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Mziou E, Hchaichi A, Letaief H, Dhaouadi S, Safer M, Talmoudi K, Mhadhbi R, Elmili N, Bouabid L, Derouiche S, Bougatef S, Bellali H, Bouafif Ép Ben Alaya N. Vaccine effectiveness against COVID-19: A test negative case-control study in Tunisia, August 2021. Vaccine 2024; 42:1738-1744. [PMID: 38365483 DOI: 10.1016/j.vaccine.2024.02.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 01/21/2024] [Accepted: 02/07/2024] [Indexed: 02/18/2024]
Abstract
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.
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Affiliation(s)
- Emna Mziou
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia.
| | - Aicha Hchaichi
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia; Faculty of Medicine of Tunis, University Tunis El Manar, Tunisia
| | - Hejer Letaief
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia; Faculty of Medicine of Tunis, University Tunis El Manar, Tunisia
| | - Sonia Dhaouadi
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia; Faculty of Medicine of Tunis, University Tunis El Manar, Tunisia
| | - Mouna Safer
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia; Faculty of Medicine of Tunis, University Tunis El Manar, Tunisia
| | - Khouloud Talmoudi
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia; Faculty of Medicine of Tunis, University Tunis El Manar, Tunisia
| | - Rim Mhadhbi
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia
| | - Nawel Elmili
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia
| | - Leila Bouabid
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia
| | - Sondes Derouiche
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia
| | - Souha Bougatef
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia
| | - Hedia Bellali
- Faculty of Medicine of Tunis, University Tunis El Manar, Tunisia
| | - Nissaf Bouafif Ép Ben Alaya
- National Observatory of New and Emerging Diseases, Ministry of Health, Tunisia; Faculty of Medicine of Tunis, University Tunis El Manar, Tunisia
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Safer M, Letaief H, Hechaichi A, Harizi C, Dhaouadi S, Bouabid L, Darouiche S, Gharbi D, Elmili N, Ben Salah H, Hammami M, Talmoudi K, Moussa R, Charaa N, Termiz H, Ltaief F, Tounekti H, Makhlouf M, Belguith Sriha A, Ben Fredj M, Khalfallah S, Jabrane H, Mchirgui S, Amich C, Dabghi R, Anez Z, Abdelkader L, Mhamdi M, Ouerfeli N, Zoghlami S, Bougatef S, Chahed MK, Bouafif Ben Alaya N. Identification of transmission chains and clusters associated with COVID-19 in Tunisia. BMC Infect Dis 2021; 21:453. [PMID: 34011266 PMCID: PMC8132040 DOI: 10.1186/s12879-021-06107-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 04/22/2021] [Indexed: 12/12/2022] Open
Abstract
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.
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Affiliation(s)
- Mouna Safer
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia.
- Cardio Vascular Disease Epidemiology and Prevention Research Laboratory, Faculty of Medicine, University of Tunis El Manar, Tunis, Tunisia.
| | - Hejer Letaief
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
- Cardio Vascular Disease Epidemiology and Prevention Research Laboratory, Faculty of Medicine, University of Tunis El Manar, Tunis, Tunisia
| | - Aicha Hechaichi
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
- Cardio Vascular Disease Epidemiology and Prevention Research Laboratory, Faculty of Medicine, University of Tunis El Manar, Tunis, Tunisia
| | - Chahida Harizi
- Department of Epidemiology and Statistics, Abderrahman Mami Hospital, Ariana, Tunisia
| | - Sonia Dhaouadi
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Leila Bouabid
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Sondes Darouiche
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Donia Gharbi
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Nawel Elmili
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Hamida Ben Salah
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Mongi Hammami
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Khouloud Talmoudi
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
| | - Rim Moussa
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Nejib Charaa
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Hasna Termiz
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Fethi Ltaief
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Habib Tounekti
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | | | - Asma Belguith Sriha
- Department of Community and Preventive Medicine Faculty of Medicine, University of Monastir Tunisia, Tunis, Tunisia
| | - Manel Ben Fredj
- Department of Community and Preventive Medicine Faculty of Medicine, University of Monastir Tunisia, Tunis, Tunisia
| | | | - Houcine Jabrane
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Selma Mchirgui
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Chedli Amich
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Radhia Dabghi
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Zid Anez
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | | | - Moncef Mhamdi
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Nabil Ouerfeli
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Salah Zoghlami
- Public Health Surveillance Regional Departments, Tunis, Tunisia
| | - Souha Bougatef
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
- Cardio Vascular Disease Epidemiology and Prevention Research Laboratory, Faculty of Medicine, University of Tunis El Manar, Tunis, Tunisia
| | - Mohamed Kouni Chahed
- Department of Epidemiology and Public Health, Faculty of Medicine of Tunis, Tunis El-Manar University, Tunis, Tunisia
| | - Nissaf Bouafif Ben Alaya
- National Observatory of New and Emerging Diseases, Ministry Of Health, Tunis, Tunisia
- Cardio Vascular Disease Epidemiology and Prevention Research Laboratory, Faculty of Medicine, University of Tunis El Manar, Tunis, Tunisia
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