COVID-19 vaccine effectiveness and SARS-CoV-2 variants in Nepal: Test-negative case-control study and genetic sequencing (COVVAR Nepal)

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Background Few data are available on the genetic variants of SARS-CoV-2 which circulated in Nepal and the effectiveness of various COVID-19 vaccines used in the country. In this study, we estimated the effectiveness of different COVID-19 vaccines against laboratory-confirmed COVID-19 during the third wave of the COVID-19 pandemic and also identified circulating SARS-CoV-2 variants. Methods We conducted a hospital-based, prospective test-negative case–control study at Patan Hospital, Kathmandu. All patients >18 years of age presenting to Patan Hospital with COVID-19-like symptoms who received a COVID-19 antigen/PCR test were enrolled. Positive SARS-CoV-2 samples were sequenced to identify circulating variants and vaccine effectiveness against laboratory-confirmed COVID-19 disease was calculated using logistic regression. Results A total of 285 participants were enrolled between November 2021 and July 2023, with 157 testing SARS-CoV-2 positive. All the positive samples were of the omicron sub lineages. Six were excluded due to conflicting PCR and antigen test results. Partial or full immunization with COVID-19 vaccines did not show any protective effect against mild symptomatic infection. Vaccine effectiveness(VE) (95% CI) was 62%(-303,96) against severe hospitalized cases (p=0.42), whereas VE (95% CI) was 86%(42,97) in non-severe hospitalized cases (p=0.007). Participants who were hospitalized were less likely to have been vaccinated than non-hospitalized cases (odds ratio 0.07). Conclusion As expected we found that Covid-19 vaccines did not protect against mild symptomatic infections in the Omicron era but were associated with reduced odds of hospitalization.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.