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.

Epidemiological 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 epidemiological shift has led to an increased incidence of symptomatic and severe forms of HAV infection.

OBJECTIVE

In 2015, we conducted a cross-sectional nationwide household-based HAV seroprevalence study in the total population regardless of age, sex, or geographical origin using a stratified sampling design in order to make an overview of the HAV epidemiological situation in Tunisia before vaccine implementation.

RESULTS

A total of 6322 individuals were enrolled. The HAV prevalence was 78.8%. The anti-HAV IgG seropositivity rate increases from 16% for ages 5-9 years to 45% for ages 10-14, 67% for ages 15-19, 87% for ages 20-24, and >90% for older age groups, which suggests 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 suggests intermediate endemicity, the regional AMPI varies from intermediate to very high endemicity profiles attributable to different socio-economic determinants and conditions of sanitation and hygiene. Also it provides insights for the best decisions in terms of vaccinations 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.

FRI0651-HPR A RANDOMIZED PROSPECTIVE OPEN-LABEL CONTROLLED TRIAL COMPARING THE PERFORMANCE OF A CONNECTED MONITORING INTERFACE IN PATIENTS WITH RHEUMATOID ARTHRITIS VERSUS PHYSICAL ROUTINE MONITORING

Background:

Telemedicine has found wider application in chronic diseases for encouraging tight home-monitoring in order to improve patients’ outcome (Smolen et al. 2017).

In previous studies, a high feasibility and high patient-satisfaction rate was found as well as the evidence for a superior or equal effectiveness of telemedicine compared to the standard face-to-face approach, however the results were weakened by some methodological biases and wide heterogeneity of interventions, thus preventing to draw definitive conclusions (Piga et al. 2017; Najm, Gossec, et al. 2019).

Objectives:

In rheumatoid arthritis (RA), telemedicine may allow a tight control of disease activity while reducing hospital visits. We developed a smartphone application connected with a physician’s interface to monitor RA patients. We aimed to assess the performance of this e-Health solution in comparison with routine practice in the management of patients with RA.

Methods:

A 6-month pragmatic, randomized, controlled, prospective, clinical trial was conducted in RA patients with high to moderate disease activity starting a new Disease Modifying Anti-Rheumatic Drug (DMARD) therapy. Two groups were established: “connected monitoring” and “conventional monitoring”. The primary outcome was the number of physical visits between baseline and 6 months. Secondary outcomes included adherence, satisfaction, changes in clinical, functional, and health status scores (SF-12).

Results:

Of the 94 randomized patients, 89 completed study: 44 in the “conventional monitoring” arm and 45 in the “connected monitoring” arm. The total number of physical visits between baseline and 6 month was significantly lower in the “connected monitoring” group (0.42 ± 0.58 versus 1.93 ± 0.55; p<0.05). No differences between groups were observed in the clinical and functional scores. A better quality of life for SF-12 subscores (Role-Physical, Social-Functioning and Role-Emotional) were found in the “connected monitoring” group.

Conclusion:

According to our results, a connected monitoring reduces the number of physical visits while maintaining a tight control of disease activity and improving quality of life in patients with RA starting a new treatment.

References:

[1] Najm, Aurelie, Laure Gossec, Catherine Weill, David Benoist, Francis Berenbaum, and Elena Nikiphorou. 2019. “Mobile Health Apps for Self-Management of Rheumatic and Musculoskeletal Diseases: Systematic Literature Review.”JMIR MHealth and UHealth7 (11): e14730.https://doi.org/10.2196/14730.

[2] Piga, Matteo, Ignazio Cangemi, Alessandro Mathieu, and Alberto Cauli. 2017. “Telemedicine for Patients with Rheumatic Diseases: Systematic Review and Proposal for Research Agenda.”Seminars in Arthritis and Rheumatism47 (1): 121–28.https://doi.org/10.1016/j.semarthrit.2017.03.014.

[3] Smolen, Josef S, Robert Landewe, Johannes Bijlsma, Gerd Burmester, Katerina Chatzidionysiou, Maxime Dougados, Jackie Nam, et al. 2017. “EULAR Recommendations for the Management of Rheumatoid Arthritis with Synthetic and Biological Disease-Modifying Antirheumatic Drugs: 2016 Update.”Annals of the Rheumatic Diseases76 (6): 960–77.https://doi.org/10.1136/annrheumdis-2016-210715.

Disclosure of Interests:

None declared

Prevalence and risk factors of hepatitis B in Tunisia

Background

Hepatitis B virus (HBV) infection is a major public health problem. Data related to epidemiology, distributions and outcomes of VHB infections in Tunisia remains scarce. This work aimed to study the prevalence of HBV infections and their distribution as well as the main risk factors associated to HBV infection.

Methods

Our study was a cross-sectional household- based study carried out among a representative sample of 22 275 from January 2014 to December 2015. Sampling was based on the National Census of 2014. For data collection, questionnaires were administrated by trained investigator and blood samples were sent to the Reference laboratory for analysis of HBV markers.

