Effect of vaccination against Covid-19 one year after its introduction in Brazil

Abstract

Background Worldwide, several efforts have been made to develop, distribute and administer safe and effective vaccines to reduce morbidity and mortality and control the Covid-19 pandemic. This study aimed to analyze the effect of vaccination against Covid-19, one year after its introduction in Brazil. Methods An ecological study that analyzed the general effect of vaccination against Covid-19 on disease morbidity and mortality indicators among the Brazilian population aged 18 years or older per epidemiological week (EW), comparing the pre and postvaccination period. Morbidity and mortality indicators were calculated from secondary databases (hospitalization rate, severity, case fatality rate and mortality) and vaccination coverage by age groups (18 to 59 years and 60 years or older). Morbimortality trends were estimated using the JoinPoint model and their association with vaccine coverage using the Poisson model. Results The average weekly percentage change (AWPC) of morbidity and mortality indicators reduced after the introduction of Covid-19 vaccination: hospitalization rate (from 15.3% to -6.0%), severity (from 0.4% to -0.2%), case fatality rate (from 0.3% to -0.2%) and mortality (from 20.5% to -4.3%). The following indicators were inversely associated with the increase in vaccine coverage against Covid-19: hospitalization (IRR: 0.974), mortality (IRR: 0.975) and lethality for people aged 60 years or older (IRR: 0.997). Conclusions In spite of the three epidemic waves and the circulation of variants of concern, the general effect of vaccination against Covid-19 in reducing the trend of morbidity and mortality from the disease in Brazil was demonstrated. These findings contribute to a better understanding of the mass vaccination program against Covid-19 and may inform future public health policies.

COVID-19 inpatient mortality in Brazil from 2020 to 2022: a cross-sectional overview study based on secondary data

“…Therefore, our ndings are compatible with those of other studies that have shown that COVID-19 vaccination is associated with a signi cant reduction in hospitalization and inpatient mortality rates. Here, we underline two Brazilian studies that found a signi cant reduction in severe COVID-19 cases, hospitalizations and deaths of elderly individuals after vaccination when it was still restricted to more vulnerable groups, thus producing important declines in relative mortality compared to younger individuals (23,35), and another study that provided evidence of the effectiveness of COVID-19 vaccination, including during the Omicron wave (19). In contrast to Liu et al (17), we opted for not considering the vaccination data available in SIVEP-Gripe at the individual level, owing to its questionable reliability, and indirectly looking at overall vaccination effects through relevant periods over time.…”

“…There is also some evidence that hospitals perform better in contexts in which the prevalence of COVID-19 is lower (7,13). Furthermore, vaccination coverage and learning on how to care for COVID-19 cases impacted, over time, the occurrence of hospitalizations, the pro le of patients hospitalized and healthcare outcomes (11,(18)(19)(20)(21)(22)(23). In Brazil, a relevant aspect not yet explored was the variation in COVID-19 inpatient mortality across categories of hospitals combining ownership and participation in the SUS as an inpatient care provider.…”