Introduction: Studies conducted in real-life scenarios on vaccine protection against COVID-19 constitute an important global priority, but one that is currently mostly neglected in low- and middle-income countries such as Angola. Here, we analyze for the first-time vaccine protection against COVID-19 in a real-life scenario after 6 months of implementing a multi-vaccination plan in Angola, providing estimation of odds ratios in vaccinated individuals and vaccine efficacy against infection by SARS-CoV-2 in a period that coincided with the identification of the Omicron variant in the country. Methods: We used a negative test case-control design to assess the effectiveness of vaccination against confirmed SARS-CoV-2 infection. A total of 4.232 vaccinated and unvaccinated individuals with the result of a rapid antigen diagnostic test against SARS-CoV-2 performed from December 27 to 28, 2021 were included in the study. Data were extracted from the Digital Vaccination Record Platform (Rediv) of the Ministry of Health of Angola. All ethical procedures related to the authorization necessary to carry out the study were followed. Statistical analyzes were performed using version 7.5.2.0 of CDC's Epi Info. Frequency distributions and measures of central tendency were used to characterize the study universe. The general and sex-adjusted and age-adjusted odds ratios, were evaluated by comparing the chances of vaccination between cases and controls, and their associated 95% CI, which were calculated using the Mantel-Haenszel stratification method. The risk classification of Axel Kroeger, Piscoya and Alarcon was used to interpret the odds ratio. The Breslow-Day statistic was used to assess the homogeneity of the odds ratios. Vaccine efficacy was calculated using the odds ratio applying the accepted statistical vaccine efficacy formula:(1 − odds ratio) × 100. For all estimates, a P value < 0.05 was considered statistically significant. Results: The population consisted of 63.63% male and 36.37% female. The mean age was 36 years with a standard deviation of 13. 83. Regarding vaccination status, 83.27% of individuals were vaccinated and 16.73% were unvaccinated, with 21.81% positive and 78.19% negative for SARS -CoV-2. The odds of SARS-CoV-2 infection were 0.85 (95% CI 0.70 – 1.03) times lower in vaccinated compared to unvaccinated individuals, with P=0.09. The overall vaccine efficacy (VE) was 15% (95% CI -3 – 30). Conclusion: There was no statistically significant decrease in the chances of SARS-CoV-2 infection in vaccinated versus unvaccinated individuals. However, the overall vaccine efficacy was 15%.
Introduction: Studies conducted in real-life scenarios on vaccine protection against COVID-19 constitute an important global priority, but one that is currently mostly neglected in low- and middle-income countries such as Angola. Here, we analyze for the first-time vaccine protection against COVID-19 in a real-life scenario after 6 months of implementing a multi-vaccination plan in Angola, providing estimation of odds ratios in vaccinated individuals and vaccine efficacy against infection by SARS-CoV-2 in a period that coincided with the identification of the Omicron variant in the country. Methods: We used a negative test case-control design to assess the effectiveness of vaccination against confirmed SARS-CoV-2 infection. A total of 4.232 vaccinated and unvaccinated individuals with the result of a rapid antigen diagnostic test against SARS-CoV-2 performed from December 27 to 28, 2021 were included in the study. Data were extracted from the Digital Vaccination Record Platform (Rediv) of the Ministry of Health of Angola. All ethical procedures related to the authorization necessary to carry out the study were followed. Statistical analyzes were performed using version 7.5.2.0 of CDC's Epi Info. Frequency distributions and measures of central tendency were used to characterize the study universe. The general and sex-adjusted and age-adjusted odds ratios, were evaluated by comparing the chances of vaccination between cases and controls, and their associated 95% CI, which were calculated using the Mantel-Haenszel stratification method. The risk classification of Axel Kroeger, Piscoya and Alarcon was used to interpret the odds ratio. The Breslow-Day statistic was used to assess the homogeneity of the odds ratios. Vaccine efficacy was calculated using the odds ratio applying the accepted statistical vaccine efficacy formula:(1 − odds ratio) × 100. For all estimates, a P value < 0.05 was considered statistically significant. Results: The population consisted of 63.63% male and 36.37% female. The mean age was 36 years with a standard deviation of 13. 83. Regarding vaccination status, 83.27% of individuals were vaccinated and 16.73% were unvaccinated, with 21.81% positive and 78.19% negative for SARS -CoV-2. The odds of SARS-CoV-2 infection were 0.85 (95% CI 0.70 – 1.03) times lower in vaccinated compared to unvaccinated individuals, with P=0.09. The overall vaccine efficacy (VE) was 15% (95% CI -3 – 30). Conclusion: There was no statistically significant decrease in the chances of SARS-CoV-2 infection in vaccinated versus unvaccinated individuals. However, the overall vaccine efficacy was 15%.
