ABSTRACT
Introduction In Lebanon, the nationwide vaccination against COVID-19 was launched in February-2021 using Pfizer-BioNTech vaccine and prioritizing elderly, persons with comorbidities and healthcare workers. Our study aims to estimate the post-introduction vaccine effectiveness (VE) of Pfizer-BioNTech in preventing COVID-19 hospitalization among [≥]75 years in Lebanon. Methods A case-control study design was used. Cases were Lebanese, [≥]75 years and hospitalized with positive PCR result during April-May 2021. Cases were randomly selected from the COVID-19 database of the Epidemiological Surveillance Unit(ESU) at the Ministry of Public Health(MOPH). Each case was matched by age and locality to 2 controls. Controls were hospitalized, non-COVID-19 patients with negative PCR result, randomly selected from the MOPH hospital admission database. VE was calculated for fully and partially vaccinated, using multivariate conditional logistic regression analyses. Results 345 cases and 814 controls were recruited. Half were females, with a mean age of 83 years. 14 cases(5%) and 143 controls(22%) were fully vaccinated. Univariate analysis showed significant association with: gender, month of confirmation/admission, general health, chronic medical conditions, main income source and living arrangement. After adjusting for month of admission and gender, multivariate analysis yielded a VE of 82% (95%CI = 69%-90%) against COVID-19 associated hospitalization for those fully vaccinated and 53% (95%CI = 23%-71%) for those partially vaccinated (<14 days of first or within 14 days of second dose). Conclusions Our study showed that Pfizer-BioNTech vaccine is effective in reducing risk for COVID-19-associated hospitalization in Lebanese elderly([≥]75 years). Additional studies are warranted to explore vaccine effectiveness in reducing hospitalization in younger age groups, as well as in reducing covid-19 infections.