• Since 2020, when COVID-19 was declared a pandemic, more than 13.5 billion doses of COVID-19 vaccines have been administered.

• Following this, in 2020, the Safety Platform for Emergency vACcines (SPEAC) listed the potential Adverse Events of Special Interest (AESI).

• A retrospective multi-centric observational study was conducted to estimate the selected AESIs after vaccination.

• The study compared the observed AESI (OE) rates following vaccination with the expected rates based on pre-vaccine rollout data.

• The study period ranged from December 2020 to August 2023 and included 13 selected AESIs.

• Three vaccines with the highest number of administered doses were included, which were as follows:

• 1. Pfizer/BioNTech BNT162b2

• 2. Moderna Mrna-1273

• 3. Oxford/Astra Zeneca ChAdOx1

• During the study period, 99 million doses were administered, and 23,168,335 person-years contributed to the OE ratios for the AESI.

• The following conditions had OEs, that were statistically different from the expected rates:

1. Following the first dose of Astra Zeneca: Guillian-Barre syndrome and Cerebral venous sinus thrombosis

2. Acute disseminated encephalomyelitis following the first dose of mRNA vaccines

3. Myocarditis and pericarditis following all three vaccines.

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