Results

Among 21720 surveyed subjects, 19663 subjects had a laboratory tests and the serological results reached to 19155. Overall prevalence of HBs Ag was 1.7% [1.6-1.9]. Prevalence of HBsAg was significantly higher in men (2.1% against 1.4%; p &lt; 10-3), in age group more than 20 years (2.1% against 0.1% p ≪10-3) and in the Central region (2.3%; p &lt; 10-3). Among the associated risk factors in univariate analysis were chronic dialysis, dental care, surgical intervention, hospitalization, traditional circumcision, scarification and multiple sexual partners. Multivariate analysis showed that male gender, age over 20 years, center and south regions, hospital follow-up of a chronic pathology and having a family member chronic carrier of HBs Ag were the associated risk factors of HBV infection and vaccination was the only protective factor.

Conclusions

Our study allowed to have a clear estimate of the national prevalence of HBsAg and to classify Tunisia as a country of low endemicity of Hepatitis B. This decline is mainly due to the introduction of vaccination since 1995 and the improvement of the health system. However, more efforts should be paid to reduce nosocomial transmission and traditional high-risk behaviors.

Key messages

Tunisia has become a country of low endemicity for hepatitis B. This was a result to the introduction of vaccination since 1995.

Impact of hepatitis B vaccine in Tunisia 20 years after its introduction

Introduction

Vaccination against hepatitis B represents the most effective preventive measure to reduce the global impact of this infection. In Tunisia hepatitis B vaccination was introduced for health professionals in 1992 and for the general population in 1995. The objectives of this study were to evaluate the impact of vaccination twenty years after its introduction.

Methods

It was a descriptive study of data provided by the national survey of prevalence of Hepatitis B in Tunisia, which was a household-based study conducted in 2015. Blood samples sent to the reference laboratory to test markers of hepatitis B virus infection. The Vaccine effectiveness rate was calculated using the following formula: VE = 1 - Odds-ratio (OR), where OR = ratio of odds of being vaccinated among subjects with positive HBsAg test results to the odds of being vaccinated among subjects with negative HBsAg test results.

Results

Approximately a quarter of our population reported having been vaccinated against HBV, a coverage rate of 26.9%. Among subjects above 20 years of age, this rate was 85.3%. Besides, 83.7% of vaccinated subjects had received the three required doses of the HBV vaccine. Analysis of vaccination status by great regions of the country showed that the vaccination coverage rate was higher in the southern region. Regarding HBsAg prevalence, the rate was significantly higher among unvaccinated subjects 0.3% vs 2.2% in those vaccinated (OR = 0.11 [0.07-0.18]). We found that among vaccinated subjects, the serologic response rate at vaccination was only 63.2% which represented 16.2% of the total population. The vaccine effectiveness indicated that vaccination reduced by 88.6% the risk of HBV infection.

Conclusions

These results demonstrate that vaccination against hepatitis B introduced in the national immunization schedule since 1995 has reduced the infection although the vaccination coverage rate remains below 90%.

Key messages

Importance of vaccination that reduced by 88.6% the risk of HBV infection. More effort required to raise awareness about vaccination against HBV.

Human papillomavirus infections and cervical cancer screening in Tunisian women

Background

Human papillomavirus (HPV) infections are a significant public health problem with global estimations over 520 000 new cases and 274 000 deaths due to cervical cancer. In Tunisia, cervical cancer is the third cause of cancer in women but only a few prevalence studies conducted in specific populations are available. The present study aims to estimate the national prevalence of HPV infection and cervical cancer testing among Tunisian women.

Methods

We conducted a population-based cross-sectional study in 2014. We included all sexually active women aged 18 years and older, present in primary health care centers the day of the study. Data collection was based on a standardized questionnaire including socio-demographic data, high-risk behaviors and previous cervical screening. HPV detection and typing was only done for betaglobin positive PCR-test. Ethical considerations were respected.

Results

The total number of surveyed women was 1494 and the overall prevalence of HPV infection was 7.5% IC95% [5.9%-9.0%]. The most common genotypes were HPV6 (21.9%) and HPV16 (11.5%). Prevalence of high-risk HPV was higher than low-risk HPV; 4.8% IC95% [3.7%-6.2%] and 3.8% IC95% [2.8%-4.8%] respectively. The prevalence of previous cervical screening was 36.6% (95% CI [34.3%-39.2%]). This rate was significantly associated with age (p &lt; 10-3); from 13.9% among those &lt;30 years to 49.3% among those ≥ 50 years.

Conclusions

Our survey provides an important overview of the current situation of HPV infection among Tunisian women. National prevalence of HPV infection was 7.5% but only 36.6% of women had a previous cervical cancer screening. This coverage remains poor, thus the need of targeted education and encouraging strategies to reduce cervical cancer burden in Tunisia.

Key messages

National prevalence of HPV infection is not negligeable in Tunisia, especially high risk HPV infections. Cervical screening is still low among Tunisian women, hence the need for education targeted to this population.