As many vaccines are under Emergency Use Authorization (EUA), understanding the incidence rates of adverse events is critical to providing education and awareness, while working to increase distribution.
Well into 18 months of the COVID-19 pandemic, we are fortunate to have access to several effective vaccines. In the United States, 45% of people are fully vaccinated and 55% of those 18 and up are fully vaccinated.
Some states in the United States have 60% or more adults fully vaccinated, which is a very privileged place to be. While we have a lot of work to do within the US, novel variants like Delta, have underscored that global vaccine distribution is critical to controlling COVID-19.
Globally, there have been nearly 2.6 billion doses administered, which is roughly 34 doses for every 100 people. While countries like the United States, Canada, and the United Kingdom have made great strides in vaccinating their population, far more countries have struggled to gain access to vaccines and then distribute them. As many vaccines are under Emergency Use Authorization (EUA) and vaccine hesitancy is something we struggled with pre-COVID, understanding the incidence rates of adverse events is critical to providing education and awareness, while working to increase distribution.
A new research study was recently published in The BMJ, addressing the characteristics of those background adverse events of special interest for COVID-19 vaccines across eight countries.
The research team performed a multinational network cohort study characterizing 15 adverse events of special interest (AESIs) associated with COVID-19 vaccines. Utilizing electronic medical records and health claims data, they studied 126,661,070 people for at least a day prior to 2019.
Adverse events of special interest were non-hemorrhagic and hemorrhagic stroke, acute myocardial infarction, deep vein thrombosis, pulmonary embolism, anaphylaxis, Bell’s palsy, myocarditis or pericarditis, narcolepsy, appendicitis, immune thrombocytopenia, disseminated intravascular coagulation, encephalomyelitis (including acute disseminated encephalomyelitis), Guillain-Barré syndrome, and transverse myelitis).
Stratified by age, database, and sex, the authors found pretty significant variations of AESI rates across age and sex. They noted that “Background rates varied greatly between databases.
Deep vein thrombosis ranged from 387 (95% confidence interval 370 to 404) per 100 000 person years in UK CPRD GOLD data to 1443 (1416 to 1470) per 100 000 person years in US IBM MarketScan Multi-State Medicaid data among women aged 65 to 74 years. Some AESIs increased with age. For example, myocardial infarction rates in men increased from 28 (27 to 29) per 100 000 person years among those aged 18-34 years to 1400 (1374 to 1427) per 100 000 person years in those older than 85 years in US Optum electronic health record data. Other AESIs were more common in young people. For example, rates of anaphylaxis among boys and men were 78 (75 to 80) per 100 000 person years in those aged 6-17 years and 8 (6 to 10) per 100 000 person years in those older than 85 years in Optum electronic health record data. Meta-analytic estimates of AESI rates were classified according to age and sex.”
The authors noted considerable population heterogeneity in AESI rates, emphasizing the need for more research into these events and trends at individual levels. This description epidemiology of AESIs for COVID-19 vaccines is a critical piece to not only understanding incidence rates of such events, but also being able to speak to them and educate effectively to address vaccine hesitancy.