Abstract:
OBJECTIVE : To assess the rates of vascular
thrombotic adverse events in the first 35 days after
one dose of the Ad26.COV2.S vaccine (Janssen/
Johnson & Johnson) in healthcare workers in South
Africa and to compare these rates with those
observed in the general population.
DESIGN : Open label, single arm, phase 3B study.
SETTING : Sisonke study, South Africa, 17 February to
15 June 2021.
PARTICIPANTS : The Sisonke cohort of 477 234
healthcare workers, aged ≥18 years, who received
one dose of the Ad26.COV2.S vaccine.
MAIN OUTCOME MEASURES : Observed rates of
venous arterial thromboembolism and vaccine
induced immune thrombocytopenia and thrombosis
in individuals who were vaccinated, compared
with expected rates, based on age and sex specific
background rates from the Clinical Practice Research
Datalink GOLD database (database of longitudinal
routinely collected electronic health records from UK
primary care practices using Vision general practice
patient management software).
RESULTS : Most of the study participants were
women (74.9%) and median age was 42 years
(interquartile range 33-51).
Twenty nine (30.6 per
100 000 person years, 95% confidence interval
20.5 to 44.0) vascular thrombotic events occurred
at a median of 14 days (7-29)
after vaccination. Of
these 29 participants, 93.1% were women, median
age 46 (37-55)
years, and 51.7% had comorbidities.
The observed to expected ratios for cerebral venous
sinus thrombosis with thrombocytopenia and
pulmonary embolism with thrombocytopenia were
10.6 (95% confidence interval 0.3 to 58.8) and
1.2 (0.1 to 6.5), respectively. Because of the small
number of adverse events and wide confidence
intervals, no conclusions were drawn between these
estimates and the expected incidence rates in the
population.
CONCLUSIONS : Vaccine induced immune
thrombocytopenia and thrombosis after one dose
of the Ad26.COV2.S vaccine was found in only a
few patients in this South African population of
healthcare workers. These findings are reassuring
if considered in terms of the beneficial effects of
vaccination against covid-19
disease. These data
support the continued use of this vaccine, but
surveillance is recommended to identify other
incidences of venous and arterial thromboembolism
and to improve confidence in the data estimates.
TRIAL REGISTRATION : ClinicalTrials. gov
NCT04838795.
