Efficacy of COVID-19 Vaccines against Mortality among COVID-19 Cases of Indore, Central India

Background: Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-COV2) virus is being used since January 2021 in India. Current data shows that the vaccines are effective against coronavirus disease 2019 (COVID-19) related morbidity and mortality. Vaccine efficacy in fully vaccinated may decrease over time. Materials and methods: Retrospective study was done to assess vaccine efficacy against COVID-19 pneumonia related deaths in a tertiary COVID-19 care hospital in Central India. The vaccine efficacy was assessed in the patients with respect to age, gender, and comorbidity and since they received 2nd dose of the vaccine, the study also investigated the waning effectiveness over time leading to mortality. Results: Vaccine effectiveness against COVID-19 mortality did not peak in the early weeks post receiving the second dose (12.5% mortality in 1st month) but then it increased by the 5th month (7.4% mortality). After the 5th month, vaccine effectiveness decreased (11.9% mortality). Waning of vaccine effectiveness causing mortality was greater in the elderly >= 60 years (18.2%) than in patients <60 years (5.4%). Fully vaccinated males had higher mortality than females. A greater reduction in vaccine efficacy was observed in persons with comorbidities (14.1% mortality) than in noncomorbid (3.4% mortality). On comparing all patients with comorbidity, there was lower mortality in patients who received a full dose of vaccination (14.1%) than those who didn't (22.7%). Fully vaccinated elderly >= 60 years (18.2%) had lesser mortality than those who were not vaccinated (36.4%). Conclusion: Waning of vaccine effectiveness and related death is seen against COVID-19 after the 5th-month post second dose of the COVID-19 vaccine. Greater mortality is noted in the elderly, males, and patients with comorbidities. Fully vaccinated elderly and patients with comorbidities had a lower mortality rate than those who were not vaccinated.