Author

A. Kaleeckal

3 papers indexed here

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Open access Sep 2026

Two Versus One COVID-19 Vaccine Dose After Prior SARS-CoV-2 Infection: A Nationwide Retrospective Cohort Study

Abstract Background Immune protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) varies by prior infection and vaccination history. This study evaluated whether 2 coronavirus disease (COVID-19) vaccine doses after prior infection provide additional protection compared with a single dose. Metho...

H. Chemaitelly, H. Ayoub, Peter V. Coyle et al. · Open Forum Infectious Diseas... · 0 citations

Open access Aug 2026

Evaluating COVID-19 vaccine effectiveness across epidemiologic designs: test-negative case-control versus retrospective cohort analyses in a nationwide study

Abstract Background Observational studies are central to assessing vaccine effectiveness and informing public health policy. The two most common designs are test-negative case-control and cohort studies, yet direct comparisons of their performance using the same population, data sources, and analytic strategies remain...

Layan Sukik, Pradipta Paul, H. Ayoub et al. · International Journal of Epi... · 0 citations

Open access Jul 2026

Healthy vaccinee effect did not bias COVID-19 vaccine effectiveness estimates

It is shown that vaccine effectiveness against infection and severe, critical, or fatal COVID-19 remained consistent across matching strategies, despite differences in non-COVID-19 mortality, highlighting the importance of using specific outcomes in vaccine effectiveness studies.

H. Chemaitelly, H. Ayoub, Peter V. Coyle et al. · Communications Health · 0 citations