurred 50 times (9.72% of secondary transmission events) between two different governorates. A maximum of seven generations of secondary infection was identified, whereas 62% of these secondary infections belong the first generation. A total of 11 "super spreader" cases were identified in this investigation. Four large clusters have been identified. The evolution of secondary cases highlighted two peaks: one in 2nd April and a second in 16 th April whereas imported cases caused local transmission of virus during the early phase of the epidemic. CONCLUSION: Correct contact tracing and early active case finding is useful to identify transmission chains and source of infection in order to contain the widespread transmission in the community.

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.

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.