Introduction: Studies conducted in real-life scenarios on vaccine protection against COVID-19 constitute an important global priority, but one that is currently mostly neglected in low- and middle-income countries such as Angola. Here, we analyze for the first-time vaccine protection against COVID-19 in a real-life scenario after 6 months of implementing a multi-vaccination plan in Angola. Methods: 4232 vaccinated and unvaccinated individuals with the result of a rapid antigen diagnostic test against SARS-CoV-2 performed from 27 to 28 December 2021 were included in the study. The general and sex-adjusted and age-adjusted odds ratios were evaluated by comparing the chances of vaccination between cases and controls, and their associated 95% CI, which were calculated using the Mantel–Haenszel stratification method. Vaccine efficacy was calculated using the odds ratio applying the accepted statistical vaccine efficacy formula: (1 − odds ratio) × 100. For all estimates, a p-value < 0.05 was considered statistically significant. Results: The odds of SARS-CoV-2 infection were 0.85 (95% CI 0.70–1.03)-times lower in vaccinated compared to unvaccinated individuals, with p = 0.09. The overall vaccine efficacy (VE) was 15% (95% CI −3–30). Conclusion: There was no statistically significant decrease in the chances of SARS-CoV-2 infection in vaccinated versus unvaccinated individuals.
Introduction: Alternative forms of diagnosis that are simpler than NAAT and with faster results (15–30 min) were developed based on the direct detection of SARS-CoV-2 viral proteins in nasal swabs and other respiratory tract secretions using a lateral flow immunoassay also called a rapid diagnostic test of antigen detection. The WHO recommends that these tests have at least a sensitivity of 80% and a specificity of 97% when compared to the reference test, the RT-PCR. We evaluated the performance of the rapid antigen detection test Panbio COVID-19 at a patient triage point at the Luanda General Hospital. Methods: A cross-sectional study of a prospective nature was carried out with the inclusion of 37 suspected symptomatic cases without a previous diagnosis of COVID-19. The database was created and processed in MedCal version 19.6. Sensitivity, specificity, positive and negative predictive value and accuracy are expressed in percentages with the respective 95% confidence intervals determined using a 2x2 table. Qualitative variables were presented in absolute and relative frequency. The McNemar's test was used to calculate the proportion of RAD test results Panbio COVID-19 in relation to the RT –PCR and a bilateral P value < 0.05 calculated based on the cumulative binomial distribution was considered significant. Results: In our study, 26 (70.3%) of the cases were male, and the mean age was 18 years, with a standard deviation of 14.8, with 14 (37.8%) residing in the municipality of Talatona. Regarding the days of evolution of symptoms, 34 (91.9%) had symptoms with one week of evolution. The RAD test Panbio COVID-19 had a sensitivity of 54.5% (CI 95% 23.3 – 83.2) and specificity of 96.1% (CI 95% 80.3 – 99.9). The positive and negative predictive value was 85.7% (95% CI 44.9 – 97.7) and 83.3% (95% CI 72.2– 90.5) respectively. The accuracy of the test was 83.7% (95% CI 67.9 – 93.8). The difference between the prevalence in the test Panbio COVID-19 and in RT-PCR it was 10.8% (95% CI -1.6 – 23.3), not being statistically significant (P=0.22). As for the cycle threshold, 71.4% of the samples that were positive for RAD test Panbio COVID-19 had a cycle threshold ≤ 25. Conclusion: The RAD test Panbio COVID-19 did not meet the minimum accuracy requirements recommended by the WHO. However, the predictive values were considerably high in symptomatic subjects.
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