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Background: Drug overdose deaths in the USA have increased rapidly in the past 20 years, and understanding patterns and trends in mortality is essential to develop policy responses. This study aimed to determine whether cohort patterns in mortality due to drug overdose have changed in the past two decades and assess these patterns by race and sex. Methods: The national records of accidental drug overdose death were extracted from Centers for Disease Control and Prevention, National Center for Health Statistics Mortality Data for 2000-2020. Age-period-cohort analysis was performed to examine independent effects of age, period and birth cohort on accidental drug overdose mortality. Findings: The number of accidental drug overdose deaths increased by 622% between 2000 and 2020, and age-standardized mortality rates increased nearly four-fold in both men and women. Age-period-cohort decomposition found rapid increases in mortality since 2012 in men and women, with higher mortality risk in cohorts born after 1990. The fastest increase occurred in Black Americans since 2012, and Americans of all races born after 1975 had significantly higher mortality risk, with mortality risk increasing rapidly in more recent cohorts. The peak of mortality has shifted from the 40-59 age group to the 30-40 year age group in the past decade. Interpretation: The burden of drug overdose mortality has shifted to younger Americans, and a new generation of Americans are at significantly higher and rapidly increasing risk of overdose death. Urgent action is needed to prevent an entire generation of young people being consigned to decades of preventable mortality. Funding: None.
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OBJECTIVES: The rapid spread of the SARS-CoV-2 Omicron variant has raised concerns regarding waning vaccine-induced immunity and durability. We evaluated protection of the third-dose and fourth-dose mRNA vaccines against SARS-CoV-2 Omicron subvariant and its sublineages. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Electronic databases and other resources (PubMed, Embase, CENTRAL, MEDLINE, CINAHL PLUS, APA PsycINFO, Web of Science, Scopus, ScienceDirect, MedRxiv and bioRxiv) were searched until December 2022. STUDY ELIGIBILITY CRITERIA: We included studies that assessed the effectiveness of mRNA vaccine booster doses against SARS-CoV-2 infection and severe COVID-19 outcomes caused by the subvariant. DATA EXTRACTION AND SYNTHESIS: Estimates of vaccine effectiveness (VE) at different time points after the third-dose and fourth-dose vaccination were extracted. Random-effects meta-analysis was used to compare VE of the third dose versus the primary series, no vaccination and the fourth dose at different time points. The certainty of the evidence was assessed by Grading of Recommendations, Assessments, Development and Evaluation approach. RESULTS: This review included 50 studies. The third-dose VE, compared with the primary series, against SARS-CoV-2 infection was 48.86% (95% CI 44.90% to 52.82%, low certainty) at ≥14 days, and gradually decreased to 38.01% (95% CI 13.90% to 62.13%, very low certainty) at ≥90 days after the third-dose vaccination. The fourth-dose VE peaked at 14-30 days (56.70% (95% CI 50.36% to 63.04%), moderate certainty), then quickly declined at 61-90 days (22% (95% CI 6.40% to 37.60%), low certainty). Compared with no vaccination, the third-dose VE was 75.84% (95% CI 40.56% to 111.12%, low certainty) against BA.1 infection, and 70.41% (95% CI 49.94% to 90.88%, low certainty) against BA.2 infection at ≥7 days after the third-dose vaccination. The third-dose VE against hospitalisation remained stable over time and maintained 79.30% (95% CI 58.65% to 99.94%, moderate certainty) at 91-120 days. The fourth-dose VE up to 60 days was 67.54% (95% CI 59.76% to 75.33%, moderate certainty) for hospitalisation and 77.88% (95% CI 72.55% to 83.21%, moderate certainty) for death. CONCLUSION: The boosters provided substantial protection against severe COVID-19 outcomes for at least 6 months, although the duration of protection remains uncertain, suggesting the need for a booster dose within 6 months of the third-dose or fourth-dose vaccination. However, the certainty of evidence in our VE estimates varied from very low to moderate, indicating significant heterogeneity among studies that should be considered when interpreting the findings for public health policies. PROSPERO REGISTRATION NUMBER: CRD42023376698.