These data are preliminary, based on surveillance data, and should be interpreted with caution. The results have several limitations:
While this method has been used to assess risk of death following COVID-19 vaccination,2 it violates the assumption that an event does not affect subsequent exposure (for mRNA vaccines), which may introduce bias.6 Further, it does not consider the multidose vaccination schedule required for mRNA vaccination.
This study cannot determine the causative nature of a participant’s death. We used death certificate data and not medical records. COVID testing status was unknown for those who did not die of/with COVID. Cardiac-related deaths were ascertained if an ACME code of I3-I52 were on their death certificate, thus, the underlying cause of death may not be cardiac-related.
The finding that the Janssen vaccine was more protective than mRNA vaccine against mortality within 28 days of vaccination could be due to confounding and needs to be further evaluated. It is likely that the populations who received COVID-19 mRNA vaccine and the Johnson vaccine are different, something we were not able to ascertain in this analysis. It is possible that the population who received the Johnson vaccine was younger and healthier than those receiving the mRNA vaccines. The Pfizer and Moderna mRNA vaccines were released more than 2 months earlier than the Janssen vaccine when the recommendations were limited to those 65 and older.
Additional studies should be conducted to further understand the risks and benefits of vaccination of males between 25-39. Increased risk in the primary analysis for the 25 - 39 age group was based on a small sample size. Additionally, significant mortality from diagnosed COVID-19 infection occurred among all adult age groups. COVID-19 mortality among asymptomatic or undiagnosed COVID-19 infection is less clear. However, excess overall mortality among 25–44-year-old Americans was significant in a study1 looking at mortality from January 2020-October 2020. The largest increases were among Hispanic and Latino. It is unclear what the contribution of asymptomatic or undiagnosed COVID-19 infection is to mortality risk, and how this contributes to excess mortality.