(248) Prospective Monitoring of COVID-19 Vaccine Safety in the Republic of Croatia

Publication Number: 1293

Background: Post-marketing monitoring of vaccine safety and timely detection of potential signals and suppression of false claims is important to maintain public confidence in the vaccination program. Considering importance of COVID-19 vaccines, and public interest in them, it was concluded that intensive monitoring of the COVID-19 vaccines would be an important addition to the existing spontaneous reporting system in Croatia.

Objectives: The primary objective of this study is to describe the patterns of COVID-19 vaccines’ AEFIs (e.g. type of AEFI, seriousness, outcome) based on the responses from vaccinees in near real time.

Methods: We performed prospective cohort study, which has started in February 2021. According to inclusion criteria all vaccinated recipients, including children 12 -17 years old, could participate in the study no later than six days after receiving the first or third dose of the vaccine, regardless of the vaccine they received. An online platform OPeN, developed by HALMED, is used for data collection and AEFI reporting.

Results: 368 vaccinated persons were included in the study until the end of January 2022. Majority were female (77%), and median age was 37 years-old. No children were included, and only 2 participants were elderly (≥65 years). As a primary vaccination, most participants received Comirnaty (272), followed by Vaxzevria (51), Spikevax (28), and COVID-19 Vaccine Janssen (17). 957 AEFIs were reported following primary vaccination, out of which 861 were expected and non-serious, and only 3 AEFIs were unexpected and serious (arrhythmia, hallucination and relaps of seronegative arthritis). 34 participants provided information on booster dose, out of which 28 received Comirnaty, and 6 Spikevax. 24 of them reported 45 AEFIs, all expected and non-serious. 5 pregnant women were included in the study. 3 of them received Comirnaty as primary vaccination, and 2 of them as booster dose during pregnancy. None reported unexpected or serious AEFIs. All 3 participants receiving Comirnaty as primary vaccination gave birth to live-born neonates, and only one neonate had to be received on neonatal intensive care unit due to jaundice. 45 days after the birth, all 3 newborns were healthy.

Conclusions: Our preliminary study results did not identify new safety issues, and are in line with known safety profiles of COVID-19 vaccines approved in EU.