The number of individuals developing rare blood clotting disorders after getting AstraZeneca or mRNA vaccine is lower when compared with expected rates in the general population and in those infected with COVID-19, real-world study shows.
Citing a population-based cohort study of over one million individuals, published as a pre-print on The Lancet server, very rare clotting disorder thrombosis with thrombocytopenia (TTS) following vaccination were observed with both vaccines but “these were in line with what would be expected in the general population and lower than in those diagnosed with COVID-19”.
Follow-up time was not sufficient to report rates after two doses of AstraZeneca’s COVID-19 vaccine, though other studies have shown rates of rare blood clotting events to be lower after a second dose.
Regardless of the vaccine used, the increase in rates of thrombosis among persons infected with COVID-19 was far higher than among those vaccinated, AstraZeneca said. Rates of venous thromboembolism were eight times higher after a diagnosis of COVID-19 infection compared with the expected rate.
The analysis included 945,941 mRNA participants (778,534 with two doses) and 426,272 AstraZeneca’s COVID-19 vaccine participants, conducted between December 27, 2020 and May 19, 2021. It also included 222,710 COVID-19 participants identified between Sept. 1, 2020 and March 1, 2021, and 4,570,149 background participants as of January 1, 2017 from a public health database held in Catalonia, Spain.
“This real-world study offers further evidence of the favorable benefit:risk profile of AstraZeneca’s COVID-19 vaccine and demonstrates the critical role all COVID-19 vaccines are playing in combatting the pandemic,” said Mene Pangalos, executive vice president of BioPharmaceuticals R&D.
The country president of AstraZeneca Philippines said in an interview last week that more than 15 million doses of AstraZeneca vaccine were expected to arrive in the country this year until early 2022.