Assessment of long-term adverse events regarding different COVID-19 vaccine regimens within an 18-month follow-up study.

Early reports on COVID-19 vaccines presented the short-term adverse events (AEs). This follow-up study investigated a standard regimen based on protein subunit vaccines, PastoCovac and PastoCovac Plus, and the combinational vaccine regimens including AstraZeneca/PastoCovac Plus and Sinopharm/PastoCovac Plus. The participants were followed up to 6 months post-the booster shot. All the AEs were collected through in-depth interview using a valid researcher-made questionnaire and were evaluated regarding the association with the vaccines. Of the 509 individuals, 6.2% of the combinational vaccine participants had late AEs from whom 3.3% suffered from cutaneous manifestations followed by 1.1% arthralgia complains, 1.1% with neurologic disorders, 0.3% ocular problem and 0.3% metabolic complication, with no significant difference between the vaccine regimens. Of the standard regimen, 2% of the individuals experienced late AEs as (1%), neurologic disorders (0.3%), metabolic problem (0.3%) and joints involvements (0.3%). Notably, 75% of the AEs were persistent up to the end of the study. A low number of late AEs were captured in 18 months as 12 improbable, 5 unclassifiable, 4 possible and 3 probable associated AEs with the vaccine regimens. The benefits of COVID-19 vaccination are far from the potential risks and the late AEs seem to be uncommon.