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Vaccine effectiveness (VE) studies provide real-world evidence to monitor vaccine performance and inform policy. The WHO Regional Office for the Eastern Mediterranean supported a regional study to assess the VE of COVID-19 vaccines against different clinical outcomes in four countries between June 2021 and August 2023. Health worker cohort studies were conducted in 2707 health workers in Egypt and Pakistan, of whom 171 experienced symptomatic laboratory-confirmed SARS-CoV-2 infection. Test-negative design case–control studies were conducted in Iran and Jordan in 4017 severe acute respiratory infection (SARI) patients (2347 controls and 1670 cases) during the Omicron variant dominant period. VE estimates were calculated for each study and pooled by study design for several vaccine types (BBIBP-CorV, AZD1222, BNT162b2, and mRNA-1273, among others). Among health workers, VE against symptomatic infection of a complete primary series could only be computed compared to partial vaccination, suggesting a benefit of providing an additional dose of mRNA vaccines (VE: 88.9%, 95%CI: 15.3–98.6%), while results were inconclusive for other vaccine products. Among SARI patients, VE against hospitalization of a complete primary series with any vaccine compared to non-vaccinated was 20.9% (95%CI: 4.5–34.5%). Effectiveness estimates for individual vaccines, booster doses, and secondary outcomes (intensive care unit admission and death) were inconclusive. Future VE studies will need to address challenges in both design and analysis when conducted late during a pandemic and will be able to utilize the strengthened capacities in countries.

Objective A cohort study was conducted with the support of the WHO, where a standardized WHO protocol was followed to assess vaccine effectiveness (VE) against symptomatic RT‒PCR confirmed SARS‒CoV-2 infection among hospital health workers (HWs) eligible for vaccination at Al-Azhar University hospitals. Methods A WHO-supported cohort study was conducted from July 2022 through September 2023 and included 1249 HWs who were randomly selected and followed up biweekly for one year. At enrollment, nasopharyngeal (NP) and blood samples were collected from each participant and evaluated to detect SARS-CoV-2 RNA via a real-time PCR assay (QIAGEN) and for the quantitative detection of SARS-CoV-2 binding antibodies via the Roche Elecsys Anti-SARS-CoV-2 S immunoassay (Roche Diagnostics, GmbH, Germany). During follow-up, NP samples were collected from anyone who developed symptoms consistent with the WHO definition of suspected cases of SARS-CoV-2 infection. Results At enrollment, SARS-CoV-2 RNA was detected in 119/1235 (9.6%) HWs and 89% of the participants with positive RNA were asymptomatic. COVID-19-binding antibodies were detected among 1245/1248 (99.8%) HWs, and 53.2% of them had titers > 2500 U/mL, regardless of vaccination status. During follow-up, 232 participants had COVID-19 symptoms, but only 108 provided NP samples, and 18 (16.7%) of them were positive for SARS-CoV-2 RNA. No hospitalization or mortality was recordedat enrollment or during the follow-up period. The cumulative incidence of COVID-19 infection was higher among HWs with incomplete vaccination compared to unvaccinated, fully vaccinated, or those who received booster doses ( P  = 0.025). There was no significant difference in VE among HWs who were fully vaccinated or had booster doses compared with unvaccinated HWs, with adjusted VE values of 68% (95% CI -28–92%) and 64% (95% CI -170–95%), respectively ( P  = 0.106 and 0.318 respectively). The adjusted VE increased to 89% (95% CI -33–99%) among HWs with hybrid immunity compared with those who were unvaccinated with a previous COVID-19 infection ( P  = 0.082). Conclusion This study indicates that VE against symptomatic lab-confirmed SARS-CoV-2 infection was quite high with over 60% protection and was higher among HWs with hybrid immunity (immunity due to a combination of previous infection and vaccination) compared to unvaccinated HWs with previous COVID-19 infection. The findings also highlight the importance of completing the primary vaccination series against COVID-19. This study reveals a high rate of asymptomatic COVID-19, a lower rate of confirmed cases, who showed marked decrease in hospitalization and fatality rates. Real-world VE studies are essential to address several unresolved issues, such as the appropriate number of booster doses and the longevity of protection.

The presence of isolated anti-HBc (IAHBc) is not rare, being found in up to 10-20% of the population in endemic countries, i.e., China and Korea, and in 0.4-1.7% of blood donors in low-prevalence areas i.e., Europe and the United States of America.1 IAHBc tends to be more common in males and increases with age.2 The prevalence rises in individuals with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) coinfection. Clinical management of IAHBc in different risk groups a.Immunocompromised patients Hepatitis B reactivation risk in patients with IAHBc should be stratified according to type of immunosuppressant drug and underlying disease into high-, moderate- and low- risk groups.3'4 The risk of reactivation is >10% in the high-risk group, 1-10% in the moderate risk group and <1% in the low-risk group. No evidence of hepatitis B virus reactivation in patients with resolved infection treated with direct-acting antivirals for hepatitis C in a large real-world cohort.