In a recent article published in E.g. Vaccines, investigators are examining the comparative risk of ischemic stroke (IS) in individuals who received booster doses of bivalent or monovalent coronavirus disease 2019 (COVID-19) vaccines at age ≥ 65 years.
Test: Ischemic stroke following administration of bivalent COVID-19 vaccine to patients 65 years of age and older in the USA. Photo credit: Wachiwit/Shutterstock.com
Background
The Centers for Disease Control and Prevention’s (CDC) announcement that Pfizer’s bivalent COVID-19 vaccine increases the chance of IS inside three weeks of receipt was unexpected since it didn’t raise any concerns about previously receiving the Moderna bivalent vaccine.
Moreover, the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) found no higher risk of IS for the Pfizer bivalent vaccine.
It could due to this fact represent the next incidence of pre-existing comorbidities (IS risk aspects) amongst patients who received the Pfizer bivalent booster in comparison with the monovalent booster.
Nevertheless, there’s a necessity to analyze the comparative risk of IS amongst recipients of bivalent and monovalent Covid-19 vaccines in response to those inconsistent reports from vital health agencies and given their widespread use in older adults aged 65 years and older in the USA (US). .
In regards to the study
Researchers conducted this retrospective cohort study using de-identified electronic health data from people aged ≥ 65 years from TriNetX, a cloud-based analytics platform within the US.
These people received a bivalent or monovalent Covid-19 vaccine booster from Pfizer or Moderna by August 27, 2023.
Due to this fact, the Pfizer bivalent booster, Moderna bivalent booster, and monovalent booster groups included 110,667, 26,962, and 96,156 recipients, respectively.
After propensity rating matching, all matched cohorts consisted of 26,962 patients, for whom investigators used Kaplan-Meier survival evaluation to estimate the probability of a selected end result (on this case IS) at two different time intervals (1-21 days and 22-42 days). after the booster dose.
Results are presented as hazard ratios (HR) and 95% confidence intervals (CI). Furthermore, on this evaluation they censored patients to forestall bias in estimating the probability of IS.
They performed all statistical tests inside the TriNetX Analytics platform, setting the importance level at a p-value (two-sided) <0.05.
Moreover, investigators performed a subanalysis to match the chance of first-time IS between the Pfizer bivalent and monovalent booster cohorts (only).
Results
Researchers noted a reduced risk of IS diagnosis within the Pfizer bivalent cohort compared with the monovalent cohort (N = 79,036 patients per cohort) at each time points assessed. Between days 1 and 21 after vaccination, the HR was 0.54, 95% CI, and between days 22 and 42 after vaccination, the HR was 0.62, 95% CI.
Even in comparison with the Moderna bivalent cohort, the Pfizer bivalent cohort showed a reduced risk of IS, with HR: 0.75, 95% CI at 1–21 days after vaccination. Each cohorts had 26,962 patients per cohort.
They cited two possible reasons for the reduced risk of being diagnosed with an IS encounter in recipients of the bivalent Pfizer booster. First, bivalent booster doses provide simpler protection against serious Covid-19 infection and associated hospitalization.
Second, throughout the period of widespread administration of those vaccines, Omicron, a variant of severe acute respiratory tract virus 2 (SARS-CoV-2), which causes a less severe infection, predominated as booster doses.
The chance of being diagnosed with an IS encounter within the Pfizer bivalent cohort was significantly reduced compared with the Moderna bivalent cohorts over the 1–21 day timeframe.
Nevertheless, there was no clear difference in the chance of first-time IS diagnosis in each bivalent and monovalent Pfizer vaccine recipients.
Furthermore, it’s price noting that severe COVID-19 may further increase the chance of one other stroke in patients who’ve previously had a stroke as a consequence of inflammatory and vascular aspects.
Reports also documented cases of IS related to vaccine-related immune thrombotic thrombocytopenia, which may additionally have occurred in some individuals within the study cohorts.
The CDC warned of a potentially increased risk of IS inside three weeks of administering bivalent Pfizer boosters. Nevertheless, each cohorts were older and had multiple comorbidities comparable to obesity, hypertension, dyslipidemia, type 2 diabetes, and cerebrovascular disease.
Given the high incidence of IS in the final US population, it is probably going that the etiology of those strokes were risk aspects for IS, no matter whether people had received any COVID-19 vaccine.
Conclusions
In conclusion, the study results don’t support that U.S. individuals ≥65 years of age are at increased risk of developing IS after receiving the Pfizer bivalent booster vaccine, because the CDC predicted in its report, especially in comparison with the Moderna monovalent or bivalent vaccines.
Due to this fact, all healthcare staff and older people (65+) shouldn’t feel discouraged from administering or receiving this booster vaccine.